CHAPTER 7 Overview of the Endocrine System and Agents Sherrill J. Brown, DVM, PharmD, BCPS | Kendra Keeley Procacci, PharmD, BCPS, AE–C | Katherine S. Hale, PharmD, BCPS LEARNING OBJECTIVES KEY TERMS AND DEFINITIONS After completing this chapter, you should be able to Acromegaly — overproduction of growth hormone. 1. Describe the negative feedback system used to regulate levels of many of the body’s Feedback system — method of hormones regulation of hormone levels where the 2. Defi ne the following: target hormone affects the production of the stimulating hormone, either PART ● Acromegaly negatively (inhibits production) or ● Hyperparathyroidism positively (stimulates production). 3 ● Hyperthyroidism Hyperparathyroidism — ● Hypoparathyroidism overactive parathyroid glands, ● Hypopituitarism classifi ed as primary, secondary, or tertiary depending on cause of ● Hypothyroidism parathyroid hyperactivity and the 3. State the brand and generic names of the most widely prescribed medications for presence of hyper- or hypocalcemia. pituitary disorders, thyroid disorders, and parathyroid disorders Hypoparathyroidism — a 4. Be familiar with their routes of administration and dosage forms, and the most disorder related to inadequate secretion of parathyroid hormone by common adverse effects of medications used to treat pituitary disorders, thyroid the parathyroid glands resulting in disorders, and parathyroid disorders abnormally low levels of calcium in 5. Describe the therapeutic effects of medications used to treat pituitary disorders, the blood. thyroid disorders, and parathyroid disorders Hypopituitarism — defi ciency of pituitary hormones. Hypothyroidism — a condition which the body does not produce he endocrine system consists of glands located throughout the body, which enough thyroid hormone. T release hormones into the blood. Hormones are chemicals released from Osteomalacia — bone disease one cell in the body that affect other cells in other parts of the body. Endocrine characterized by softening of the 1,2 bones due to inadequate deposits of hormones are released or secreted directly into the bloodstream. calcium and vitamin D. The release of many hormones is regulated by a feedback system . Positive Primary hyperparathyroidism (PHPT) — a disorder resulting from feedback in the form of low levels of the target hormone results in an increase one or more overactive parathyroid in the release of the stimulating pathway. Negative feedback in the form of high glands, resulting in high levels of levels of the target hormone decreases the release of the stimulating pathway. calcium in the blood. For example, the hypothalamus produces thyrotropin-releasing hormone (TRH), Pseudohypoparathyroidism (PHP) — a collection of disorders which stimulates the production and secretion of thyroid-stimulating hormone resulting from genetic mutations (TSH) by the pituitary gland. TSH then signals the thyroid gland to produce where patients exhibit clinical thyroid hormones. The presence of thyroid hormones in the blood provides symptoms of hypoparathyroidism, but are resistant to the actions negative feedback, which inhibits the production and secretion of more TRH by of parathyroid hormone versus the hypothalamus. This negative feedback insures that thyroid hormones do not inadequate secretion. exceed normal levels and cause toxic effects (Figure 7-1). 551360_Ch07_p127-152.indd1360_Ch07_p127-152.indd 112929 99/28/12/28/12 33:22:22 PPMM CHAPTER 7 | Overview of the Endocrine System and Agents 130 Renal osteodystrophy— bone disease characterized by defective bone development and softening of the bones due to chronic kidney disease. Secondary hyperparathyroidism (SHPT) — a disorder resulting from chronic, long-term states of hypocalcemia and resistance to the actions of parathyroid hormone; the parathyroid glands become overactive and the glands become enlarged. Serum — the clear fl uid obtained from blood when it has been separated into its solid and liquid components after clotting has occurred. Tertiary hyperparathyroidism (THPT) — severe secondary hyperparathyroidism despite efforts to correct the condition; patients are in a chronic state of hypercalcemia due to constant overproduction of Figure 7-1. Example of feedback system for hormone regulation. parathyroid hormone. Trophic hormones — hormones released by the pituitary gland that Pituitary Gland regulate other endocrine glands. CASE STUDY Traumatic hypopituitarism Amy Bird is a 47-year-old female who fractured her skull in an automobile accident 10 months ago. She was unconscious for 4 days but appeared to recover completely from her injuries. Since the accident, Ms. Bird has lost weight, becomes dizzy when she stands up, and says that she is tired “all the time.” Her doctor told her that the blood supply to her pituitary gland was damaged in the accident and that she would need to take several different medications to treat this problem. Overview of Pituitary Gland The pituitary gland is located in the brain and consists of two lobes: the anterior lobe and the posterior lobe (Figure 7-2). Most hormones released from the pituitary gland regulate other endocrine glands and are called trophic hormones . The trophic hormones secreted by the anterior pituitary gland are listed below: ● Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) control the production of sex hormones by the ovaries and testicles. ● Corticotropin, also called adrenocorticotropic hormone or ACTH, acts on the adrenal gland (the adrenal gland is covered in more detail in Chapter 8). ● Thyroid-stimulating hormone (TSH) stimulates the production of thyroid hormones. Nontrophic hormones produced by the anterior pituitary gland are growth hormone (GH) and prolactin. GH induces growth in children, and prolactin stimulates milk 551360_Ch07_p127-152.indd1360_Ch07_p127-152.indd 113030 77/18/12/18/12 66:43:43 AAMM.