Leydig cell tumor: a case report with reference to its endocrinological features.

We reported an adult case of Leydig cell tumor, which demonstrated an increase of serum estradiol (E2) and suppression of serum testosterone (T) before orchiectomy. The direct inhibitory action of the elevated E2 on the enzymes involved in steroidogenesis and the negative feedback action on luteinizing hormone (LH) secretion of the E2 possibly caused the suppression of serum T. A human chorionic gonadotropin test before the operation revealed the elevation of T and E2, although the response was poor compared with that in normal subjects. However, the postoperative test showed no elevation of these hormones. This result may indicate that the Leydig cell tumor preserves a response to LH stimulation.