(a) Parathyroid hormone (PTH):
(i) Parathyroid hormone (PTH) increase the Ca2+ levels in the blood.
(ii) PTH acts on bones and stimulates the process of bone resorption (dissolution/ demineralisation).
(iii) PTH also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food.
(iv) PTH is a hypercalcemic hormone, i.e., it
increases the blood Ca2+ levels body.
(b) Thyroid hormones:
(i) Thyroid hormones play an important role in the regulation of the basal metabolic rate.
(ii) These hormones also support the process of red blood cell formation.
(iii) Thyroid hormones control the metabolism of carbohydrates, proteins and fats.
(iv) Maintenance of water and electolyte balance is
also influenced by thyroid hormones.
(i) Thymosins play a major role in the differentiation of T-lymphocytes, which provide cell-mediated immunity.
(ii) In addition, thymosins also promote production of antibodies to provide humoral immunity
(i) Androgens regulate the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc.
(ii) These hormones stimulate muscular growth, growth of facial and axiliary hair, agressiveness, low pitch of voice etc.
(iii) Androgens play major stimulatory role in the process of spermatogenesis (formation of spermatozoa).
(iv) Androgens act on the central neural system and influeftce the male sexual behaviour (libido)
(v) These hormones produce anabolic (synthetic) effects on protein and carbohydrate metabolism.
(iy Estrogens produce wide range of 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.
(ii) Estrogens also regulate female sexual behaviour.
(i) Insulin is a peptide hormone, which plays a major role in the regulation of glucose homeostasis.
(ii) Insulin acts mainly on hepatocytes and adipocytes (cells of adipose tissue), and enhances cellular glucose uptake and utilisation.
(iii) Insulin also stimulates conversion of glucose to glycogen (glycogenesis) in the target cells.
(i) Glucagon is a peptide hormone, and plays as important role in maintaining the normal blood glucose levels.
(ii) Glucagon acts mainly on the liver cells (hepatocytes) and stimulates glycogenolysis resulting in an increased blood sugar (hyperglycemia).
(iii) In addition, this hormone stimulates the process of gluconeogenesis which also contributes to hyperglycemia.
(iv) Glucagon reduces the cellular glucose
uptake and utilization. Thus, glucagon is hyperglycemic hormone.
(h) Oxytocin : In females, it stimulates contraction of
the uterine muscles at the time of child birth and
milk ejection from the mammary gland.