Interleukin 1 receptor antagonist is associated with changes in body composition during physiological GH substitution in patients with adult-onset growth hormone deficiency.

Objective: We examined the effect of GH substitution on adipose tissue derived hormones and cytokines and sought to identify predictors for changes in body composition during therapy. Long-standing adult-onset GH deficiency (AO-GHD) is associated with increased body fat mass (FM) which, through production of hormones and inflammatory cytokines from adipose tissue, may contribute to different manifestations of the metabolic syndrome. Design, patients and measurements: Fifty-five patients with adult-onset GH deficiency (AO-GHD), (24 females, 31 males, mean age 49 years) were enrolled in a placebo-controlled, double-blind crossover study. GH therapy was individually dosed to obtain an IGF-I concentration within the normal range for age and sex. GH and placebo were administered for 9 months each, separated by a 4 month washout period. Adipose tissue derived cytokines were measured by enzyme immunoassay. Results: GH treatment was associated with a significant decrease in IL-1 receptor antagonist (IL-1Ra) compared to placebo, which correlated with declining body FM (truncal and total) after GH substitution. The change in IL-1Ra was the strongest predictor of the variation in BFM in regression models. No changes were observed for leptin, adiponectin, soluble TNF receptor 1 or interleukin (IL)-8. Conclusion: The data indicate a possible unrecognized association between IL-1Ra and changes in body composition during GH substitution, and suggest further research on the interaction between the GH-IGF axis and the IL-1 system.