Conclusions
In older men, testosterone increases GH pulse frequency while the aromatization to estradiol is involved in the rise of IGF-1 levels.
Objective
This randomized controlled proof-of-concept trial investigated the relative effects of testosterone and estradiol on GH pulsatility and IGF-1 in older men with low testosterone. Design: Thirty-seven men, ≥65years with total testosterone <350ng/dL were randomized to 5g transdermal testosterone gel (TT), 1mg oral aromatase inhibitor (AI) or placebo daily for 12months. Primary outcome was deconvolution and approximate entropy analyses of pulsatile including basal and entropic modes of secretion performed at baseline and 3months. Secondary outcomes included IGF-1 evaluated at baseline, 3 and 6months.
Results
At 3months, mean GH and in IGF-1 were similar between the three groups. At 6months, IGF-1 significantly increased by Δ 15.3±10.3ng/ml in the TT-group compared to placebo (P=0.03). Both intervention groups significantly increased GH pulse frequency (TT-group, P=0.04; AI-group, P=0.05) compared to placebo. The GH secretory-burst mode (duration) significantly decreased in the TT-group (P=0.0018) compared to placebo while it remained unchanged in the AI-group (P=0.059). Conclusions: In older men, testosterone increases GH pulse frequency while the aromatization to estradiol is involved in the rise of IGF-1 levels.