Caloric restriction for 24 hours increases mean night growth hormone

In obesity, serum growth hormone (GH) is usually low, confounding GH assess ment of short obese children. We evaluated whether 24-h caloric restriction would permit better discrimination between normal GH secretion and GH defi ciency (GHD) by elevating night GH levels. Design and patients: Serum was obtained every 20 minutes 2000-0800h before and 2200-0400h after 24 hours of caloric restriction (8% of usual calories) in 24 normal height children [14 normal (weight for height 10-90th percent ile); 10 obese (weight for height >95th percentile)] and in 31 short childr en (height shouter than -2.0 SD below mean for age). All samples from both nights per child were assayed for GH simultaneously to eliminate interassay variability. Results: Mean GH increased significantly in all groups after caloric restri ction (P<0.01). Obese children had lower baseline mean GH and GH amplitude compared to normal (P<0.01); GH increased into normal range after restricti on. Basal GH studies in short children were not significantly below normal. Surprisingly, some with low stimulated GH increased their night GH into th e normal range after caloric restriction. Conclusions: Caloric restriction for 24 h enhances night GH similarly in sh ort and in normal children, and thus does not increase the diagnostic utili ty of night GH studies in non-obese short children. Caloric restriction rev erses suppressed GH secretory state of obese children, perhaps by decreasin g diet-dependent somatostatin inhibition of GH secretion.