THE ROLE OF SERIAL SAMPLING IN THE DIAGNOSIS OF GROWTH-HORMONE DEFICIENCY

We analyzed 12-hour serial sampling of growth hormone (GH) levels in t wo cohorts of short children: 96 children referred to a university end ocrine clinic or studied on a research protocol and 825 children in th e National Cooperative Growth Study of children treated with exogenous GH. The mean 12-hour GH levels correlated with growth velocity in 60 children with normal height and growth velocity in the university stud y, and this correlation was stronger in the boys. The testosterone lev els also correlated with growth velocity and mean 12-hour GH levels in the boys. The mean 12-hour GH levels were lower in a group of 36 chil dren with idiopathic short stature than in the control subjects, as we re the peak GH levels within 1 hour after the onset of sleep and the i nsulin-like growth factor I levels. In the National Cooperative Growth Study cohort, pooled 12-hour GH levels were lower in the group with i diopathic GH deficiency (n = 300) than in the group with idiopathic sh ort stature (n = 525), but the difference was not significant. The dur ation of GH treatment was the most significant predictor of change in the height SD score in both groups. Indices of spontaneous secretion o f GH were not predictive of the response to GH treatment, nor were the results of provocative GH testing, the responses to GH treatment bein g similar in both groups over time. We conclude that the results of GH testing must be interpreted for each patient and that several testing modalities may be helpful in finding GH insufficiency that originates at various levels of the somatotropic axis.