OVERVIEW OF THE NATIONAL COOPERATIVE GROWTH STUDY SUBSTUDY OF SERIAL GROWTH-HORMONE MEASUREMENTS

For the National Cooperative Growth Study II substudy, data on spontan eous growth hormone (GH) secretion were collected from 5106 children w ith short stature, Of these, 2123 with complete 12-hour samples were s ubsequently enrolled in the NCGS. Compared with NCGS enrollees who wer e not in the NCGS II substudy, these children were significantly older (11.3 +/- 3.3 years vs 9.9 +/- 4.2 years), had a higher maximum repor ted GH level (13.3 +/- 10.5 mu g/L vs 9.2 +/- 8.7 mu g/L), and were mo re likely to be male (71% vs 62%) and pubertal (27.3% vs 21.9%) (p<0.0 01 for all), Height deficit, bone age delay, and pretreatment growth r ates were similar. Children who were classified as having GH deficienc y on the basis of their response to standard pharmacologic tests had l ower spontaneous GH secretion than those who were classified as having idiopathic short stature, but considerable overlap was seen between t he two groups on all indexes of spontaneous GH secretion. This finding suggests that the investigators were using serial sampling studies in examining children with short stature who were not growing well but h ad ''normal'' GH responses to standard pharmacologic testing.