Leydig cell tumor with gynecomastia: hormonal effects of an estrogen-producing tumor.

A patient with a testicular interstitial cell tumor and gynecomastia is reported. The testicular tumor was capable of aromatizing 8.3% testosterone. Spermatic venous samples taken from the tumor-bearing side had marked elevations of 17 beta-estradiol (E2), progesterone, and 17-hydroxyprogesterone (170 HP). The progesterone to 17OHP and 17OHP to androstene-dione ratios suggested an enzymatic block of 17 alpha-hydroxylase and 17-20 lyase possibly secondary to locally produced E2. The E2 produced by the tumor appeared to suppress gonadotropin secretion. The plasma testosterone and gonadotropin levels rose within 7 days after the removal of tumor, and the gynecomastia began to decrease.