Effects of treatment with recombinant human growth hormone on insulin sensitivity and glucose metabolism in adults with growth hormone deficiency.

In a double-blind, cross-over, placebo-controlled trial, the effect of 26 weeks of replacement therapy with recombinant human growth hormone (rhGH) on insulin sensitivity and glucose metabolism in nine patients with adult-onset growth hormone deficiency was studied with a euglycemic clamp. Glucose production and utilization were studied with D-(3-3H)-glucose infusions. Comparisons were made with placebo treatment for 6 and 26 weeks, respectively. GH therapy for 6 weeks increased fasting plasma concentrations of glucose and insulin. However, after 26 weeks of GH treatment, no significant changes in glucose or insulin concentrations were recorded. GH treatment induced a marked change in insulin action evident after 6 weeks of therapy as shown by lower glucose infusion rates (GIRs) during the clamp compared with placebo treatment (2.6 +/- 0.4 v 4.1 +/- 0.7 mg.kg-1.min-1). This change in insulin action was due to a decreased insulin effect on glucose utilization. After 26 weeks of GH therapy, there was no significant difference in GIRs. During placebo treatment, insulin sensitivity and insulin, glucose, and nonesterified fatty acid (NEFA) concentrations were unchanged compared with concentrations measured before the study. Thus GH replacement therapy induces a change in insulin action in GH-deficient individuals. Whether this change represents a decrease in insulin action (ie, insulin resistance) or a restoration of action to normal is presently unclear, since a healthy control group was not included in the study. During long-term treatment, the present study suggests that the change in insulin action can be reversed, probably secondarily to changes in body composition.