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Thyroid and Parathyroid Agents 37

Learning Objectives Upon completion of this chapter, you will be able to:

1. Explain the control of the synthesis and secretion of thyroid hormones and parathyroid hor- mones, applying this to alterations in the control process (e.g., using thyroid hormones to treat obesity, Paget disease, etc.). 2. Describe the therapeutic actions, indications, pharmacokinetics, contraindications, most common adverse reactions, and important drug–drug interactions associated with thyroid and parathyroid agents. 3. Discuss the use of thyroid and parathyroid drugs across the lifespan. 4. Compare and contrast thyroid and parathyroid prototype drugs with agents in their class. 5. Outline nursing considerations, including important teaching points, for patients receiving drugs used to affect thyroid or parathyroid function.

Glossary of Key Terms bisphosphonates: drugs used to block bone resorption and hypocalcemia: calcium deficienc lower serum calcium levels in several conditions hypoparathyroidism: rare condition of absence of parathor- calcitonin: hormone produced by the parafollicular cells of mone; may be seen after thyroidectomy the thyroid; counteracts the effects of parathyroid hormone hypothyroidism: lack of sufficient thy oid hormone to main- to maintain calcium levels tain metabolism cretinism: lack of thyroid hormone in an infant; if untreated, iodine: important dietary element used by the thyroid gland leads to mental retardation to produce thyroid hormone

follicles: structural unit of the thyroid gland; cells arranged in levothyroxine: a synthetic salt of thyroxine (T4), a thyroid a circle hormone; the most frequently used replacement hormone hypercalcemia: excessive calcium levels in the blood for treating thyroid disease

hyperparathyroidism: excessive parathormone liothyronine: the L-isomer of triiodothyronine (T3), and the hyperthyroidism: excessive levels of thyroid hormone most potent thyroid hormone, with a short half-life of 12 (glossary continues on page 564)

THYROID AGENTS Iodine Solutions Antihypercalcemic Calcitonins sodium iodide I131 calcitonin salmon Thyroid Hormones Agents strong iodine solution, levothyroxine Bisphosphonates potassium iodide liothyronine alendronate liotrix etidronate thyroid desiccated PARATHYROID ibandronate AGENTS pamidronate Antithyroid Agents Antihypocalcemic risedronate Thioamides Agents tiludronate methimazole calcitriol zoledronic acid propylthiouracil dihydrotachysterol teriparatide

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hours Glossary of Key Terms(continued) junction with calcitonin metabolism: rate at which the cells burn energy postmenopausal osteoporosis: condition in which dropping myxedema: severe lack of thyroid hormone in adults levels of estrogen allow calcium to be pulled out of the bone, Paget disease: a genetically linked disorder of overactive resulting in a weakened and honeycombed bone structure osteoclasts that are eventually replaced by enlarged and thioamides: drugs used to prevent the formation of thyroid softened bony structures hormone in the thyroid cells, lowering thyroid hormone levels parathormone: hormone produced by the parathyroid thyroxine: a thyroid hormone that is converted to triiodothy- glands; responsible for maintaining calcium levels in con-

his chapter reviews drugs that are used to affect the func- comes from the Greek words thyros (shield) and eidos (gland). T tion of the thyroid and parathyroid glands. These tw o It produces two hormones—thyroid hormone and calcitonin. glands are closely situated in the middle of the neck and share a common goal of calcium homeostasis. Serum calcium le v- Structure and Function els need to be maintained within a narro w range to promote effective blood coagulation, as well as nerv e and muscle The thyroid is a vascular gland with two lobes—one on each function. In most respects, however, these glands are v ery side of the trachea—and a small isthmus connecting the different in structure and function. lobes. The gland is made up of cells arranged in circular fol- licles. The center of each follicle is composed of colloid tis- sue, in which the thyroid hormones produced by the gland are THE THYROID GLAND stored. Cells found around the follicle of the thyroid gland are called parafollicular cells (see Figure 37.1). These cells pro- The thyroid gland is located in the middle of the neck, where duce another hormone,calcitonin, which affects calcium lev- it surrounds the trachea lik e a shield (Figure 37.1). Its name els and acts to balance the effects of the parathyroid hormone

Thyroid cells Parafollicular cells

Thyroid follicles Colloid

Thioamides, iodines work here

Blood vessel

Thyroid replacement hormone replaces hormones from colloid Thyroid gland when levels are low Trachea

Parathyroid glands

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CHAPTER 37 Thyroid and Parathyroid Agents 565

(PTH), parathormone. Calcitonin will be discussed later in connection with the parathyroid glands. The thyroid gland produces two slightly different thyroid Hypothalamus hormones, using iodine that is found in the diet:thyroxine, or

tetraiodothyronine (T 4), so named because it contains four iodine atoms, which is given therapeutically in the synthetic TRH form levothyroxine, and triiodothyronine (T 3), so named because it contains three iodine atoms, which is given in the synthetic form liothyronine. The thyroid cells remove iodine from the blood, concentrate it, and prepare it for attachment to tyrosine, an amino acid. A person must obtain suf ficien amounts of dietary iodine to produce thyroid hormones. The thyroid hormone regulates the rate of metabolism—that is, Posterior Anterior the rate at which energy is burned—in almost all the cells of pituitary pituitary the body. The thyroid hormones af fect heat production and body temperature; oxygen consumption and cardiac output; blood volume; enzyme system acti vity; and metabolism of carbohydrates, fats, and proteins. Thyroid hormone is also an TSH levels

important regulator of gro wth and de velopment, especially 4 , T

within the reproductive and nervous systems. Because the 3 thyroid has such widespread effects throughout the body, any dysfunction of the thyroid gland will ha ve numerous sys- temic effects.

When thyroid hormone is needed in the body , the stored T Insufficient thyroid hormone molecule is absorbed into the thyroid cells, levels where the T3 and T4 are broken off and released into circula- 4 , T tion. These hormones are carried on plasma proteins, which Thyroid 3 can be measured as protein-bound iodine (PBI) le vels. The gland

thyroid gland produces more T4 than T3. More T4 is released into circulation, but T is approximately four times more 3 Adequate T active than T4. Most T4 (with a half-life of about 12 hours) is T , T 3 4 converted to T3 (with a half-life of about 1 week) at the tissue level. Stimulates Inhibits

Control ● FIGURE 37.2 In response to low blood serum levels of thyroid hor- Thyroid hormone production and release are regulated by the mone, the hypothalamus sends the thyrotropin-releasing hormone anterior pituitary hormone called thyroid-stimulating hormone (TRH) to the anterior pituitary, which responds by releasing the thy- (TSH). The secretion of TSH is re gulated by thyrotropin- roid-stimulating hormone (TSH) to the thyroid gland; it, in turn, responds by releasing the thyroid hormone (T3 and T4) into the releasing hormone (TRH), a hypothalamic regulating factor. bloodstream. The anterior pituitary is also sensitive to the increase in A delicate balance exists among the thyroid,the pituitary, and blood serum levels of the thyroid hormone and responds by decreas- the hypothalamus in regulating the levels of thyroid hormone. ing production and release of TSH. As thyroid hormone production and release subside, the hypothalamus senses the lower serum lev- See Chapter 36 for a review of the negative feedback system els, and the process is repeated by the release of TRH again. This and the hypothalamic–pituitary axis. The thyroid gland pro- intricate series of negative feedback mechanisms keeps the level of duces increased thyroid hormones in response to increased thyroid hormone within normal limits. levels of TSH. The increased levels of thyroid hormones send a negative feedback message to the pituitary to decrease TSH release and, at the same time, to the hypothalamus to decrease series of ne gative feedback mechanisms k eeps the le vel of TRH release. A drop in TRH levels subsequently results in a thyroid hormone within a narrow range of normal (Figure 37.2). drop in TSH levels, which in turn leads to a drop in thyroid hormone levels. In response to low blood serum levels of thy- Thyroid Dysfunction roid hormone, the hypothalamus sends TRH to the anterior pituitary, which responds by releasing TSH, which in turn Thyroid dysfunction involves either underactivity (hypothy- stimulates the thyroid gland to again produce and release thy- roidism) or overactivity (hyperthyroidism). This dysfunction roid hormone. The rising levels of thyroid hormone are sensed can affect any age group. Box 37.1 e xplains use of thyroid by the hypothalamus, and the cycle begins again. This intricate agents across the lifespan. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 566 Aptara

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BOX 37.1 Drug Therapy Across the Lifespan

