LOW CONCENTRATIONS OF INSULIN-LIKE GROWTH FACTOR-I IN ABDOMINAL OBESITY

Growth hormone secretion is blunted in obesity. Recent studies have shown that the sub-group of obesity with preponderance of accumulation of fat in visceral depots is associated with endocrine abnormalities. We therefore measured IGF-I concentrations in serum in 27 men who also underwent computerized tomography measurements of regional and total body fat mass. Furthermore, euglycemic-hyperinsulinemic glucose clamps were used to determine insulin resistance, and established 'risk factors' for cardiovascular disease and non-insulin dependent diabetes mellitus were measured, i.e. blood pressure, plasma lipids, and blood glucose, as well as sex steroid hormones. Visceral fat mass systolic blood pressure and triglycerides were higher (P < 0.05) in the group with low (87 +/- 4 mug/l) IGF-I values, compared to those with high (126 +/- 6 mug/l) IGF-I values, divided after the median value. IGF-I was negatively correlated with visceral fat mass (r = 0.40), independently of subcutaneous and total fat mass. As described before visceral fat mass was directly associated to a majority of the measured 'risk factors', as well as indirectly to testosterone and sex hormone binding globulin (SHBG) concentrations. The latter were also strongly related statistically to the 'risk factors'. IGF-I concentrations showed, however, weaker correlations with the metabolic factors, blood pressure or sex steroid hormones. Multivariate analyses revealed that the correlations of visceral fat with the risk factors were not influenced by IGF-1, while testosterone or SHBG totally abolished these associations. The results indicate that low serum IGF-I concentrations, suggesting deficient growth hormone secretion, are associated with visceral but not with subcutaneous or total fat masses. It was suggested that the metabolic complications of visceral obesity are mainly independent of low IGF-I.