Context and Objective: In men with infertility secondary to gonadotropin deficiency, treatment with relatively high dosages of human chorionic gonadotropin (hCG) stimulates intratesticular testosterone (IT-T) biosynthesis and spermatogenesis. Previously we found that lower dosages of hCG stimulated IT-T to normal. However, the minimal dose of hCG needed to stimulate IT-T and the dose-response relationship between very low doses of hCG and IT-T and serum testosterone in normal men is unknown.
Design, Setting, Patients, and Intervention: We induced experimental gonadotropin deficiency in 37 normal men with the GnRH antagonist acyline and randomized them to receive one of four low doses of hCG: 0, 15, 60, or 125 IU sc every other day or 7.5 g daily testosterone gel for 10 d. Testicular fluid was obtained by percutaneous aspiration for steroid measurements at baseline and after 10 d of treatment and correlated with contemporaneous serum hormone measurements.
Results: Median (25th, 75th percentile) baseline IT-T was 2508 nmol/liter (1753, 3502 nmol/liter). IT-T concentrations increased in a dose-dependent manner with very low-dosage hCG administration from 77 nmol/liter (40, 122 nmol/liter) to 923 nmol/liter (894, 1017 nmol/liter) in the 0- and 125-IU groups, respectively (P < 0.001). Moreover, serum hCG was significantly correlated with both IT-T and serum testosterone (P < 0.01).
Conclusion: Doses of hCG far lower than those used clinically increase IT-T concentrations in a dose-dependent manner in normal men with experimental gonadotropin deficiency. Assessment of IT-T provides a valuable tool to investigate the hormonal regulation of spermatogenesis in man.