Thyroid and Parathyroid Agents

CHILDREN If an antithyroid drug is essential during pregnancy, PTU is Thyroid replacement therapy is required when a child is the drug of choice because it is less likely to cross the pla- hypothyroid. Levothyroxine is the drug of choice in children. centa and cause problems for the fetus. Radioactive agents Dose is determined based on serum thyroid hormone levels should not be used. Bisphosphonates should be used during and the response of the child, including growth and devel- pregnancy only if the benefit to the mother clearly out opment. Dose in children tends to be higher than in adults weighs the potential risk to the fetus. Nursing mothers who because of the higher metabolic rate of the growing child. need thyroid replacement therapy should continue with their Usually, the starting dose to consider is 10 to 15 mcg/kg per prescribed regimen and report any adverse reactions in the day. baby. Bisphosphonates and antithyroid drugs should not be Regular monitoring, including growth records, is necessary used during lactation because of the potential for adverse to determine the accurate dose as the child grows. reactions in the baby; another method of feeding the baby Maintenance levels at the adult dose usually occurs after should be used. puberty and when active growing stops. If an antithyroid agent is needed, propylthiouracil (PTU) is OLDER ADULTS the drug of choice because it is less toxic. Unless other Because the signs and symptoms of thyroid disease mimic agents are ineffective, radioactive agents are not used in many other problems that are common to older adults—hair children because of the effects of radiation on chromo- loss, slurred speech, fluid retention, heart failure, and so on somes and developing cells. it is important to screen older adults for thyroid disease care- Hypercalcemia is relatively rare in children, although it fully before beginning any therapy. The dose should be may be seen with certain malignancies. If a child develops a started at a very low level and increased based on the malignancy-related hypercalcemia, the bisphosphonates patient response. Levothyroxine is the drug of choice for may be used, with dose adjustments based on age and hypothyroidism. Periodic monitoring of thyroid hormone lev- weight. Serum calcium levels should be monitored very els, as well as cardiac and other responses, is essential with closely in the child and dose adjustments made as necessary. this age group. If antithyroid agents are needed, sodium iodide I131 may ADULTS be the drug of choice because it has fewer adverse effects Adults who require thyroid replacement therapy need to than the other agents and surgery. The patient should be understand that this will be a lifelong replacement need. An monitored closely for the development of hypothyroidism, established routine of taking the tablet first thing in the mo n- which usually occurs within a year after initiation of antithy- ing may help the patient to comply with the drug regimen. roid therapy. Levothyroxine is the drug of choice for replacement, but in Older adults may have dietary deficiencies related t some cases other agents may be needed. Periodic monitor- calcium and vitamin D. They should be encouraged to eat ing of thyroid hormone levels is necessary to ensure that dose dairy products and foods high in calcium and to supple- needs have not changed. ment their diet if necessary. Postmenopausal women, who If antithyroid drugs are needed, the patient’s underlying are prone to develop osteoporosis, may want to consider problems should be considered. Methimazole is associated hormone replacement therapy and calcium supplements with bone marrow suppression and more gastrointestinal to prevent osteoporosis. Many postmenopausal women, and central nervous system effects than is PTU. Sodium and some older men, respond well to the effect of bisphos- iodide I131 should not be used in adults in their reproductive phonates in moving calcium back into the bone. They years unless they are aware of the possibility of adverse need specific instructions on the proper way to take thes effects on fertility. drugs and may not be able to comply with the restrictions Alendronate and risedronate are commonly used drugs about staying upright and swallowing the tablet with a full for osteoporosis and calcium lowering. Serum calcium levels glass of water. need to be monitored carefully with any of the drugs that Older adults have a greater incidence of renal impair- affect calcium levels. Patients should be encouraged to take ment, and kidney function should be evaluated before calcium and vitamin D in their diet or as supplements in starting any of these drugs. Bisphosphonates should be cases of hypocalcemia, and also for prevention and treat- used in lower doses in patients with moderate renal impair- ment of osteoporosis. ment and are not recommended for those who have Thyroid replacement therapy is necessary during preg- severe renal impairment. With any of these drugs, regular nancy for women who have been maintained on this regi- monitoring of calcium levels is important to ensure that men. It is not uncommon for hypothyroidism to develop dur- therapeutic effects are achieved with a minimum of ing pregnancy. Levothyroxine is again the drug of choice. adverse effects. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 567 Aptara

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Hypothyroidism of autoimmune thyroid disease (Hashimoto disease), viral Hypothyroidism is a lack of sufficient l vels of thyroid hor- infection, or overtreatment with antithyroid drugs or because mones to maintain a normal metabolism. This condition of sur gical remo val or irradiation of the thyroid gland. occurs in a number of pathophysiological states: Patients with myxedema exhibit many signs and symptoms. Hypothyroidism is treated with replacement thyroid hormone • Absence of the thyroid gland therapy. • Lack of sufficient iodine in the diet to produce the neede level of thyroid hormone Hyperthyroidism • Lack of sufficient functioning thyroid tissue due to tumo Hyperthyroidism occurs when excessive amounts of thyroid or autoimmune disorders hormones are produced and released into the circulation. • Lack of TSH due to pituitary disease Graves disease, a poorly understood condition that is thought • Lack of TRH related to a tumor or disorder of the to be an autoimmune problem, is the most common cause of hypothalamus hyperthyroidism. Goiter (enlargement of the thyroid gland) is Hypothyroidism is the most common type of thyroid dys- an effect of hyperthyroidism, which occurs when the thyroid function. It is estimated that approximately 5% to 10% of is overstimulated by TSH. This can happen if the thyroid gland women older than 50 years of age are hypothyroid. Hypo- does not mak e suf ficient thyroid hormones to turn o f the thyroidism is also a common finding in elderly men. The hypothalamus and anterior pituitary; in the body’s attempt to symptoms of hypothyroidism can be v aried and vague, such produce the needed amount of thyroid hormone,the thyroid is as obesity and f atigue (Box 37.2), and are frequently o ver- continually stimulated by increasing levels of TSH. Additional looked or mistaken for signs of normal aging (Table 37.1). signs and symptoms of hyperthyroidism can be found in Children who are born without a thyroid gland or who Table 37.1. have a nonfunctioning gland develop a condition called cre- Hyperthyroidism may be treated by surgical removal of the tinism. If untreated, these children will have poor growth and gland or portions of the gland, treatment with radiation to development and mental retardation because of the lack of destroy parts or all of the gland,or drug treatment to block the thyroid hormone stimulation. Severe adult hypothyroidism is production of thyroxine in the thyroid gland or to destro y called myxedema. Myxedema usually develops gradually as parts or all of the gland. The metabolism of these patients then the thyroid slowly stops functioning. It can develop as a result must be regulated with replacement thyroid hormone therapy.

BOX 37.2 The Evidence

Thyroid Hormones for Obesity

Treatment trends for obesity have changed over the years. endocrine imbalance. What’s more, they also did not lose Not long ago, one of the suggested treatments was the use weight—and in the long run may actually have gained of thyroid hormone. The thinking was that obese people had weight as the body’s compensatory mechanisms tried to slower metabolisms and therefore would benefit from deal with the imbalances. boost in metabolism from extra thyroid hormone. Today, thyroid hormone is no longer considered a good If an obese patient is truly hypothyroid, this might be a choice for treating obesity. Other drugs have come and good idea. Unfortunately, many of the patients who gone, and new drugs are released each year to attack received thyroid hormone for weight loss were not tested for other aspects of the problem. Many patients, especially mid- thyroid activity and ended up with excessive thyroid hor- dle-aged people who may recall that thyroid hormone was mone in their systems. This situation triggered a cascade of once used for weight loss, ask for it as an answer to their events. The exogenous thyroid hormone disrupted the hypo- weight problem. Patients have even been known to “bor- thalamic–pituitary–thyroid control system, resulting in row” thyroid replacement hormones from others for a quick decreased production of thyrotropin-releasing hormone weight loss solution or to order the drug over the Internet (TRH) and thyroid-stimulating hormone (TSH) as the hypothal- without supervision or monitoring. amus and pituitary sensed the rising levels of thyroid hor- Obese patients need reassurance, understanding, and mone. Because the thyroid was no longer stimulated to pro- education about the risks of borrowed thyroid hormone. duce and secrete thyroid hormone, thyroid levels would Insistent patients should undergo thyroid function tests. If the actually fall. Lacking stimulation by TSH, the thyroid gland results are normal, patients should receive teaching about would start to atrophy. If exogenous thyroid hormone were the controls and actions of thyroid hormone in the body and stopped, the atrophied thyroid would not be able to imme- an explanation of why taking these hormones can cause diately respond to the TSH stimulation and produce thyroid problems. Obesity is a chronic and frustrating problem that hormone. Ultimately, these patients experienced an poses continual challenges for health care providers. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 568 Aptara

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● TABLE 37.1 Signs and Symptoms of Thyroid Dysfunction

CLINICAL EFFECTS HYPOTHYROIDISM HYPERTHYROIDISM

Central nervous Depressed: hypoactive reflexes, Stimulated: hyperactive reflexes, anxiety, system lethargy, sleepiness, slow speech, nervousness, insomnia, tremors, restlessness, emotional dullness increased basal temperature Cardiovascular Depressed: bradycardia, hypotension, Stimulated: tachycardia, palpitations, system anemia, oliguria, decreased sensitivity increased pulse pressure, systolic hypertension, to catecholamines increased sensitivity to catecholamines Skin, hair, and Skin is pale, coarse, dry, thickened; Skin is flushed, wa m, thin, moist, sweating; nails puffy eyes and eyelids; hair is coarse hair is fine and soft; nails are soft and thi and thin; hair loss; nails are thick and hard Metabolic rate Decreased: lower body temperature; Increased, overactive cellular metabolism: intolerance to cold; decreased low-grade fever; intolerance to heat; appetite, higher levels of fat and increased appetite with weight loss; muscle cholesterol; weight gain; wasting and weakness, thyroid myopathy hypercholesterolemia Generalized Accumulation of mucopolysaccharides Localized with accumulation of myxedema in the heart, tongue, and vocal cords; mucopolysaccharides in eyeballs, ocular periorbital edema, cardiomyopathy, muscles; periorbital edema, lid lag, hoarseness, and thickened speech exophthalmos; pretibial edema Ovaries Decreased function: menorrhagia, Altered; tendency toward oligomenorrhea, habitual abortion, sterility, amenorrhea decreased sexual function Goiter Rare; simple nontoxic type may occur Diffuse, highly vascular; very frequent

