Odisha Review December - 2012

Endocrine System With Special Reference to

Soma Mishra

Endocrine system consisting of a group of ductless viz. pituitary, thyroid, parathyroid, pineal, , , , adrenal etc. plays a very vital role in governing human behavior. Thyroid is one of the most important glands that control body’s and calcium level. It secretes iodothyronines that are (tri-iodo- thyronine, thyroxine) and . Its is mainly regulated by TRH (thyrotropin releasing ) and TSH (thyroid stimulating hormone). It helps in growth (physical, sexual, mental) – development- and calorigenesis- metabolism. The status of thyroid gland may be Euthyroid or Hypothyroid or Hyperthyroid. includes cretinism in children and myxoedema in adults. Common causes of hyperthyroid state are Grave’s disease, multinodular goiter, , etc. Any enlargement of thyroid gland, regardless of cause, is called goiter. Some common investigations for Introduction thyroid diseases are estimation of serum T3, T4 The endocrine system or hormonal system and TSH, , radioiodine uptake, thyroid is a complex system composed of a group of imaging, etc. Common drug used in ductless glands known as endocrine glands that hypothyroidism is eltroxin, is pour their i.e. directly into and supplementation in goiter. for passage to different body organs known This paper presents a full picture of thyroid gland, as target organs in order to control their its functioning, disorders, and treatments which is functioning, metabolism, cell permeability, growth, very significant for human survival. differentiation and stress conditions.

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The endocrine system includes the Diseases of the endocrine system result , thyroid gland, parathyroid glands, from too much or too little hormone secretion or , pancreas, and testes. The from the inability of the body to utilize a hormone thymus, , certain portions of the effectively. , the , and are also considered endocrine organs. Lack of any one of the hormones produced by these glands causes serious disorders, many of them are now produced synthetically and used in treatment where a deficiency exists. The regulation of body functions by the endocrine system depends on the existence of specific receptor cells in target organs that respond in specialized ways to the minute quantities of the hormonal messengers. The amounts of hormones are maintained by feedback mechanisms that depend on interactions between the endocrine glands, the blood levels of the various hormones, and activities of the target . Pituitary control The pituitary gland otherwise known as Thyroid Gland: the master gland regulates many of the other endocrine glands. It is located at the base of the Origin: It is endodermal in origin and in human , nestled in a bony structure called the embryo, it develops from the primitive fore gut. sellaturcica. It is also called the hypophysis. It History: the thyroid was first identified by the controls the adrenal gland, the sex hormones and anatomist Thomas Wharton in 1656. Thyroid the thyroid gland. hormone was only identified in the 19th century. Other endocrine glands Position: it is located in front part of the The other endocrine glands are not and upper part of in the region. directly controlled by the pituitary like the Structure: it is the longest with parathyroid glands, the endocrine portion of the weight of about 25 grams. However, is influenced pancreas, the thymus, the kidney and the pineal by age, sex, reproductive state and diet of the gland. person. It is bi-lobed in human beings. It is ‘H’- The endocrine system serves an essential shaped having two fairly symmetrical lateral lobes integrative function. Humans are beset by the lying on each side of the otherwise variety of insults, such as trauma, infection, tumor known as Adam’s apple, each about 5x2x2 cm formation, genetic defects and emotional damage. connected by a narrow band of tissue called isthmus. It forms a crossing in front of 2nd, 3rd and The endocrine gland plays a key role in responding th to these stressful stimuli. 4 tracheal rings. Gland is highly vascular,

