GH-binding protein in obese men with varying glucose tolerance: relationship to body fat distribution, insulin secretion and the GH-IGF-I axis

Bioelectrical impedance for measurement of total body fat and computed tomography for visceral and subcutaneous fat at umbilicus levels were performed in 34 obese and 10 lean men. Insulin secretion in response to an oral glucose tolerance test (OGTT) and a GH stimulation test by L-dopa, growth hormone-binding protein (GHBP) and IGF-I were measured. Obese subjects were divided into three groups according to the OGTT. The obese type II diabetes mellitus group had the highest GHBP levels and the most visceral fat. GHBP levels were most strongly correlated with the ratio of visceral fat area to body weight (VWR) above any other parameters (r = 0.725, P<0.001). The insulin and free fatty acid (FFA) areas under curves (AUC) during the OGTT, and the IGF-I level, were also positively correlated with GHBP levels (r = 0.474, P<0.005; r = 0.572, P<0.005; r = 0.453. P<0.005). GH-AUC to the L-dopa stimulation test was negatively correlated with GHBP levels (r = -0.432. P