Effect of growth hormone (GH) on fasting and postprandial metabolism in GH deficiency

Hypopituitarism with adult-onset growth hormone deficiency (GHD) is associated with increased cardiovascular morbidity and mortality due to premature and progressive atherosclerosis. An underlying cause of atherosclerosis is increased insulin resistance. Elevated fasting and postprandial glucose and lipid levels may contribute to premature atherosclerosis. We studied effects of growth hormone replacement (GHRT) on fasting and postprandial metabolic parameters as well as on insulin sensitivity in patients with adult-onset GHD.

Using a standardized mixed meal, we studied insulin, glucose, non-esterified free fatty acid (NEFA) and triglycerides (TG) concentrations in the fasting state and during a 4 h postprandial period in 15 patients with adult-onset GHD before and after 4 months of GHRT. Identical investigations were performed in healthy matched control subjects.

GHD patients before and after GHRT: GHRT did not result in significant changes in fasting glucose, insulin, NEFA and TG concentrations. In the postprandial period GHRT resulted in a non-significant increase in glucose and a decrease in NEFA levels in the presence of unchanged postprandial insulin and TG concentrations. GHD patients vs. control subjects: GHD patients showed similar fasting glucose, insulin and NEFA concentrations, but TG were increased. In the postprandial period GHD patients exhibited similar glucose and TG, but increased insulin and NEFA concentrations. GHRT patients vs. control subjects: Patients after GHRT had similar fasting glucose, insulin and NEFA, but increased TG concentrations. In the postprandial period patients after GHRT had increased glucose and insulin levels in the presence of similar NEFA and TG concentrations.

While impaired insulin action in patients with GHD translates mainly by an impaired fasting TG metabolism, GHRT induced insulin resistance additionally encompasses postprandial glucose metabolism.