KEY POINTS Levothyroxine (Synthroid, Levoxyl, Levothroid), a synthetic ➧ The thyroid gland uses iodine to produce the thyroid hor- salt of T4, is the most frequently used replacement hormone mones that regulate body metabolism. because of its predictable bioa vailability and reliability . ➧ Control of the thyroid gland involves an intricate balance Desiccated thyroid (Armour Thyroid and others) is prepared among TRH, TSH, and circulating levels of thyroid hormone. from dried animal thyroid glands and contains both T3 and ➧ Hypothyroidism is treated with replacement thyroid hor- T4; although the ratio of the hormones is unpredictable and mone; hyperthyroidism is treated with thioamides or iodines. the required dose and ef fects vary widely, this drug is ine x- pensive, making it attractive to some. Additional thyroid hor- mones include liothyronine ( Cytomel, Triostat), a synthetic THYROID AGENTS salt of T3, and liotrix (Thyrolar), a synthetic preparation of T4 and T3 in a standard 4:1 ratio. When thyroid function is lo w, thyroid hormone needs to be replaced to ensure adequate metabolism and homeostasis in Therapeutic Actions and Indications the body. When thyroid function is too high, the resultant systemic effects can be serious, and the thyroid will need to The thyroid replacement hormones increase the metabolic rate be remo ved or destro yed pharmacologically , and then the of body tissues, increasing oxygen consumption, respiration, hormone normally produced by the gland will need to be heart rate, growth and maturation, and the metabolism of fats, replaced with thyroid hormone. Thyroid agents include thyroid carbohydrates, and proteins. They are indicated for replace- hormones and antithyroid drugs,which are further classified a ment therap y in hypothyroid states, treatment of myx edema thioamides and iodine solutions. Table 37.2 includes a com- coma, suppression of TSH in the treatment and pre vention of plete list of each type of thyroid agent. goiters, and management of thyroid cancer . In conjunction with antithyroid drugs, they also are indicated to treat thyroid toxicity, prevent goiter formation during thyroid overstimula- Thyroid Hormones tion, and treat thyroid overstimulation during pregnancy. See Table 37.2 for usual indications for each drug. Several replacement hormone products are available for treating hypothyroidism. These hormones replace the low or Pharmacokinetics absent le vels of natural thyroid hormone and suppress the overproduction of TSH by the pituitary . These products can These drugs are well absorbed from the gastrointestinal (GI) contain both natural and synthetic thyroid hormone. tract and bound to serum proteins. Because it contains only LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 569 Aptara

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TABLE 37.2 DRUGS IN FOCUS Thyroid Agents

Drug Name Dosage/Route Usual Indications

Thyroid Hormones

levothyroxine Adult: 0.05Ð0.2 mg/d PO Replacement therapy in hypothyroidism; suppression (Synthroid, Levoxyl, Pediatric: 0.025Ð0.4 mg/d PO of thyroid-stimulating hormone (TSH) release; Levothroid, others) treatment of myxedema coma and thyrotoxicosis liothyronine Adult: 25Ð100 mcg/d PO Replacement therapy in hypothyroidism; suppression (Cytomel, Triostat) Pediatric: 20Ð50 mcg/d PO of TSH release; treatment of thyrotoxicosis; synthetic hormone used in patients allergic to desiccated thyroid Special considerations: not for use with cardiac or anxiety problems liotrix (Thyrolar) Adult: 60Ð120 mg/d PO Replacement therapy in hypothyroidism; suppression Pediatric: 25Ð150 mcg/d PO based on age of TSH release; treatment of thyrotoxicosis and weight Special considerations: not for use with cardiac dysfunction thyroid desiccated Adult: 60Ð120 mg/d PO Replacement therapy in hypothyroidism; suppression (Armour Thyroid) Pediatric: 15Ð90 mg/d PO of TSH release; treatment of thyrotoxicosis

Antithyroid Agents Thioamides

methimazole Adult: 15 mg/d PO initially, up to Treatment of hyperthyroidism (Tapazole) 30Ð60 mg/d may be needed; maintenance, 5Ð15 mg/d PO Pediatric: 0.4 mg/kg per day PO initially; maintenance, 15Ð20 mg/m2 per day PO in three divided doses propylthiouracil Adult: 300Ð900 mg/d PO initially; Treatment of hyperthyroidism maintenance, 100Ð150 mg/d PO Pediatric: 50Ð300 mg/d PO based on age and response

Iodine solutions

sodium iodide I131 Adult (30 yr): 4Ð10 millicuries PO as Treatment of hyperthyroidism; thyroid blocking in (generic, radioactive needed radiation emergencies; destruction of thyroid tissue in iodine) patients who are not candidates for surgical removal of the gland strong iodine Adult: one tablet, or 2Ð6 drops (gtt) PO Treatment of hyperthyroidism, thyroid blocking in solution, potassium daily to t.i.d. radiation emergencies; presurgical suppression of iodide (Thyro-Block) Pediatric (1 yr): adult dose the thyroid gland, treatment of acute thyrotoxicosis 1 Pediatric (1 yr): ⁄2 tablet or 3 gtt PO until thioamide levels can take effect daily to t.i.d.

T , liothyronine has a rapid onset and a long duration of 3 Contraindications and Cautions action. Deiodination of the drugs occurs at se veral sites, including the liver, kidney, and other body tissues. Elimination These drugs should not be used with any known allergy to the is primarily in the bile. Thyroid hormone does not cross the drugs or their binders to prevent hypersensitivity reactions, placenta and seems to ha ve no ef fect on the fetus. Thyroid during acute thyrotoxicosis (unless used in conjunction with replacement therapy should not be discontinued during preg- antithyroid drugs), or during acute myocardial inf arction nancy, and the need for thyroid replacement often becomes (unless complicated by hypothyroidism) because the thyroid apparent or increases during pre gnancy. Thyroid hormone hormones could exacerbate these conditions. Caution should does enter breast milk in small amounts. Caution should be be used during lactation because the drug enters breast milk used during lactation. and could suppress the infant’s thyroid production, and with LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 570 Aptara

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hypoadrenal conditions such as Addison disease. Liothyronine Nursing Considerations for Patients and liotrix have a greater incidence of cardiac side effects and Receiving Thyroid Hormones are not recommended for use in patients with potential car- diac problems or patients who are prone to anxiety reactions. Assessment: History and Examination • Assess for history of allergy to any thyroid hormone or Adverse Effects binder, lactation, Addison disease, acute myocardial infarction not complicated by hypothyroidism, and thyro- When the correct dose of the replacement therap y is being toxicosis, which could be contraindications or cautions to used, few if any adverse effects are associated with these drugs. use of the drug. Skin reactions and loss of hair are sometimes seen, especially • Assess for the presence of any skin lesions; orientation during the first f w months of treatment in children. Symptoms and affect; baseline pulse, blood pressure, and electrocar- of hyperthyroidism may occur as the drug dose is re gulated. diogram (ECG); respiration and adventitious sounds; and Some of the less predictable ef fects are associated with car- thyroid function tests, to determine baseline status before diac stimulation (arrhythmias, hypertension), central nervous beginning therapy and for any potential adverse effects. system (CNS) effects (anxiety, sleeplessness, headache), and difficulty s allowing (taking the drug with a full glass of Refer to the Critical Thinking Scenario for a full discussion of water may help). nursing care for a patient who is receiving a thyroid hormone.

Nursing Diagnoses Clinically Important Drug–Drug Interactions Nursing diagnoses related to drug therapy might include the Decreased absorption of the thyroid hormones occurs if they following: are taken concurrently with cholestyramine. If this combina- • Decreased Cardiac Output related to cardiac effects tion is needed, the drugs should be taken 2 hours apart. • Imbalanced Nutrition: Less Than Body Requirements The effectiveness of oral anticoagulants is increased if they related to changes in metabolism are combined with thyroid hormone. Because this may lead to • Ineffective Tissue Perfusion related to thyroid activity increased bleeding, the dose of the oral anticoagulant should • Deficient Knowledge regarding drug therapy be reduced and the bleeding time checked periodically. Decreased effectiveness of digitalis glycosides can occur Implementation With Rationale when these drugs are combined. Consequently,digitalis levels should be monitored, and increased dose may be required. • Administer a single daily dose before breakfast each day to ensure consistent therapeutic levels. Theophylline clearance is decreased in hypothyroid states. to help prevent diffi- As the patient approaches normal thyroid function, theo- • Administer with a full glass of water culty swallowing. phylline dose may need to be adjusted frequently. • Monitor response carefully when beginning therapy to adjust dose according to patient response. • Monitor cardiac response to detect cardiac adverse effects. Prototype Summary: Levothyroxine • Assess patient carefully to detect any potential drug–drug Indications: Replacement therap y in hypothyroidism; pitu- interactions if giving thyroid hormone in combination with itary TSH suppression in the treatment of euthyroid goiters other drugs. and in the management of thyroid cancer; thyrotoxicosis in • Arrange for periodic blood tests of thyroid function to conjunction with other therapy; myxedema coma. monitor the effectiveness of the therapy. Actions: Increases the metabolic rate of body tissues,increas- • Provide thorough patient teaching, including drug name, ing oxygen consumption, respiration, and heart rate; the rate dosage and administration, measures to avoid adverse of fat, protein, and carbohydrate metabolism; and growth and effects, warning signs of problems, and the need for regular maturation evaluation if used for longer than recommended, to enhance patient knowledge of drug therapy and promote compliance. Pharmacokinetics: Route Onset Peak Duration Evaluation PO Slow 1–3 wk 1–3 wk • Monitor patient response to the drug (return of metabo- IV 6–8 h 24–48 h unknown lism to normal, prevention of goiter). T1/2: 6 to 7 days; metabolized in the liver and excreted in the • Monitor for adverse effects (tachycardia, hypertension, bile. anxiety, skin rash). Adverse effects: Tremors, headache, nervousness, palpitations, • Evaluate the effectiveness of the teaching plan (patient tachycardia, allergic skin reactions, loss of hair in the first f w can name drug, dosage, adverse effects to watch for, and months of therapy in children, diarrhea, nausea, vomiting. specific measures to avoid them). LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 571 Aptara