55 Odisha Review December - 2012 composed of approximately 3 million rounded released from thyroid is T4 but ultimately an follicles arranged in lobules each lobule having called removes one iodine about 40 follicles and held together by connective atom from T4 and produce T3. tissue. Regulation of Hormone Secretion: Follicle wall is lined by cuboidal The major regulators of T3, T4 secretions and encloses hormone rich colloid secreted by are TSH, TRH, feedback, auto regulation, the epithelium. Under the stimulation of thyroid exposure to cold and (of stimulating hormone, low cuboidal epithelium is ). Hypothalamus secretes TRH converted into a tall columnar epithelium. (Thyrotropin Releasing Hormone) which Blood flow in thyroid gland is about 3.5 stimulates TSH secretion of the to 6.0 ml/gm/minute. Sympathetic fibers from the that finally leads to secretion of T3 and T4. superior, middle and inferior cervical ganglia and Elevated levels of serum T3 and T4 inhibits the parasympathetic fibers from superior and primarily the thyrotropes of anterior pituitary and inferior recurrent laryngeal branches of vagus only to little extent the hypothalamus. Daily iodine cranial supply thyroid gland. requirement for proper functioning of thyroid is Hormones: 200 micrograms. If contains excess iodine, the iodine trapping mechanism becomes inefficient Hormones released from thyroid gland are, so that not much of iodine is trapped, whereas if 1. Thyroxine or T4 food iodine uptake is very low, the iodine trapping 2. or T3 mechanism becomes super efficient so that the entire amount of available iodine is trapped by 3. Calcitonin follicular cells. Cold stimulates production of TRH Except these three hormones there is and serum T3, T4 is increased and somatostatin another hormone Reversed T3 or RT3 which is of hypothalamus inhibits thyroid secretion. biologically inert. T3, T4 are iodinated derivatives Role of Iodothyronines: of amino acid secreted by the follicles. Calcitonin is non-iodinated hormone secreted by The thyroid plays an important role in parafollicular cells or C-cells. Thyroid gland is regulating the body’s metabolism and calcium stimulated to secrete hormones by TSH or balance. thyrotropin from the anterior lobe of pituitary — T3 increases . On the gland. other hand, T3 increases peripheral Biochemistry: utilization of due to T3 induced calorigenesis. On the whole in The are modifications, called hyperthyroidism, blood sugar level thyronines, of an amino acid, tyrosine. Thyroid increases. But according to some recent hormones are heavily laden with iodine. The major findings, in hyperthyroidism, resistance of active thyroid hormones are thyroxine(T4) and target cells to rises. triiodothyronine(T3). Thyroxine and T3 are formed by the molecular addition of iodine to the — T3 decreases serum cholesterol level. amino acid tyrosine while the later is bound to the Also the free level is raised by . Most of the iodothyronine thyroid hormones.

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— T3 enhances both (synthesis) Diseases Related to Thyroid Gland: and catabolism (breaking down) of The state of normal thyroid function is protein. However, under physiological called Euthyroidism. Diseases of the thyroid gland condition anabolism supervenes. result from too much or too little secretion of — T3 causes loss of calcium via urine. thyroid hormones. can develop in Hypothyroidism: hyperthyroidism. It is the condition in which the thyroid is — Thyroxine controls the BMR (Basal underactive. It is producing an insufficient amount Metabolic Rate) by regulating oxidation of thyroid hormones. It is the most common and production of energy. thyroid disorder in which the body’s metabolism became slow. — It regulates urine output by controlling the working of the kidney. Causes of Hypothyroidism: — It maintains the muscular and nervous On the basis of cause hypothyroidism can toning. be classified under two groups- — Physical as well as mental growth is (a) Primary hypothyroidism and (b) Secondary hypothyroidism regulated by thyroxine. In primary hypothyroidism, fault is — It is must for the development of skeletal primarily in the thyroid gland, for some reasons, system. thyroid is failing to produce adequate amount of It is required for tissue differentiation as iodothyronines. It can be due to (1) iodine well as metamorphosis in . deficiency in the food or in maternal blood (for the ), (2) destruction of thyroid due to surgical It is must for reproduction. removal, radioiodine , Hashimoto’s disease Role of Calcitonin or Thyrocalitonin: (in which the body produces antibodies against the thyroid gland). Secondary hypothyroidism fault It is a hormone, released from lies in the pituitary or the hypothalamus, poor extrafollicular or parafollicular cells of thyroid amounts of TSH or TRH secretion is the cause. gland. It is non-iodinated thyroid hormone, which Secondary hypothyroidism is rare. checks the concentration of calcium and phosphate in blood plasma by decreasing Types of Hypothyroidism: mobilization from . Bones, therefore, remain Hypothyroidism is classified according to strong and solid. It also checks absorption of the age of onset. Thus (1) when the calcium and phosphate from gastrointestinal tract hypothyroidism is present since birth the condition and increases excretion of calcium and phosphate. is called cretinism but (2) when appears after the It is under the feedback control of plasma calcium attainment of adulthood; it is adult hypothyroidism, concentration and is secreted when concentration myxoedema or Gull’s disease. of calcium rises in the blood. Calcitonin is (1) Cretinism antagonistic to parathormones secreted by Also called congenital myxoedema or . It is hypocalcemic and cretinoid dysplasia, is a disease of infants, which hypophosphatemic. does not appear until the age of six months

