Abdominal adiposity rather than age and sex predicts mass and regularity of GH secretion in healthy adults

We tested the hypothesis that body composition is the major predictor of growth hormone (GH) secretion in nonobese adults. We measured lean and fat tissue distribution (computerized tomography and dual-energy X-ray absorptiometry scan) and physical fitness [maximal oxygen consumption (V̇O₂(max)) in 42 healthy nonobese adults C22 women and 20 men, age range 27-59 yr, mean ± SE body mass index = 24 ± 0.5 kg/m²). Deconvolution analysis was used to estimate specific features of 24-h GH secretion and clearance. Approximate entropy was used to quantify the regularity of GH release. Older subjects exhibited decreased estimates of GH secretion compared with younger subjects. Females had higher estimates of GH secretion, a longer GH half-life, and displayed more irregularity in GH release than males. Mean 24-h serum GH concentrations correlated inversely with intra- abdominal fat and waist-to-hip ratio and positively with V̇O₂(max). Multiple linear regression analysis revealed intraabdominal fat as the dominant determinant of estimates of GH secretion. V̇O₂(max) was more important than sex and age in predicting GH secretion. We conclude that abdominal fat is the major determinant of GH secretion in healthy nonobese adults. Although the underlying mechanisms remain elusive, our findings extend the clinical implications of visceral adiposity to include hyposomatotropism.