Physiology of growth hormone secretion and action.

Growth hormone secretion by the pituitary gland is dependent on the dual regulation exerted by growth hormone-releasing hormone and somatostatin, which are the final integrative pathways for several signals reaching the hypothalamus. Regulatory signals include neurotransmitters, neuropeptides, and peripheral signals such as hormones or nutrients. In the circulation, growth hormone is bound to specific binding proteins and, by activating specific receptors, exerts a variety of peripheral actions.