question_answer 5)

Write short notes on the functions of the following hormones (a) Parathyroid hormone (PTH) (b) Thyroid hormones (c) Thymosins (d) Androgens (e) Oestrogen (f) Insulin and Glucagon  

Answer:

Functions of the following hormones are as follows (a) Parathyroid Hormone (PTH) The parathyroid glands secrete a peptide hormone called parathyroid hormone (PTH). PTH acts on bones and stimulates the process of bone resorption (dissolution/demineralization). PTH also stimulates reabsorption of by the renal tubules and increases absorption from the digested food. It plays a significant role in calcium balance in the body. (b) Thyroid Hormones Thyroid hormones play an important role in the regulation of the basal metabolic rate. These hormones also support the process of red blood cell formation. Thyroid hormones control the metabolism of carbohydrates, proteins and fats. The Maintenance of water and electrolyte balance is also influenced by thyroid hormones. Thyroid gland also secretes a protein hormone called thyrocalcitonin (TCT), which regulates the blood calcium levels. (c) Thymosins This thymus gland secretes the peptide hormones called thymosins. Thymosins play a major role in the differentiation of T-lymphocytes, which provide cell-mediated immunity. In addition, thymosins also promote production of antibodies to provide humoral immunity. (d) Androgens Androgens regulate the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra, etc. These hormones stimulate muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice, etc. Androgens play a major stimulatory role in the process of spermatogenesis (formation of spermatozoa), influence the male sexual behaviour (libido). (e) Oestrogens Oestrogens produce wide ranging actions such as stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g., high pitch of voice, etc.), mammary gland development. Oestrogens also regulate female sexual behaviour. (f) Insulin and Glucagon Glucagon acts mainly on the liver cells (hepatocytes) and stimulates glycogenolysis resulting in an increased blood sugar (hyperglycemia). In addition, this hormone stimulates the process of gluconeogenesis, which also contributes to hyperglycemia. Glucagon reduces the cellular glucose uptake and utilization. Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis. Insulin acts mainly on hepatocytes and adipocytes and enhances cellular glucose uptake and utilisation. Insulin also stimulates conversion of glucose to glycogen (glycogenesis) in the target cells. The glucose homeostasis in blood is thus maintained jointly by the two - insulin and glucagons.