57 Odisha Review December - 2012 because till that age, mother’s milk provides Graves’ disease or Exopthalmic Goiter: enough iodine. It is due to enlargement of thyroid gland It is characterized by dwarfism, physical and oversecretion of thyroxine probably due to and mental deficiencies or under development with an antibody which stimulates the thyroid too much a peculiar infantile facial expression, big nose, in turn causing the excess production of thyroid scanty hair, low body temperature, low beat, hormone. It is characterized by bulging of eyes low blood pressure, large head, thick legs, pot (i.e. exopthalmia), high BMR, increased oxidation belly, pigeon chest, protruding , swollen of food, emaciation, increased heartbeat, higher eyelids, short neck, dry , deformed bones and body temperature, excessive sweating, teeth and uncoordinated gait, retarded sexual restlessness, nervousness, dizziness, little sleep development, which includes delayed and fine tremors in stretched hands. Graves’ development of sex glands, sex organs and secondary sexual characters. If it is treated early disease is categorized as an autoimmune disorder. with thyroid hormones and trace iodine The disease is most common in young to middle- supplementation of the diet, significant aged women and tends to run in families. It can improvement can be seen. be rectified by removal of inflamed part of thyroid gland. (2) Myxoedema (Gull’s Disease) Hyperthyroidism caused by multinodular It is a disease of adults which is 7-8 times goiter in which one or more nodules of the thyroid more common in females than in males. It is become over active. The over active nodules characterized by puffy appearance due to actually act as benign thyroid tumors. Another subcutaneous accumulation of hyaluronic acid – cause is thyroiditis but it causes temporary protein – chondroitin sulphate complex which attracts water and leads to edema, low basal hyperthyroidism, usually followed with metabolism, retarded oxidation, lack of alertness, hypothyroidism. It is an of the thyroid intelligence, failure to take initiative, retarded gland. In addition, if a person takes too many sexual power, high blood cholesterol level. There thyroid hormone tablets, hyperthyroidism may is swelling of tongue and larynx causing occur. hoarseness and slow and slurring speech, hair Treatment of Thyroid Disorders: fallout from axilla, pubis, head and eyebrows. It can be treated with oral administration of thyroid The goal of treatment for any disorder is hormones. to restore the thyroid gland to normal function, producing normal levels of thyroid hormones. Hyperthyroidism: Specific treatment for any thyroid disorder will Hyperthyroidism means over activity of be determined by the physician based on:- the thyroid gland, resulting in too much of thyroid — Patient’s overall health and medical hormones in the bloodstream. The oversecretion history of thyroid hormones leads to over activity of the body’s metabolism. — Extent of the disease Causes of Hyperthyroidism: — Patient’s tolerance for specific medications, procedures, or Graves’ disease is the most common cause of hyperthyroidism. — Expectations for the course of the disease

