Context: Sex steroid hormones potentiate whereas increased body mass index (BMI) represses GH secretion. Whether sex steroids modify the negative effect of BMI on secretagogue-induced GH secretion in men is not known. The issue is important in designing GH-stimulation regimens that are relatively insensitive to both gonadal status and adiposity. Objective: Our objective was to compare the relationships between BMI and peptide-stimulated GH secretion in men with normal and reduced testosterone and estradiol availability. Setting: The study was performed at an academic medical center. Subjects: Healthy young men were included in the study. Interventions: Randomized separate-day iv infusion of saline and/or maximally effective doses of L-arginine/GHRH, L-arginine/GH- releasing peptide (GHRP)-2, and GHRH/GHRP-2 in eugonadal (n = 12) and experimentally hypogonadal (n = 10) men was performed. Outcomes: Regression of paired secretagogue-induced GH responses on BMI was determined. Results: In eugonadal men, peak GH concentrations correlated negatively with BMI. In particular, BMI accounted for only 38% of the response variability after L-arginine/GHRH (P = 0.0165), but 62% after GHRH/GHRP-2(P = 0.0012)and65%after L-arginine/GHRP-2 (P = 0.00075). In contrast, inhypogonadal men, GH responses were uncorrelated with BMI. The negative effects of BMI on peak GH responses in eugonadal and hypogonadal states differed most markedly after stimulation with GHRH/GHRP-2 (P = 0.0019). This contrast was corroborated using integrated GH responses (P = 0.0007). Conclusions: Short-term experimental gonadal sex hormone depletion attenuates dual secretagogue-stimulated GH secretion in lean young men. The inhibitory effect of relative adiposity on GH secretion appears to predominate over that of acute sex steroid withdrawal.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical