Studies of Growth Hormone Secretion in Children: Normal, Hypopituitary and Constitutionally Delayed

Plasma growth hormone levels in normal children, in children with pituitary or hypothalamic disorders, in children with idiopathic growth hormone deficiency and in children with a constitutional delay in growth were examined in the fasting state and following stimulation with insulin hypoglycemia, arginine and bacterial pyrogen (Piromen). Normal children exhibited a marked fluctuation in fasting growth hormone levels. The highest plasma growth hormone levels were observed after insulin, but the mean maximal levels in response to each of the stimuli were not statistically different from one another because of a marked variation in response. Four children with a constitutional delay in growth had plasma growth hormone values indistinguishable from those of normal children. Seven children with idiopathic growth hormone deficiency had fasting and post-stimulatory plasma growth hormone levels significantly lower than normal children. In subjects with known pituitary or hypothalamic disorders virtually no elevations in plasma growth hormone levels occurred following stimulation. The levels in these subjects were lower than in some of the children with idiopathic growth hormone deficiency. The results suggest that 1) constitutional delay in growth is not associated with abnormalities in growth hormone responses to the stimuli used, 2) children with idiopathic growth hormone deficiency have significantly lower pre- and poststimulatory growth hormone levels than do normals, and 3) the lack of response to stimulation occasionally seen in normal children is often associated with high resting levels of growth hormone.