Hormones and obesity: changes in insulin and growth hormone secretion following surgically induced weight loss.

Ten obese patients were subjected to insulin tolerance tests (0.2 unit per kg. regular insulin intravenously) and/or treadmill exercise tolerance testing (2.6 m.p.h. at 11 degrees angulation) before and after surgically induced weight reduction. Immunoreactive growth hormone (IRGH) responses returned to normal with weight reduction in all but one-a grossly obese woman studied relatively early in the postoperative period when still far from the ideal body weight. Five of these patients and two additional subjects had intravenous glucose tolerance tests (0.5 g. per kg.) before and after weight reduction. In all, there was a significant diminution in immunoreactive insulin (IRI) values, accompained by little or no change in the glucose disappearance rate (K(G)) and a significant improvement in insulin effectiveness as indicated by the calculated "insulinogenic index". It was concluded that the abnormalities in IRGH and IRI secretion, as well as the insulin resistance in obesity, are probably secondary and not of primary importance in the etiology of this disorder.