CHAPTER 37 Thyroid and Parathyroid Agents 571

CRITICAL THINKING SCENARIO Hypothyroidism

THE SITUATION that will be occurring to H.R. over the next week and H.R., a 38-year-old white woman, complains of “exhaus- beyond. The importance of taking the medication daily tion, lethargy, and sleepiness.” Her past history is sketchy, should be emphasized. The need to return for follow-up to her speech seems slurred, and her attention span is limited. evaluate the effectiveness of the medication and the effects Mr. R., her husband, reports feeling frustrated with H.R., on her body should also be stressed. Both H.R. and her hus- stating that she has become increasingly lethargic, disorga- band will need support and encouragement to deal with past nized, and uninvolved at home. He also notes that she has frustrations and the return to normal. Lifelong therapy will gained weight and lost interest in her appearance. Physical probably be needed, so further teaching will be important examination reveals the following remarkable findings once things have stabilized. pulse rate, 52/minute; blood pressure, 90/62 mm Hg; tem- perature, 96.8F (oral); pale, dry, and thick skin; periorbital NURSING CARE GUIDE FOR H.R.: edema; thick and asymmetric tongue; height, 5 ft 5 in; THYROID HORMONE weight, 165 lb. The immediate impression is that of Assessment: History and Examination hypothyroidism. Laboratory tests confirm this revealing ele- Review the patient’s history for allergies to any of these vated TSH and very low levels of triiodothyronine (T ) and 3 drugs, Addison disease, acute myocardial infarction not thyroxine (T ). Synthroid, 0.2 mg daily PO, is prescribed. 4 complicated by hypothyroidism, lactation, and thyrotoxicosis. CRITICAL THINKING Focus the physical examination on the following: What teaching plans should be developed for this patient? Neurological: orientation and affect What interventions would be appropriate in helping Mr. and Skin: color and lesions Mrs. R. accept the diagnosis and the pathophysiological CV: pulse, cardiac auscultation, blood pressure, and electro- basis for Mrs. R’s complaints and problems? cardiogram finding What body image changes will H.R. experience as her body Respiratory: respirations, adventitious sounds adjusts to the thyroid therapy? Hematological: thyroid function tests How can H.R. be helped to adjust to these changes and re- Nursing Diagnoses establish her body image and self-concept? Decreased Cardiac Output related to cardiac effects Imbalanced Nutrition: Less Than Body Requirements DISCUSSION related to effects on metabolism Hypothyroidism develops slowly. With it comes fatigue, Ineffective Tissue Perfusion related to thyroid effects lethargy, and lack of emotional affect—conditions that result Deficient Kn wledge regarding drug therapy in the patient’s losing interest in appearance, activities, and Implementation responsibilities. In this case, the patient’s husband, not Administer the drug once a day before breakfast with a full knowing that there was a physical reason for the problem, glass of water. became increasingly frustrated and even angry. Mr. R. Provide comfort, safety measures (e.g., temperature control, should be involved in the teaching program so that his feel- rest as needed, safety precautions). ings can be taken into consideration. Any teaching content Provide support and reassurance to deal with drug effects should be written down for later reference. (When H.R. and lifetime need. starts to return to normal, her attention span and interest Provide patient teaching regarding drug name, dosage, should return; anything that was missed or forgotten can be adverse effects, precautions, and warning signs to report. referred to in the written teaching program.) H.R. may be encouraged to bring a picture of herself Evaluation from a year or so ago to help her to understand and appreci- Evaluate drug effects: return of metabolism to normal; pre- ate the changes that have occurred. Many patients are totally vention of goiter. unaware of changes in their appearance and activity level Monitor for adverse effects: anxiety, tachycardia, hyperten- because the disease progresses so slowly and brings on sion, skin reaction. lethargy and lack of emotional affect. Monitor for drug–drug interactions as indicated for each drug. The teaching plan should include information about the Evaluate the effectiveness of the patient teaching program function of the thyroid gland and the anticipated changes and comfort and safety measures.

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572 PART 6 Drugs Acting on the Endocrine System

Hypothyroidism (continued)

PATIENT TEACHING FOR H.R. weight gain, sleeplessness, nervousness, unusual sweating, or intolerance to heat. • This hormone is designed to replace the thyroid hormone • Avoid taking any over-the-counter medication without firs that your body is not able to produce. The thyroid hormone checking with your health care provider because several of is responsible for regulating your body’s metabolism, or the these medications can interfere with the effectiveness of speed with which your body’s cells burn energy. Thyroid this drug. hormone actions affect many body systems, so it is very • Tell any doctor, nurse, or other health care provider important that you take this medication only as prescribed. involved in your care that you are taking this drug. You • Never stop taking this drug without consulting with your may also want to wear or carry medical identificatio health care provider. The drug is used to replace a very showing that you are taking this medication. This would important hormone and will probably have to be taken for alert any health care personnel taking care of you in an life. Stopping the medication can lead to serious problems. emergency to the fact that you are taking this drug. • Take this drug before breakfast each day with a full glass • While you are taking this drug, you will need regular med- of water. ical follow-up, including blood tests to check the activity • Thyroid hormone usually causes no adverse effects. You of your thyroid gland, to evaluate your response to the may notice a slight skin rash or hair loss in the first f w drug and any possible underlying problems. months of therapy. You should notice the signs and symp- • Keep this drug, and all medications, out of the reach of toms of your thyroid deficien y subsiding, and you will children. Do not give this medication to anyone else or feel “back to normal.” take any similar medication that has not been prescribed • Report any of the following to your health care provider: for you. chest pain, difficulty breathing sore throat, fever, chills,

Antithyroid Agents the radioactive iodine. Except during radiation emer gencies, the use of sodium iodide is reserv ed for those patients who Drugs used to block the production of thyroid hormone and are not candidates for sur gery, women who cannot become to treat hyperthyroidism include the thioamides and iodide pregnant, and elderly patients with such severe, complicating solutions (Table 37.2). Although these groups of drugs are not conditions that immediate thyroid destruction is needed. Iodine chemically related, they both block the formation of thyroid solutions include strong iodine solution, potassium iodide hormones within the thyroid gland (see Therapeutic Actions (Thyro-Block), and sodium iodide I131 (generic). See Table and Indications). 37.2 for usual indications for each drug.

Therapeutic Actions and Indications Pharmacokinetics The Thioamides Thioamides lower thyroid hormone levels by preventing the Thioamides formation of thyroid hormone in the thyroid cells,which low- These drugs are well absorbed from the GI tract and are then ers the serum levels of thyroid hormone. They also partially concentrated in the thyroid gland. The onset and duration of

inhibit the conversion of T4 to T3 at the cellular level. These PTU varies with each patient. Methimazole has an onset of drugs are indicated for the treatment of hyperthyroidism. action of 30 to 40 minutes and peaks in about 60 minutes. Thioamides include propylthiouracil (PTU) and methimazole Some excretion can be detected in the urine. Methimazole (Tapazole). crosses the placenta and is found in a high ratio in breast milk. PTU has a lo w potential for crossing the placenta and for Iodine Solutions entering breast milk (see Contraindications and Cautions). Low doses of iodine are needed in the body for the formation of thyroid hormone. High doses,however, block thyroid func- Iodine Solutions tion. Therefore, iodine preparations are sometimes used to These drugs are rapidly absorbed from the GI tract and widely treat hyperthyroidism but are not used as often as the y once distributed throughout the body fluids. Excretion occur were in the clinical setting (see Pharmacokinetics).The iodine through the urine. Strong iodine products, potassium iodide, solutions cause the thyroid cells to become o versaturated and sodium iodide are taken orally and have a rapid onset of with iodine and stop producing thyroid hormone. In some action, with ef fects seen within 24 hours and peak ef fects cases, the thyroid cells are actually destro yed. Radioactive seen in 10 to 15 days. The effects are short lived and may iodine (sodium iodide I 131) is taken up into the thyroid cells, even precipitate further thyroid enlargement and dysfunction which are then destro yed by the beta-radiation gi ven off by (see Adverse Ef fects). F or this reason, and because of the LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 573 Aptara

CHAPTER 37 Thyroid and Parathyroid Agents 573

availability of the more predictable thioamides, iodides are Clinically Important Drug–Drug Interactions not used as often as they once were in the clinical setting. The strong iodine products cross the placenta and are Thioamides known to enter breast milk, but the effects on the neonate are An increased risk for bleeding e xists when PTU is adminis- not known. Sodium iodide I131 enters breast milk and is rated tered with oral anticoagulants. Changes in serum le vels of pregnancy category X (see Contraindications and Cautions). theophylline, metoprolol, propranolol, and digitalis may lead to changes in the effects of PTU as the patient moves from the hyperthyroid to the euthyroid state. Contraindications and Cautions Antithyroid agents are contraindicated in the presence of any Iodine Solutions known allergy to antithyroid drugs to prevent hypersensitivity Because the use of drugs to destro y thyroid function moves reactions and during pregnancy because of the risk of adverse the patient from hyperthyroidism to hypothyroidism, patients effects on the fetus and the de velopment of cretinism. (If an who are taking drugs that are metabolized dif ferently in antithyroid drug is absolutely essential and the mother has hypothyroid and hyperthy roid states or dr ugs that ha ve a been informed about the risk of cretinism in the infant,PTU is small margin of safety that could be altered by the change in the drug of choice, but caution should still be used.) Another thyroid function should be monitored closely. These drugs method of feeding the baby should be chosen if an antithyroid include anticoagulants, theophylline, digoxin, metoprolol, drug is needed during lactation because of the risk of antithy- and propranolol. roid activity in the infant, including the de velopment of a neonatal goiter. (Again, if an antithyroid drug is needed,PTU is the drug of choice.) Use of strong iodine products is also contraindicated with Prototype Summary: Propylthiouracil pulmonary edema or pulmonary tuberculosis. Indications: Treatment of hyperthyroidism. Actions: Inhibits the synthesis of thyroid hormones, partially

