Human Growth Hormone (HGH)
This is most abundant growth hormone synthesized by anterior pituitary.
Function
1. It stimulate growth and division of most body cells but especially in bones, skeletal muscle.
2. Stimulation of epiphyseal plate lead to long bone growth, stimulation of skeletal muscle and promotes increased muscle mass.
3. Growth Hormone promotes synthesis and secretion of small protein hormone. These growth promoting protein hormones are produced by liver, skeletal muscle, bone and other tissues in response to human growth hormone.
4. It also regulate aspects of metabolism in many organ liver, intestine, and pancreas; stimulate protein synthesis, especially growth and repair; promotes breakdown of fats and increases blood glucose level.
5. Body growth in response to secretion of growth hormone is evident during childhood and adolescence.
Regulation of Secretion
Secretion of growth hormone is regulated chiefly two Hypothalamic hormone;
Growth hormone releasing hormone (GHRH)
Growth hormone inhibiting hormones (GHIH) called somatostatin.
GHRH (growth hormone releasing hormone) is stimulated by low blood levels of growth hormone.
Secretion of growth hormone (GH) is greater at night during sleep and is also stimulate by hypoglycemia, excercise and anxiety.
The daily amount of GH secretion peak in adolescence and the decline with age.
Inhibition of GH secretion occurs by negative feedback mechanism when blood sugar level rise and also when GHRIH (growth hormone release inhibiting hormone) is released by hypothalamus.
GHIH release is triggered by feedback of growth hormone and IGFs (insulin like growth factor).
Raising level of GH feedback to inhibit it own release.
GHIH blocks release of thyroid-stimulating-hormone. GHIH is also inhibit release of gastrointestinal secretion, pancreatic secretion.
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