Seventy-three children with disorders of physical growth and mental development were stimulated by insulin hypoglycemia and arginine infusion and their human growth hormone (HGH) responses were determined. Only four patients exhibited absent or impaired pituitary hormone secretion and one of them presented a unique syndrome of panhypopituitarism associated with intrauterine growth retardation, long eyelashes and eyebrows, sparse hair and degeneration of the retina. Statistical analysis indicated no significant HGH peak concentrations in groups of either tall males or stunted females who possessed various sex chromosome abnormalities, nor did these groups differ in a variety of clinical parameters including age, physical growth, birth weight and intelligence.