The regulation of growth hormone (GH) secretion in humans is a complex process which comprises more than stimulation by GH-releasing hormone and suppression by somatostatin. Although these two hypothalamic hormones are the primary regulators of GH secretion, they most likely function as the final pathway through which numerous factors influence GH synthesis and secretion. Some of the modulators of GH secretion include neurotransmitters, circulating glucose, insulin-like growth factor I and gonadal steroid concentrations. Age, nutrition and body composition are also related to the amount and pattern of GH secretion in humans. The influence of nutritional status on GH secretion is becoming more clearly defined.