Purpose: Growth hormone (GH) replacement decreases insulin sensitivity in healthy individuals. However, the effects of GH on organ-specific insulin sensitivity and glucose effectiveness are not well characterized. The purpose of this study was to evaluate the effects of GH administration for 26 weeks on muscle and hepatic insulin sensitivity and glucose effectiveness in healthy older individuals.
Methods: This report is from a 26-week randomized, double-blind, placebo-controlled parallel-group trial in healthy, ambulatory, community-dwelling older women and men. We compared surrogate indices of insulin sensitivity [quantitative insulin-sensitivity check index (QUICKI), muscle insulin sensitivity index (MISI), hepatic insulin resistance index (HIRI)] and glucose effectiveness [oral glucose effectiveness index (oGE)] derived from oral glucose tolerance tests (OGTTs) in subjects before and after 26 weeks of administration of GH (n = 17) or placebo (n = 15) as an exploratory outcome.
Results: GH administration for 26 weeks significantly increased fasting insulin concentrations and HIRI but did not significantly change MISI or oGE compared to placebo.
Conclusions: GH administration for 26 weeks in healthy older subjects impairs insulin sensitivity in the liver but not skeletal muscle and does not alter glucose effectiveness.
Keywords: Aging; Glucose effectiveness; Growth hormone; Insulin resistance.