The effect of the deterioration of insulin sensitivity on beta-cell function in growth-hormone-deficient adults following 4-month growth hormone replacement therapy

Abstract

The purpose of the present study was to evaluate the combined effect of GH treatment on body composition and glucose metabolism, with special focus on beta-cell function in adult GHD patients. In a double-blind placebo-controlled design, 24 GHD adults (18M/6F), were randomized to 4 months treatment with biosynthetic GH 2 IU/m2s.c. daily (n =13) or placebo (n =11). At inclusion and 4 months later an oral glucose tolerance test (OGTT), a frequently sampled intravenous glucose tolerance test (FSIGT) and dual-energy X-ray absorptiometry (DXA) whole-body scanning were performed. During the study period, body weight decreased 1.6 kg from 94.0 +/- 18.7 to 92.4 +/- 19.4 kg (mean +/- SD) (P<0.05) in the GH-treated group, but remained unchanged in the placebo group. Fat mass decreased from 32.4 +/- 9.6 to 28.1 +/- 10.5 kg (P<0.001), whereas lean body mass increased from 58.3 +/- 11.5 to 61.0 +/- 11.7 kg (P<0.01) in the GH-treated group. Treatment with GH for 4 months resulted in a significant increase in fasting blood glucose (before GH 5.0 +/- 0.3 and after 5.4 +/- 0.6 mmol/l, P<0.05), fasting plasma insulin (before GH 38.4 +/- 30.2 and after 55.3 +/- 34.7 pmol/l, P<0.02) and fasting proinsulin (before 8. 1 +/- 6.7 and after 14.6 +/- 16.1 pmol/l, P<0.05). The insulin sensitivity index SI, estimated by Bergmans Minimal Model, decreased significantly [before GH 1.1 +/- 0.7 and after 0.4 +/- 0.2 10(-4)(min x pmol/l), P<0.003]. The non-insulin-dependent glucose uptake (glucose effectiveness SG did not change (before GH 0.017 +/- 0.005 and after 0.015 +/- 0.006 min-1, NS). Insulin secretion was enhanced during GH therapy, but insufficiently to match the changes in SI, resulting in a higher blood glucose level during an OGTT. Blood glucose at 120 min was 5.5 and 6.3 mmol/l before and after GH treatment, respectively (P = 0.07). One patient developed impaired glucose tolerance. Short-term GH replacement therapy in a dose of about 2 IU/m2 daily in GHD adults induces a reduction in insulin sensitivity, despite favourable changes in body composition, and an inadequate enhancement of insulin secretion.