Dose-Dependent Effect of Growth Hormone Therapy on Glucose Metabolism in Subjects with Turner Syndrome

Abstract

Recombinant human growth hormone (GH) is effective in promoting growth velocity in subjects with Turner syndrome. As higher doses are used for this indication than for substitution therapy in GH deficiency, the long-term effects of GH therapy on carbohydrate metabolism represent a safety issue; this is particularly important in Turner syndrome, in which there is an increased prevalence of impaired glucose tolerance. So far, GH therapy has been given to patients with Turner syndrome for up to 7 years without any significant changes having been reported in glycosylated haemoglobin (HbA_1c) values, unstimulated and stimulated oral glucose tolerance test (OGTT) blood glucose and serum insulin concentrations. These findings may, however, be influenced by other variables, such as study design, number of subjects or standardization methods applied. Results of an ongoing trial in the FRG, from which 2 years’ data on glucose metabolism (as assessed by serial OGTTs) of 72 patients with Turner syndrome are available, indicate that glucose homoeostasis is maintained at the expense of an increase in insulin secretion, which is time- and dose-dependent. Although these changes may be fully reversible on withdrawal of GH. therapy, accurate control of glucose metabolism both during and after GH. treatment is advocated.