Testicular Vein Sampling Can Reveal Gonadotropin-Independent Unilateral Steroidogenesis Supporting Spermatogenesis

Suppressed gonadotropins combined with high-normal serum testosterone concentrations in oligozoospermic men suggest either use of exogenous testosterone or presence of a testosterone-producing tumor. We describe the case of a 31-year-old man referred for primary infertility. Gonadotropins were undetectably low, but testosterone and estradiol were in the high-normal range. Semen analysis showed oligoasthenospermia. He denied using exogenous testosterone. Scrotal ultrasound showed microlithiasis and millimetric hypolucent lesions in the left testis but no intratesticular mass. Human chorionic gonadotropin was low. To investigate unilateral hormone secretion, selective testicular venous sampling was performed. Testosterone and estradiol were clearly higher on the left side than on the right (130 vs 26 nmol/L and 1388 vs 62 pmol/L, respectively), with a left spermatic vein-to-periphery gradient of 4.3 for testosterone and 13 for estradiol; there were no similar gradients on the right side. This finding confirms that all sex steroid secretion came from the left testis. The patient was therefore referred for left orchidectomy. Histopathology revealed multifocal seminoma, germ cell neoplasia in situ, and Leydig cell hyperplasia but no choriocarcinoma. However, gonadotrophin levels increased after orchidectomy, indicating that the source of gonadotropin-independent sex steroid secretion was removed. Testosterone and estradiol decreased to the mid-normal range. Sperm concentration improved. This report thus shows that endogenous testosterone secretion in one testicle supports spermatogenesis without measurable levels of gonadotropins. Selective testicular venous sampling is useful to identify the site of unilateral secretion when the clinical picture is inconclusive. However, histopathology could not reveal the factor that stimulated Leydig cell steroidogenesis.