Growth Hormone 101
Growth hormone, also called somatotropin, is a protein hormone consisting of roughly 190 amino acids (I think) and is produced in the anterior pituitary by cells called, conveniently enough, somatotrophs. Obviously, it is an important hormone in regulating growth and metabolism.
GH has both direct and indirect effects on growth and metabolism.
Direct effetcs: It binds to receptors on the surface of adipocytes (or fat cells) and causes the break down of their triglycerides and prevents those bastards from uptaking lipids floating in the blood stream.
Indirect effects: It stimulates the release of insulin-like growth factor-1 (IGF-1) from the liver (and other tissues) which then has a positive impact on growth.
IGF-1 stimulates bone growth as well as amino acid uptake and protein synthesis.
GH also moderates blood glucose levels. It interferes with insulin's ability to uptake glucose in tissues. Supplementing GH causes secretion of insulin and can cause hyperinsulinemia.
GH secretion is stimulated by Growth Hormone Releasing Hormone (GHRH which is produced by the hypothalamus) and is inhibited by somatostatin (SS) which is produced by the hypothalamus as well and by other tissues.
IGF-1 also acts ina negative feedback loop to inhibit production of GHRH, and GH itself, but stimulates the release of SS. Oh, and GH also inhibits the release of GHRH.
It's due to these feedback loops that the body has surges of GH throughout the day. The most noteable surge occurs within the first 2-3 hours that one enters into a deep sleep.