inhibits the peripheral conversion of T4 to T3. Safe Medication Administration Pharmacokinetics: Name confusion has been reported between propylthiouracil Route Onset (PTU) and Purinethol (mercaptopurine), an antineoplastic PO Varies agent. Serious adverse effects could occur. Use extreme cau- tion when using these drugs. T1/2: 1 to 2 hours; metabolized in the liver and excreted in the urine. Adverse effects: Paresthesias, neuritis, vertigo, drowsiness, skin Adverse Effects rash, urticaria, skin pigmentation, nausea, vomiting, epigastric distress, nephritis, bone marrow suppression, arthralgia, myalgia, Thioamides edema. The adverse effects most commonly seen with thioamides are the ef fects of thyroid suppression: drowsiness, lethargy, bradycardia, nausea, skin rash, and so on. PTU is associated with nausea, vomiting, and GI complaints. GI effects are some- Prototype Summary: Strong Iodine Products what less pronounced with methimazole, so it may be the drug of choice for patients who are unable to tolerate PTU. Indications: Adjunct therap y for hyperthyroidism; thyroi d Methimazole is also associated with bone marrow suppression, blocking in a radiation emergency. so the patient using this drug must ha ve frequent blood tests Actions: Inhibit the synthesis of thyroid hormones and inhibit to monitor for this effect. the release of these hormones into the circulation. Iodine Solutions Pharmacokinetics: Route Onset Peak Duration The most common adverse effect of iodine solutions is hypothy- roidism; the patient will need to be started on replacement PO 24 h 10–15 d 6 wk thyroid hormone to maintain homeostasis. Other adverse effects T1/2: Unknown; metabolized in the li ver and excreted in the include iodism (metallic taste and burning in the mouth, sore urine. teeth and gums, diarrhea, cold symptoms, and stomach upset), Adverse effects: Rash, hypothyroidism, goiter, swelling of the staining of teeth, skin rash, and the development of goiter. salivary glands, iodism (metallic taste, burning mouth and Sodium iodide (radioacti ve I 131) is usually reserv ed for throat, sore teeth and gums, head cold symptoms, stomach use in patients who are older than 30 years of age because of upset, diarrhea), allergic reactions. the adverse effects associated with the radioactivity. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 574 Aptara

574 PART 6 Drugs Acting on the Endocrine System

Nursing Considerations for Patients KEY POINTS Receiving Antithyroid Agents ➧ Hypothyroidism, or lower-than-normal levels of thyroid hormone, is treated with replacement thyroid hormone. Assessment: History and Examination ➧ Hyperthyroidism, or higher-than-normal levels of thyroid • Assess for history of allergy to any antithyroid drug; hormone, is treated with thioamides, which block the pregnancy and lactation status; and pulmonary edema or thyroid from producing thyroid hormone, or with iodines, pulmonary tuberculosis if using strong iodine solutions, which prevent thyroid hormone production or destroy which could be cautions or contraindications to use of the parts of the gland. drug. • Assess for skin lesions; orientation and affect; baseline pulse, blood pressure, and ECG; respiration and adventi- THE PARATHYROID GLANDS tious sounds; and thyroid function tests, to determine baseline status before beginning therapy and for any poten- The parathyroid glands are four very small groups of glandular tial adverse effects. tissue located on the back of the thyroid gland (Figure 37.3). The parathyroid glands produce parathyroid hormone,an impor- tant regulator of serum calcium levels. Nursing Diagnoses Nursing diagnoses related to drug therapy might include the following: Structure and Function • Decreased Cardiac Output related to cardiac effects As mentioned earlier , the parafollicular cells of the thyroid • Imbalanced Nutrition: More Than Body Requirements gland produce the hormone calcitonin. Calcitonin responds related to changes in metabolism to high calcium le vels to cause lo wer serum calcium le vels • Risk for Injury related to bone marrow suppression and acts to balance the ef fects of the PTH, which works to • Deficient Knowledge regarding drug therapy elevate calcium levels. PTH is the most important re gulator of serum calcium levels in the body. PTH has many actions, including the following: Implementation With Rationale • Stimulation of osteoclasts or bone cells to release calcium • Administer propylthiouracil three times a day, around the from the bone clock, to ensure consistent therapeutic levels. • Increased intestinal absorption of calcium • Give iodine solution through a straw to decrease staining • Increased calcium resorption from the kidneys of teeth; tablets can be crushed. • Stimulation of cells in the kidney to produce calcitriol, the • Monitor response carefully and arrange for periodic blood active form of vitamin D, which stimulates intestinal tests to assess patient response and to monitor for adverse transport of calcium into the blood effects. • Monitor patients receiving iodine solution for any sign of iodism so the drug can be stopped immediately if such signs Control appear. Calcium is an electrolyte that is used in man y of the body’s • Provide thorough patient teaching, including measures to metabolic processes. These processes include membrane trans- avoid adverse effects, warning signs of problems, and the port systems, conduction of nerve impulses, muscle contrac- need for regular evaluation if used for longer than rec- tion, and blood clotting. To achieve all of these effects, serum ommended, to enhance patient knowledge of drug therapy levels of calcium must be maintainedbetween 9 and 11 mg/dL. and promote compliance. This is achieved through regulation of serum calcium by PTH and calcitonin (Figure 37.4). Evaluation The release of calcitonin is not controlled by the hypo- thalamic–pituitary axis but is regulated locally at the cellular • Monitor patient response to the drug (lowering of thyroid level. Calcitonin is released when serum calcium le vels rise. hormone levels). Calcitonin works to reduce calcium levels by blocking bone • Monitor for adverse effects (bradycardia, anxiety, blood resorption and enhancing bone formation. This action pulls dyscrasias, skin rash). calcium out of the serum for deposit into the bone. When • Evaluate the effectiveness of the teaching plan (patient serum calcium le vels are lo w, PTH release is stimulated. can name drug, dosage, adverse effects to watch for, and When serum calcium levels are high, PTH release is blocked. specific measures to avoid them). Another electrolyte—magnesium—also affects PTH • Monitor the effectiveness of comfort measures and com- secretion by mobilizing calcium and inhibiting the release of pliance to the regimen. PTH when concentrations rise abo ve or f all below normal. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 575 Aptara

CHAPTER 37 Thyroid and Parathyroid Agents 575

Increases calcium resorption Parathyroid glands

Parathormone

Increases calcium resorption Increases serum calcium

Calcitonin Inhibits calcium Parafollicular cells Biphosphonates resorption work here to increase calcium deposition in bones and decrease Calcitonin-human and serum calcium calcitonin-salmon work here to Reduces decrease serum serum ● FIGURE 37.3 Calcium control. calcium and inhibit calcium Parathormone and calcitonin work bone resorption to maintain calcium homeostasis in the body.

An increased serum phosphate le vel indirectly stimulates parathyroid activity. Renal tubular phosphate reabsorption is balanced by calcium secretion into the urine, which causes a drop in serum calcium, stimulating PTH secretion. The hor- mones PTH and calcitonin w ork together to maintain the delicate balance of serum calcium le vels in the body and to PTH ↓ + Calcitonin ↑ keep serum calcium levels within the normal range.

Serum Increase in kidney excretion calcium Reduction in GI absorption Parathyroid Dysfunction rises Reduction in bone resorption and Related Disorders Normal serum calcium Parathyroid dysfunction in volves either absence of PTH 4.5–5.8 mEq/L (hypoparathyroidism) or o verproduction of PTH (hyper- or 8.5–10.5 mg/dL parathyroidism). This dysfunction can af fect any age group. Box 37.1 e xplains the use of parathyroid agents across the Serum calcium Reduction in kidney excretion lifespan. falls Increase in GI absorption Increase in bone resorption Hypoparathyroidism The absence of PTH results in a low calcium level (hypocal- ↑ PTH cemia) and a relati vely rare condition called hypoparathy- roidism. This is most lik ely to occur with the accidental removal of the parathyroid glands during thyroid sur gery. ● FIGURE 37.4 Regulation of serum calcium. Parathyroid hormone Treatment consists in calcium and vitamin D therapy to increase (PTH) and calcitonin regulate normal serum calcium. As serum cal- cium rises, PTH is inhibited by calcitonin. The kidney then excretes serum calcium levels (see section on antihypocalcemic agents). more calcium, the GI system absorbs less, and a reduction in bone resorption occurs. As serum calcium falls, PTH is secreted and Hyperparathyroidism raises the calcium level by decreasing the amount of calcium lost in the kidney, increasing the amount absorbed in the GI tract and The e xcessive production of PTH leads to an ele vated increasing bone resorption. calcium le vel ( hypercalcemia) and a condition called LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 576 Aptara