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— Patient’s opinion or preference d) Toxic goiter: - Enlargement of thyroid gland Treatment for Hypothyroidism: due to some toxic material and also associated with exopthalmic and systemic disease. Very high Treatment may include prescription of concentration of iodine may also cause thyroid hormones to replace the deficient hypothyroidism by inhibiting iodine organification. hormones. Dosage of thyroid hormone may need It is known as Wolff-Chaikoff Effect. Such goiter to be increased over the years. Yearly or biyearly is called Hokkihodo goiter. It is very common checkups are usually required to ensure the proper among Japanese, as they take in about 8-25 dosage of thyroid hormones is taken. A patient micrograms iodine per day in the form of sea usually takes thyroid hormones for the rest of his/ weeds. her life. Goiter can be treated by taking iodinated Laevothyroxine, Eltroxin, is popularly tablets and consumption of iodinated in the used by oral route in hypothyroidism. daily diet. Treatment for Hyperthyroidism: Hashimoto Goiter:- Specific treatment for hyperthyroidism will It is an which occurs be based on type of hyperthyroidism. in middle aged females due to sensitization of their Treatment may include use of anti thyroid own thyroid protein called thyroglobulin. drugs such as carbimazole (Neomarkazole) that : help lower the level of thyroid hormones in the blood, use of radioactive iodine, in the form of a Thyroid function tests are common pill or liquid, which damages thyroid cells so that procedures performed to determine how well the production of thyroid hormones is slowed down, thyroid is functioning. Some of the most common surgery to remove part of the thyroid (the thyroid function tests include the following: - overactive nodule), use of beta blocking agents, 1) Blood Tests: - To measure the levels of which block the action of thyroid hormone on the T3, T4, TSH and a protein called thyroxine body. binding globulin (TBG) in the blood which helps Goiter: determine thyroid function. Any enlargement of the thyroid, 2) Ultrasound of the thyroid gland: - To regardless of cause, is called goiter. It is a non- detect signs of growth and other irregularities. inflammatory and non-neoplastic enlargement of thyroid gland. Goiter is of several types, like 3) Thyroid Scans: - Using radioactive iodine or , a radioactive metallic element to a) Simple goiter: - It is also called reveal any physical abnormalities of the thyroid. goiter. 4) Functional stimulation test: - Tests that b) Endemic goiter: - It occurs in certain areas in help differentiate whether the problem lies with northern hilly areas where soil and ground water the pituitary gland or the thyroid gland. One such are deficient in iodine. test includes injecting thyrotropin releasing c) Colloidal goiter: - A greatly enlarged thyroid hormone (TRH) and measuring the pituitary’s in which the follicles are distended with colloids. response.

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Other tests are Thyroid Antibodies’ Test, Chaudhari, S. K. (2001). Concise Medical Physiology. Thyroid Needle Biopsy, and measurement of New Delhi : New Central Book Agency Pvt. Ltd. serum thyroid hormones (T3, T4) by RIA Jain, A.K. (2004), Textbook of Physiology, Volume II. (radioimmunoassay). Himachal Pradesh : Avichal Publishing Company. CONCLUSION Neal, Ernest.G., & Neal, Keith.R.C. (1990). for Today, Frome, Somerset, United Kingdom : Butler & Thyroid plays very vital role in human Tanner Ltd. beings. It is associated with physical, mental and Websites: sexual functioning of our body. Thyroid gland and Answers. (n.d.). Thyroid Gland. Retrieved from http:// memory are very much related so also it is related www.answers.com/topic/thyroid-1. to many other important functions of our body. Medicine Net.com. (n.d.) Definition of Thyroid Many findings prove that proper functioning of Hormones. Retrieved from http://www.medterms.com / thyroid is very much necessary as it controls the script/main/art.asp?article key=5780 body’s metabolism and maintains proper calcium Thyroid. (n.d.) In Laborlawtalk Encyclopedia. level. People should be aware of diseases related Retrieved from http://www.encyclopedia. to thyroid gland and should take utmost laborlawtalk.com/Thyroid precautions to avoid them by taking iodized salt, University of Maryland Medical Centre. (n.d.). sea food in their daily diet. As we all know Health Guide. The Thyroid Gland. “prevention is better than cure”. Retrieved from http://www.umm.edu / endocrin / thygland.htm Reference :

Books : Soma Mishra, C/o- Manas Mishra, Tech. Head, Tech Bhatti, K. (2004) A to Z in Biology. Jalandhar City ! Mahindra, Rajiv Gandhi Infotech Park, Hinjewadi S. Dinesh & Co. Phase-3, Pune-411057, Maharashtra.

The Chairperson, Odisha State Commission for Protection of Child Rights Smt. Saraswati Hembrum inaugurating the Adoption Awareness Week at Subhadra Mahatab Seva Sadan, Bhubaneswar.

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VOL. LXIX NO. 5 DECEMBER - 2012

PRADEEP KUMAR JENA, I.A.S. Commissioner-cum- Secretary

DEBENDRA PRASAD DAS, O.A.S.(SAG) Director

DR. LENIN MOHANTY Editor

Editorial Assistance Bibhu Chandra Mishra Bikram Maharana

Production Assistance Debasis Pattnaik Sadhana Mishra

Manas R. Nayak Cover Design & Illustration

Hemanta Kumar Sahoo D.T.P. & Design

Raju Singh Manoranjan Mohanty Photo

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