Role of somatotropine in fat metabolism

Growth Hormone (GH) - i. It is also called somatotropin. It is a single polypeptide chain with 191 amino acids. GH is synthesized by acidophils (somatotropic cells) of anterior pituitary. ii. Plasma concentration of GH is less than 2 ng/ml during day time, with secretory peak appearing 3 hr after meals. Maximum level of GH is seen during deep sleep. For measurement of serum GH, the samples are collected during sleep and also during waking hours to assess the circadian rhythm. iii. GH secretion is regulated by the balance between GHRH and GHIH (somatostatin). The regulation of secretion is predominantly inhibitory. Hypoglycemia stimulates GH secretion, and hyperglycemia suppresses it. The hypothalamic growth hormone releasing hormone (GHRH) stimulates GH synthesis and release. Ghrelin, a peptide derived from stomach induces GHRH and directly stimulates the release of GH. Somatostatin synthesized in the hypothalamus inhibits the GH secretion. iv. The metabolic effect of GH is paly mediated by somatomedin, also known as insulin-like growth factor1 (IGF-1). The growth of long bones is stimulated by this factor. IGF-1, the peripheral target hormone of GH exes feedback inhibition. v. GH increases the uptake of amino acids by cells; enhances protein synthesis, and produces positive nitrogen balance . The anti-insulin effect of GH causes lipolysis and hyperglycemia. The overall effect of GH is to stimulate growth of soft tissues, cailage and bone. It is anabolic. vi. Excess secretion by GH secreting tumor, leads to gigantism in children and acromegaly in adults. REF:DM VASUDEVAN TEXTBOOK OF BIOCHEMISTRY, SIXTH EDITION, PG.NO.,530.