576 PART 6 Drugs Acting on the Endocrine System

● TABLE 37.3 Signs and Symptoms of Calcium Imbalance

SYSTEM HYPOCALCEMIA HYPERCALCEMIA

Central nervous Hyperactive reflexes, paraesthesias, Lethargy, personality and behavior system positive Chvostek and Trousseau signs changes, polydipsia, stupor, coma Cardiovascular Hypotension, prolonged QT interval, Hypertension, shortening of the QT edema, and signs of cardiac insufficienc interval, atrioventricular block Gastrointestinal Abdominal spasms and cramps Anorexia, nausea, vomiting, constipation Muscular Tetany, skeletal muscle cramps, carpopedal Muscle weakness, muscle atrophy, spasm, laryngeal spasm, tetany ataxia, loss of muscle tone Renal Polyuria, flank pain, kidney stones, acute and/or chronic renal insufficienc Skeletal Bone pain, osteomalacia, bone Osteopenia, osteoporosis deformities, fractures

hyperparathyroidism. This can occur as a result of parathy- BOX 37.3 Treatments for Secondary roid tumor or certain genetic disorders. The patient presents Hyperparathyroidism with signs of high calcium levels (see Table 37.3). Primary hyperparathyroidism occurs more often in women between 60 In 2004, a new drug in a new class of calcimimetic agents, and 70 years of age. Secondary h yperparathyroidism occurs cinacalcet hydrochloride (Sensipar), was approved for treat- most frequently in patients with chronic renal failure (see Box ment of secondary hyperparathyroidism in patients undergoing 37.3 for more information). When plasma concentrations of dialysis for chronic kidney disease and for treatment of hyper- calcium are elevated secondary to high PTH levels, inorganic calcemia in patients with parathyroid carcinoma. Cinacalcet is a phosphate levels are usually decreased. Pseudorick ets (renal calcimimetic drug that increases the sensitivity of the calcium- sensing receptor to activation by extracellular calcium. In fibro ystic osteosis or renal rickets) may occur as a result of increasing the receptors’ sensitivity, cinacalcet lowers parathy- this phosphorus retention (hyperphosphatemia), which roid hormone (PTH) levels, causing a concomitant decrease in results from increased stimulation of the parathyroid glands serum calcium levels. and increased PTH secretion. The usual initial adult doses for secondary hyperparathy- The genetically linked disorder Paget disease is a condi- roidism are 30 mg/d PO, after which PTH, serum calcium, and tion of overactive osteoclasts that are eventually replaced by serum phosphorus levels are monitored to achieve the desired enlarged and softened bony structures. Patients with this dis- therapeutic effect. The usual dose range is 60 to 180 mg/d. The ease complain of deep bone pain,headaches, and hearing loss drug must be used in combination with vitamin D and/or phos- and usually have cardiac failure and bone malformation. phate binders. Postmenopausal osteoporosis can occur when dropping For parathyroid carcinoma, the initial dose is 30 mg PO levels of estrogen allow calcium to be pulled out of the bone, twice a day titrated every 2 to 4 weeks to maintain serum cal- cium levels within a normal range; 30 to 90 mg twice a day up resulting in a weak ened and hone ycombed bone structure. to 90 mg three to four times daily may be needed. Side effects Estrogen normally causes calcium deposits in the bone; that the patient may experience include nausea, vomiting, diar- osteoporosis is one of the man y complications that accom- rhea, and dizziness. pany the loss of estrogen at menopause (Box 37.4). Another treatment available for secondary hyperparathy- roidism related to renal failure is paricalcitol (Zemplar). KEY POINTS Paricalcitol is an analogue of vitamin D. Vitamin D levels are ➧ decreased in renal disease, leading to an increase in PTH Parathyroid glands produce PTH, which, together with levels and signs and symptoms of hyperparathyroidism. calcitonin, maintains the body’s calcium balance. Zemplar is taken orally or can be injected during hemodialysis. ➧ A low calcium level (hypocalcemia) is treated with vitamin The body recognizes the vitamin D and subsequently decreases D and calcium replacement therapy. the synthesis and storage of PTH, allowing a control over ➧ Hypercalcemia and hypercalcemic states are associated calcium levels. with postmenopausal osteoporosis, Paget disease, and The usual dose is 1 to 4 mcg PO from once a day to three malignancies. times a week, based on the patient’s calcium levels, or 0.04 to 0.1 mcg/kg injected during hemodialysis. The drug is rapidly absorbed with peak levels within 3 hours. The drug has a half- PARATHYROID AGENTS life of 12 to 20 hours. Patients will need regular serum calcium checks, and dose will be adjusted based on individual response. Adverse effects are usually mild, as long as the calcium levels The drugs used to treat disorders associated with parathyroid are monitored. Diarrhea, headache, and mild hypertension have function are drugs that af fect serum calcium levels. There is been reported. one parathyroid replacement hormone available and one form LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 577 Aptara

CHAPTER 37 Thyroid and Parathyroid Agents 577

paratide ( Forteo), a parathyroid hormone genetically engi- BOX 37.4 Gender Considerations neered from Escherichia coli bacteria using recombinant DNA technology. The drug was approved in 2002 to increase Osteoporosis bone mass in postmenopausal women and men with primary Osteoporosis is the most common bone disease found in or hypogonadal osteoporosis who are at high risk for fracture. adults. It results from a lack of bone-building cell (osteoclast) Additional hypocalcemic agents include calcitriol (Rocaltrol), activity and a decrease in bone matrix and mass, with less which is the most commonly used form of vitamin D, and calcium and phosphorus being deposited in the bone. This dihydrotachysterol (Hytakerol) (Table 37.4). can occur with advancing age, when the endocrine system is slowing down and the stimulation to build bone is absent; with menopause, when the calcium-depositing effects of Therapeutic Actions and Indications estrogen are lost; with malnutrition states, when vitamin C Vitamin D compounds regulate the absorption of calcium and and proteins essential for bone production are absent from the diet; and with a lack of physical stress on the bones from phosphate from the small intestine, mineral resorption in lack of activity, which promotes calcium removal and does bone, and reabsorption of phosphate from the renal tub ules. not stimulate osteoclast activity. The inactive, elderly, post- Working along with PTH and calcitonin to re gulate calcium menopausal woman with a poor diet is a prime candidate homeostasis, vitamin D actually functions as a hormone. for osteoporosis. Fractured hips and wrists, shrinking size, and With the once-daily administration, teriparatide stimulates curvature of the spine are all evidence of osteoporosis in this new bone formation, leading to an increase in sk eletal mass. age group. Besides the use of bisphosphonates to encour- It increases serum calcium and deceases serum phosphorus. age calcium deposition in the bone, several other interven- Use of these agents is indicated for the management of tions can help prevent severe osteoporosis in this group or in hypocalcemia in patients under going chronic renal dialysis any other people with similar risk factors. and for the treatment of hypoparathyroidism; teriparatide is • Aerobic exercise—Walking, even 10 minutes a day, has used for the treatment of postmenopausal or hypogonadal been shown to help increase osteoclast activity. En- osteoporosis (see Table 37.4). courage people to walk around the block or to park their car far from the door and walk. Exercise does not have to involve vigorous gym activity to be beneficial Pharmacokinetics • Proper diet—Calcium and proteins are essential for bone Calcitriol and dihydrotachysterol are well absorbed from the growth. The person who eats only pasta and avoids milk GI tract and widely distributed throughout the body. They are products could benefit from calcium supplements an encouragement to eat protein at least two or three times stored in the liver, fat, muscle, skin, and bones. Calcitriol has a week. Weight loss can also help to improve activity and a half-life of approximately 5 to 8 hours and a duration of decrease pressure on bones at rest. action of 3 to 5 days. Dihydrotachysterol has a shorter half- • Hormone replacement therapy (HRT)—For women, HRT life of 1 to 3 hours, and the duration of effect is less, usually has been very successful in decreasing the progression of 1 to 3 days. After being metabolized in the liver, they are pri- osteoporosis. Results of the Women’s Health Study showed marily excreted in the bile, with some found in the urine (see an increase in cardiovascular events with long-term HRT, Contraindications and Cautions for use of these drugs during making it a less desirable treatment. Women who are at pregnancy and lactation). high risk for breast cancer or who do not elect to take HRT Teriparatide is given by subcutaneous injection every day. may be good candidates for bisphosphonates. It is rapidly absorbed from the subcutaneous tissues,reaching The risk of osteoporosis should be taken into considera- peak concentration within 3 hours. The half-life of teri- tion as part of the health care regimen for all people as paratide is about 1 hour. Serum calcium levels will begin to they age. Prevention can save a great deal of pain and decline after about 6 hours and return to baseline 16 to 24 debilitation in the long run. hours after dosing. P arathyroid hormone is belie ved to be metabolized in the liver and excreted through the kidneys.

of calcitonin; the other drugs af fect calcium le vels in other Contraindications and Cautions ways. These drugs should not be used in the presence of any known Antihypocalcemic Agents allergy to any component of the drug, to avoid hypersensitivity reactions, or hypercalcemia or vitamin D toxicity, which would Deficient l vels of PTH result in hypocalcemia (calcium defi be exacerbated by these drugs. At therapeutic levels, these ciency). Vitamin D stimulates calcium absorption from the drugs should be used during pregnancy only if the benefit t intestine and restores the serum calcium to a normal le vel. the mother clearly outweighs the potential for adverse effects on Hypoparathyroidism is treated primarily with vitamin D and, the fetus. Calcitriol has been associated with hypercalcemia if necessary, dietary supplements of calcium. However, there (excessive calcium levels in the blood) in the baby when used is one parathyroid hormone available for therapeutic use,teri- by nursing mothers. Another method of feeding the baby LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 578 Aptara

578 PART 6 Drugs Acting on the Endocrine System

TABLE 37.4 DRUGS IN FOCUS Parathyroid Agents

Drug Name Usual Dosage Usual Indications

Antihypocalcemic agents

calcitriol (Rocaltrol) 0.5Ð2 mcg/d PO in the morning Management of hypocalcemia and reduction of parathormone levels dihydrotachysterol 0.8Ð2.4 mg/d PO initially, maintenance Management of hypocalcemia (Hytakerol) 0.2Ð1 mg/d PO based on serum calcium levels teriparatide (Forteo) 20 mg SQ daily Management of osteoporosis in postmenopausal women and men with primary hypogonadal osteoporosis who do not respond to standard therapy

