Polycythemia and steroid overproduction in a gonadotropin-secreting seminoma of the testis.

While investigating the cause of mild polycythemia in a young man, a testicular seminoma was discovered with unusual and tumor-dependent features: an absolute polycythemia with high plasma erythropoietin (EPO) levels, an overproduction of estradiol and testosterone, and a dramatic Leydig cell hyperplasia surrounding the tumor tissue. The authors attempted to gain insight into the relationship between this testicular tumor and the hormonal overproduction, i.e., of EPO, estradiol, and testosterone. Their results favored the conclusion that the high EPO levels and the polycythemia were an indirect effect secondary to the steroid overproduction rather than a direct EPO-producing activity. Moreover, the steroid overproduction by the testis could be caused by a paracrine mechanism through human chorionic gonadotropin activity on the Leydig cells.