Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Hormone replacement therapy (menopause) wikipedia , lookup
Metabolic syndrome wikipedia , lookup
Neuroendocrine tumor wikipedia , lookup
Hormone replacement therapy (male-to-female) wikipedia , lookup
Growth hormone therapy wikipedia , lookup
Hyperandrogenism wikipedia , lookup
Bioidentical hormone replacement therapy wikipedia , lookup
Hypothalamus wikipedia , lookup
Thyroid hormones Physiological effects of thyroid hormones Thyroid hormone synthesis Regulation of thyroid function Hypothyroidism Hyperthyroidism Parathyroid glands Parathormone (PTH) Hyperparathyroidism Hypoparathyroidism Calcitonin (CT) (Thyrocalcitonin) Thyroid hormones The thyroid gland is a small gland situated in the neck, wrapped around the trachea just below the larynx (voice box). It secretes hormones that increase the metabolic rate and oxygen consumption and that are necessary for proper growth and development. The thyroid also secretes calcitonin (hormone that participates in regulation of plasma Ca2+concentration by inhibiting bone resorption. The thyroid hormones thyroxine (T4) 3,5,3',5‘ tetraiodothyronine and 3,5,3'triiodothyronine (T3) Physiological effects of thyroid hormones 1) Thyroid hormones stimulate protein synthesis. 2) Promotes intestinal absorption of glucose and may cause hyperglycemia. 3) Have tendency to lower the serum cholesterol. 4) Increase both the rate of secretion of digestive juices and the motility of the GIT. 5) Increase the rate of depth of respiration. 6) In males lack of thyroid hormones is likely to cause complete loss of libido (sexual desire), whereas on the other hand much more excess of thyroid hormones causes impotence. 7) In female, excess of thyroid hormones causes menorrhoea or polymenorrhoea which means excessive and frequent menstrual bleeding, respectively. Lack of thyroid hormones may cause irregular period or even total amenorrhoea. Thyroid hormone synthesis Thyroxine (T4) 3,5,3',5‘ tetraiodothyronine and small amounts of tri-iodothyronine (3,5,3'triiodothyronine) (T3) and reverse T3 (rT3) (3, 3',5'triiodothyronine) are all synthesised in the thyroid gland. Their immediate precursors are monoiodotyrosine (MIT) and diiodotyrosine (DIT), these compounds do not appear in plasma. Neither MIT nor DIT has any hormonal activity. Thyroid hormones production 1) Entry of inorganic iodide ion into the thyroid cell. 2) I- oxidized with help of a peroxidase enzyme system. 3) Activated iodine react with tyrosyl residues in protein thyroglobulin. MIT and DIT are produced. 4) MIT and DIT are oxidatively coupled by enzyme system to form T3 , T4andrT3 residues attached to thyroglobulin. 5) T3 , T4, rT3 , MIT and DIT are formed by the action of protease. 6) MIT and DIT are enzymatically deiodinated and the I is recycled within the gland. 7) T3 T4 and rT3 diffuse through the thyroid cell wall into plasma where they are quickly bound by thyroid-binding globulin (TBG) Regulation of thyroid function The most important regulator of thyroid homeostasis is TSH. The production of TSH is controlled by a stimulatory effect of the hypothalamic tripeptide, TRH, mediated by a negative feedback from circulating FreeT3 and FreeT4. It is thought that the hypothalamus, via TRH, sets the level of thyroid hormone production required physiologically, and that the pituitary acts as a ‘thyroid-stat’ to maintain the level of thyroid hormone production that has been determined by the hypothalamus. Thyroid hormones reference values Free T4 (reference range 10–21 pmol/L); Free T3 (reference range 2.6–6.2 pmol/L). Total T4 (reference range 70–150 nmol/L); Total T3 (reference range 1.2–2.8 nmol/L). Euthyroidism means level of thyroid hormones are normal Hypothyroidism • (FreeT4 low; TSH high) It is state in which there is not sufficient development of thyroid gland, in the embryonic life the child become a dwarf or cretin. A cretin grows slowly (stunted growth) and has a low mentality and low I.Q. his hair is scanty and coarse, and his skin is thick and dry. His basal metabolic rate (BMR) is low If the gland is removed