Unchanged testosterone production rates in growth hormone treated healthy men

The effect of biosynthetic human GH on the production rates of testosterone was determined in healthy men (n = 7) using the stable isotope dilution technique and mass spectrometry, 1 alpha,2 alpha-d-Testosterone (20 mu g/h) was infused for 10 h (0800-1800 h). Blood samples obtained at 20-min intervals from 1400-1800 h were pooled during two 2-h periods. Subsequently, each volunteer received a daily dose of biosynthetic human GH (4 IU/day sc) for 7 days. This resulted in a rise in plasma concentrations of somatomedin-C from, basal, 0.67 +/- 0.13 U/mL to 1.20 +/- 0.2 U/mL on day 7 (P < 0.0001). Testosterone production rates (basal: 209.9 +/- 31.0 mu g/h) were unchanged by treatment with GH (day 7: 192.2 +/- 30.1 mu g/h). In healthy men, short-term treatment with sc GH does not influence endogenous testosterone production rates.