Antihypercalcemic agents Bisphosphonates

alendronate 10 mg/d PO; for males and for Treatment of Paget disease, postmenopausal (Fosamax) postmenopausal osteoporosis, osteoporosis treatment and prevention, treatment of 70 mg PO every week or 10 mg/d PO for glucocorticoid-induced osteoporosis, osteoporosis in treatment, 35 mg PO every week or men 5 mg/d PO for prevention etidronate (Didronel) 5Ð10 mg/kg per day PO; 7.5 mg/kg per Treatment of Paget disease, postmenopausal day IV for 3 days for hypercalcemia of osteoporosis, hypercalcemia of malignancy, malignancy osteolytic bone lesions in cancer patients ibandronate (Boniva) 2.5 mg/d PO or 150 mg PO once per month Treatment of Paget disease; treatment and prevention on the same day each month of osteoporosis in postmenopausal women pamidronate (Aredia) 60Ð90 mg IV Treatment of Paget disease, postmenopausal osteoporosis in women, hypercalcemia of malignancy, osteolytic bone lesions in cancer patients risedronate (Actonel) 30 mg/d PO for 2 mo; reduce dose in renal Treatment of symptomatic Paget disease in patients dysfunction; 5 mg/d PO for osteoporosis who are at risk for complications; osteoporosis tiludronate (Skelid) 400 mg/d PO for 3 mo; reduce dose with Treatment of Paget disease that is not responsive to renal impairment other treatment zoledronic acid 4 mg IV as a single infusion over not less Treatment of Paget disease, postmenopausal (Zometa) than 15 min (given once a year for osteoporosis in women, hypercalcemia of malignancy, postmenopausal osteoporosis) osteolytic bone lesions in certain cancer patients

Calcitonins

calcitonin salmon Paget disease: 50Ð100 International Treatment of Paget disease, postmenopausal (Miacalcin) Units/d SQ or IM osteoporosis in conjunction with vitamin D and Postmenopausal osteoporosis: calcium supplements; emergency treatment of 100 International Units/d SQ or IM with hypercalcemia calcium and vitamin D Hypercalcemia: 4Ð8 International Units/kg SQ or IM q12h (Fortical) 200 International Units/d intranasally; Treatment of postmenopausal osteoporosis in alternate nostrils daily conjunction with calcium supplements and vitamin D

should be used if these drugs are needed during lactation. Patients should be informed of the risk of osteosarcoma. Caution should be used with a history of renal stones or dur- These patients should also tak e supplemental calcium and ing lactation, when high calcium levels could cause problems. vitamin D, increase weight-bearing exercise, and decrease Teriparatide is associated with osteosarcoma—a bone risk factors such as smoking and alcohol consumption. cancer—in animal studies, so its use is limited to post- menopausal women who have osteoporosis, are at high risk Adverse Effects for fractures, and are intolerant to standard therapies and to men with primary or hypogonadal osteoporosis who are at The adverse effects most commonly seen with these drugs high risk for fracture and are intolerant to standard therapies. are related to GI effects: metallic taste, nausea, vomiting, dry LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 579 Aptara

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mouth, constipation, and anorexia. CNS effects such as weak- Implementation With Rationale ness, headache, somnolence, and irritability may also occur . • Monitor serum calcium concentration before and periodi- These are possibly related to the changes in electrolytes that cally during treatment to allow for adjustment of dose to occur with these drugs. P atients with liver or renal dysfunc- maintain calcium levels within normal limits. tion may experience increased levels of the drugs and/or toxic • Provide supportive measures to help the patient deal with GI effects. and CNS effects of the drug (analgesics, small and frequent meals, help with activities of daily living). Clinically Important Drug–Drug Interactions • Arrange for a nutritional consultation if GI effects are The risk of hypermagnesemia increases if these drugs are taken severe to ensure nutritional balance. with magnesium-containing antacids. This combination should • Provide thorough patient teaching, including measures to be avoided. avoid adverse effects, warning signs of problems, and the Reduced absorption of these compounds may occur if they need for regular evaluation, to enhance the patient’s are taken with cholestyramine or mineral oil because they are knowledge about drug therapy and promote compliance. fat-soluble vitamins. If this combination is used, the drugs should be separated by at least 2 hours. Evaluation

Prototype Summary: Calcitriol • Monitor patient response to the drug (return of serum calcium levels to normal). Indications: Management of hypocalcemia in patients on • Monitor for adverse effects (weakness, headache, GI effects). chronic renal dialysis, management of hypocalcemia associated • Evaluate the effectiveness of the teaching plan (patient with hypoparathyroidism. can name drug, dosage, adverse effects to watch for, and Actions: A vitamin D compound that regulates the absorption specific measures to avoid them). of calcium and phosphate from the small intestine, mineral • Monitor the effectiveness of comfort measures and com- resorption in bone, and reabsorption of phosphate from the pliance with the regimen. renal tubules, increasing the serum calcium level. Pharmacokinetics: Route Onset Peak Duration Antihypercalcemic Agents PO Slow 4 h 3–5 d Drugs used to treat PTH excess or hypercalcemia include the bisphosphonates and calcitonin salmon. These drugs act on T1/2: 5 to 8 hours; metabolized in the liver and excreted in the bile. the serum levels of calcium and do not suppress the parathy- roid gland or PTH (see Table 37.4). Adverse effects: Weakness, headache, nausea, vomiting, dry mouth, constipation, muscle pain, bone pain, metallic taste. Therapeutic Actions and Indications Nursing Considerations for Patients Bisphosphonates Receiving Antihypocalcemic Agents The bisphosphonates act to slow or block bone resorption; by Assessment: History and Examination doing this, they help to lower serum calcium levels, but they do not inhibit normal bone formation and mineralization. • Assess for history of allergy to any component of the Bisphosphonates include etidronate ( Didronel), ibandronate drugs, hypercalcemia, vitamin toxicity, renal stone, and (Boniva), pamidronate (Aredia), risedronate (Actonel), tilu- pregnancy or lactation, which could be cautions or con- dronate (Skelid), alendronate (Fosamax), and zoledronic acid traindications to use of the drug. (Zometa). These drugs are used in the treatment of Paget dis- • Assess for the presence of any skin lesions; orientation ease and of postmenopausal osteoporosis in w omen, and and affect; liver evaluation; serum calcium, magnesium, alendronate is also used to treat osteoporosis in men. See and alkaline phosphate levels; and radiographs of bones Table 37.4 for usual indications for each drug. as appropriate, to determine baseline status before begin- ning therapy and any potential adverse effects. Calcitonins Nursing Diagnoses The calcitonins are hormones secreted by the thyroid gland to balance the ef fects of PTH. Currently the only calcitonin Nursing diagnoses related to drug therapy might include the readily available is calcitonin salmon ( Fortical, Miacalcin). following: These hormones inhibit bone resorption, lower serum cal- • Acute Pain related to GI or CNS effects cium levels in children and in patients with Paget disease,and • Imbalanced Nutrition: Less Than Body Requirements increase the e xcretion of phosphate, calcium, and sodium related to GI effects from the kidney. See Table 37.4 for usual indications for each • Deficient Knowledge regarding drug therapy drug. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 580 Aptara

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Pharmacokinetics They should not be used during lactation because the calcium-lowering effects could cause problems for the baby. Bisphosphonates Calcitonin salmon should not be used with a known allergy to These drugs are well absorbed from the small intestine and do salmon or fish products. These drugs should be used with not undergo metabolism. They are excreted relatively unchanged caution in patients with renal dysfunction or pernicious ane- in the urine. The onset of action is slo w, and the duration of mia, which could be exacerbated by these drugs. action is days to weeks. Patients with renal dysfunction may experience toxic le vels of the drug and should be e valuated for a dose reduction. See Contraindications and Cautions for Adverse Effects use of these drugs during pregnancy and lactation. Bisphosphonates Calcitonins The most common adverse effects seen with bisphosphonates These drugs are metabolized in the body tissues to inacti ve are headache, nausea, and diarrhea. There is also an increase fragments, which are e xcreted by the kidne y. Calcitonins in bone pain in patients with P aget disease, but this ef fect cross the placenta and ha ve been associated with adv erse usually passes after a fe w days to a fe w weeks. Esophageal effects on the fetus in animal studies. These drugs inhibit lac- erosion has been associated with alendronate, ibandronate, tation in animals; it is not known whether they are excreted in and risedronate if the patient has not remained upright for at breast milk (see Contraindications and Cautions). Salmon least 30 minutes after taking the tablets. calcitonin can be gi ven by injection or by nasal spray . By Calcitonins either route, peak effects are seen within 40 minutes, and the duration of effect is 8 to 24 hours. The most common adverse effects seen with these drugs are flushing of the ace and hands, skin rash, nausea and vomit- Contraindications and Cautions ing, urinary frequency, and local inflammation at the site o injection. Man y of these side ef fects lessen with time, the Bisphosphonates time varying with each individual patient. These drugs should not be used in the presence of hypocal- cemia, which could be made worse by lowering calcium lev- Clinically Important Drug–Drug Interactions els, or with a history of an y allergy to bisphosphonates to avoid hyper sensitivity r eactions. Fetal abnormalities ha ve Bisphosphonates been associated with these drugs in animal trials, and they Oral absorption of bisphosphonates is decreased if the y are should not be used during pregnancy unless the benefit to th taken concurrently with antacids, calcium products, iron, or mother clearly outweighs the potential risk to the fetus or multiple vitamins. If these drugs need to be tak en, they neonate. Extreme caution should be used when nursing should be separated by at least 30 minutes. because of the potential for adverse effects on the baby. GI distress may increase if bisphosphonates are combined Alendronate should not be used by nursing mothers. Caution with aspirin; this combination should be avoided if possible. should be used in patients with renal dysfunction, which could interfere with excretion of the drug, or with upper GI Calcitonins disease, which could be aggravated by the drug. There are have been no clinically important drug–drug inter- Alendronate, ibandronate, and risedronate need to be actions reported with the use of calcitonins. taken on arising in the morning, with a full glass of water, fully 30 minutes before an y other food or be verage, and the patient must then remain upright for at least 30 minutes; tak- Prototype Summary: Alendronate ing the drug with a full glass of water and remaining upright Indications: Treatment and prevention of osteoporosis in post- for at least 30 minutes facilitates delivery of the drug to the menopausal women and in men; treatment of glucocorticoid- stomach. These drugs should not be gi ven to anyone who is induced osteoporosis; treatment of Paget disease in certain unable to remain upright for 30 minutes after taking the drug patients. because serious esophageal erosion can occur. Actions: Slows normal and abnormal bone resorption without Zoledronic acid should be used cautiously in aspirin- inhibiting bone formation and mineralization. sensitive asthmatic patients. Alendronate and risedronate are now available in a once-a-week formulation to decrease the Pharmacokinetics: number of times the patient must take the drug, which should Route Onset Duration increase compliance with the drug re gimen. Ibandronate is PO Slow Days available in a once-a-month formulation. T1/2: Greater than 10 days; not metabolized, but excreted in Calcitonins the urine. Adverse effects: Headache, nausea, diarrhea, increased or recur- These drugs should be used in pregnancy only if the benefit t rent bone pain, esophageal erosion. the mother clearly outweighs the potential risk to the fetus. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 581 Aptara

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Prototype Summary: Calcitonin Salmon • Assess the patient carefully for any potential drug–drug interactions if giving in combination with other drugs to Indications: Paget disease, postmenopausal osteoporosis, prevent serious effects. emergency treatment of hypercalcemia. • Arrange for periodic blood tests of renal function if using Actions: Inhibits bone resorption; lowers elevated serum cal- gallium to monitor for renal dysfunction. cium in children and patients with P aget disease; increases • Provide comfort measures and analgesics to relieve bone the excretion of filtered phosphate calcium, and sodium by pain if it returns as treatment begins. the kidney. • Provide thorough patient teaching, including measures to Pharmacokinetics: avoid adverse effects, warning signs of problems, the Route Onset Peak Duration need for regular evaluation if used for longer than rec- IM, SQ 15 min 3–4 h 8–24 h ommended, and proper administration of nasal spray, to Nasal Rapid 31–39 min 8–24 h enhance patient knowledge about drug therapy and promote compliance. T1/2: 1.43 hours; metabolized in the kidne ys and excreted in urine. Adverse effects: Flushing of f ace and hands, nausea, vomit- Evaluation ing, local inflammatory reactions at injection site, nasal irri- • Monitor patient response to the drug (return of calcium tation if nasal form is used. levels to normal; prevention of complications of osteo- porosis; control of Paget disease). • Monitor for adverse effects (skin rash; nausea and vomit- ing; hypocalcemia; renal dysfunction). Nursing Considerations for Patients • Evaluate the effectiveness of the teaching plan (patient Receiving Antihypercalcemic Agents can name drug, dosage, adverse effects to watch for, and specific measures to avoid them). Assessment: History and Examination • Monitor the effectiveness of comfort measures and com- • Assess for history of allergy to any of these products or to pliance with the regimen. fish products with salmon calcitonin to avoid hypersensi- tivity reaction; pregnancy or lactation; hypocalcemia; and KEY POINTS renal dysfunction, which could be cautions or contraindica- tions to use of the drug. ➧ The parathyroid glands are located behind the thyroid • Assess for the presence of any skin lesions; orientation gland and produce PTH, which works with calcitonin, and affect; abdominal examination; serum electrolytes; produced by thyroid cells, to maintain the calcium bal- and renal function tests, to determine baseline status before ance in the body. beginning therapy and for any potential adverse effects. ➧ Hypocalcemia, or low levels of calcium, is treated with vitamin D products and calcium replacement therapy. Nursing Diagnoses ➧ Hypercalcemia can occur in postmenopausal osteoporosis and Paget disease, as well as related to malignancy. Nursing diagnoses related to drug therapy might include ➧ Hypercalcemia is treated with bisphosphonates, which the following: slow or block bone resorption to lower serum calcium • Acute Pain related to GI or skin effects levels, or calcitonin, which inhibits bone resorption, low- • Imbalanced Nutrition: Less Than Body Requirements ers serum calcium levels in children and patients with related to GI effects Paget disease, and increases the excretion of phosphate, • Anxiety related to the need for parenteral injections (spe- calcium, and sodium from the kidney. cific drugs) • Deficient Knowledge regarding drug therapy CHAPTER SUMMARY Implementation With Rationale • The thyroid gland uses iodine to produce thyroid hor- • Ensure adequate hydration with any of these agents to mones. Thyroid hormones control the rate at which most reduce the risk of renal complications. body cells use energy (metabolism). • Arrange for concomitant vitamin D, calcium supplements, • Control of the thyroid gland is an intricate among between and hormone replacement therapy if used to treat post- TRH, released by the hypothalamus; TSH, released by the menopausal osteoporosis. anterior pituitary; and circulating levels of thyroid hormone. • Rotate injection sites and monitor for inflammation if • Hypothyroidism, or lower-than-normal levels of thyroid using calcitonins to prevent tissue breakdown and irritation. hormone, is treated with replacement thyroid hormone. • Monitor serum calcium regularly to allow for dose adjust- • Hyperthyroidism, or higher-than-normal levels of thyroid ment as needed. hormone, is treated with thioamides, which block the LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 582 Aptara

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thyroid from producing thyroid hormone, or with iodines, which prevent thyroid hormone production or destroy WEB LINKS parts of the gland. • The parathyroid glands are located behind the thyroid gland Patients, health care providers, and students may want to and produce PTH, which works with calcitonin, produced by consult the following Internet sources: thyroid cells, to maintain the calcium balance in the body. http://www.the-thyroid-society.org • Hypocalcemia, or low levels of calcium, is treated with Information on thyroid diseases, support groups, treatments, vitamin D products and calcium replacement therapy. and research. • Hypercalcemia and hypercalcemic states include post- http://www.endo-society.org menopausal osteoporosis and Paget disease, as well as Information on endocrine diseases, screening, and treatment. hypercalcemia related to malignancy. • Hypercalcemia is treated with bisphosphonates or calcitonin. http://www.nof.org Bisphosphonates slow or block bone resorption, which Information on osteoporosis—support groups, screening, lowers serum calcium levels. Calcitonin inhibits bone treatment, and research. resorption, lowers serum calcium levels in children and http://www.osteorec.com patients with Paget disease, and increases the excretion of Information on national and international research on osteo- phosphate, calcium, and sodium from the kidney. porosis and related bone diseases.

CHECK YOUR UNDERSTANDING

Answers to the questions in this chapter can be found in c. Graves disease. Answers to Check Your Understanding Questions on the d. acute thyrotoxicosis. CD-Rom in the front of the book. 5. Assessing a patient’s knowledge of his or her thyroid replacement therapy would show good understanding if MULTIPLE CHOICE the patient stated: Select the best answer to the following. a. “My wife may use some of my drug, since she wants to lose weight.” 1. The thyroid gland produces the thyroid hormones T3 b. “I should only need this drug for about 3 months.” and T4, which are dependent on the availability of c. “I can stop taking this drug as soon as I feel like my a. iodine produced in the liver. old self.” b. iodine found in the diet. d. “I should call if I experience unusual sweating, c. iron absorbed from the gastrointestinal tract. weight gain, or chills and fever.” d. parathyroid hormone to promote iodine binding. 6. Administration of propylthiouracil (PTU) would include 2. The thyroid gland is dependent on the giving the drug hypothalamic–pituitary axis for regulation. Increasing a. once a day in the morning. the levels of thyroid hormone (by taking replacement b. around the clock to assure therapeutic levels. thyroid hormone) would c. once a day at bedtime to decrease adverse effects. a. increase hypothalamic release of TRH. d. if the patient is experiencing slow heart rate, skin b. increase pituitary release of TSH. rash, or excessive bleeding. c. suppress hypothalamic release of TRH. 7. The parathyroid glands produce PTH, which is impor- d. stimulate the thyroid gland to produce more T3 and T4. tant in the body as 3. Goiter, or enlargement of the thyroid gland, is usually a. a modulator of thyroid hormone. associated with b. a regulator of potassium. a. hypothyroidism. c. a regulator of calcium. b. iodine deficiency. d. an activator of vitamin D. c. hyperthyroidism. d. underactive thyroid tissue. 8. A drug of choice for the treatment of postmenopausal osteoporosis would be 4. Thyroid replacement therapy is indicated for the treat- a. risedronate. ment of b. alendronate. a. obesity. c. tiludronate. b. myxedema. d. calcitriol. LWBK374_c37_p563-583.qxd 28/08/2009 08:35 AM Page 583 Aptara

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MULTIPLE RESPONSE d. to stay upright for at least 1/2 hour after taking the drug. Select all that apply. e. to take the drug with meals to avoid GI upset. 1. A patient who is receiving a bisphosphonate for the f. to avoid exercise to prevent bone fractures. treatment of postmenopausal osteoporosis should be 2. Hypothyroidism is a very common and often missed dis- taught order. Signs and symptoms of hypothyroidism include a. to also take vitamin D, calcium, and hormone a. increased body temperature. replacement. b. thickening of the tongue. b. to restrict fluids as much as possible. c. bradycardia. c. to take the drug before any food for the day, with a d. loss of hair. full glass of water. e. excessive weight loss. f. oily skin.

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