or if it becomes subnormal in activity in adult, myxoedema develops. Myxoedema In myxoedema the skin becomes thick and dry and fall out. There is disinclination towards work either physically or mentally. There becomes a tendency to put on weight. The metabolic rate is reduced, nitrogen metabolism gets lowered, and the body temperature is subnormal . Ossification of bones is delayed Salient characteristics of hypothyroidism Tiredness Cramps or inflammation in muscles Tingling in fingers. Dry skin and intolerance of cold Yellow skin. Dry hairs or fall of hair Stress Decrease of heart beating Hoarseness of voice Goiter Loss of memory Loss of concentration Sterility or termination of pregnancy Myxoedema Irregular or heavy menses Hyperthyroidism • (FreeT4 and / or FreeT3 high; TSH low) It is a state in which the thyroid is too active, as a result of which condition known as exophthalmic goiter occurs. A common symptom of this disease is the bulging of the eyes. The disease also known as Grave's or Basedow's disease. The symptoms of exophthalmic goiter are the opposite of myxoaedema which mean that : symptoms of exophthalmic goiter 1) 2) 3) 4) 5) 6) 7) 8) The basal metabolic rate (BMR) is high. Nitrogen metabolism is increase. The hair fine. The body temperature is above normal. The patient is nervous and irritable. His mental is above rather than below normal. He or she is under weight. His/her heart beat is generally fast and irregular. Salient characteristics of hyperthyroidism Increase in heart beating (palpitations). Disappointment/dull/ irritation. Breathing problem. Irregular menses or complete loss of menses. Trembling of hand weakness Fall of hairs. Intolerance of heat. Increase of hunger. Increase of motility of intestine. Loss of weight. Hot and damp skin. To watch anything gazingly. Parathyroid glands There are 4 parathyroid glands, 2 are embedded in the posterior surface of thyroid gland ; and 2 lie close to and behind the thyroid. They are yellow-brown, egg shaped bodies. 2 hormones are known to be secreted by parathyroid glands: parathormone (PTH) and calcitonin (CT). Both PTH and CT are responsible for controlling calcium and phosphate metabolism in the human beings in a balancing manner. Parathormone (PTH) PTH is protein with molecular weight of 9500, consists of 83 amino acid residues composed of 17 different amino acids. Regulated by the level of circulating calcium. Low ionic calcium level stimulates whereas high ionic level inhibits PTH. PTH secretion is regulated by both calcium and magnesium. Hyperparathyroidism The main cause of hyperparathyroidism is the development of tumor. Hyperparathyroidism causes a syndrome known as osteitis fibrosa cystica which characterized by : 1) Hypercalcemia. 2) Hypophosphatemia. 3) Raised serum activity of alkaline phosphatase. Excessive demineralization of bone causes pain in them, deformities and spontaneous fractures. As a result of high calcium level in serum calculi may be formed in the kidney. other symptoms of this disorder also include : muscular asthenia, peptic ulcer, and constipation Hypoparathyroidism Hypoparathyroidism is more common than excessive secretion. It is caused by injury or removal of parathyroid glands during surgery of thyroid. Less secretion of PTH causes hypocalcaemia leading to muscle spasm, lenticular cataracts and calcification of the basal ganglia of the brain. Calcitonin (CT) (Thyrocalcitonin) Parathyroid hormone is the single and most important factor in fine regulation of blood calcium level ( extracellular and intracellular). Calcitonin is lowering calcium hormone. It is secreted by the parafollicular or “C” cells of the thyroid gland (hence the name thyrocalcitonin). Calcitonin is 32 amino acids with molecular weight 3000. Calcitonin has been synthesized in lab. The only known stimulus of CT secretion is a rise in plasma calcium. Level secretion is also stimulated by glucagon and cyclicAMP Raised in serum CT level is found in medullary thyroid carcinoma. CT may be administered in treatment of Paget's disease. There is no clinical syndrome of deficiency of CT.