ERYTHROPOIETIN STIMULATES TESTOSTERONE PRODUCTION IN MAN

Human recombinant erythropoietin (rHuEPO) treatment improves sexual fu nction in end-stage renal failure patients with a still-debated mechan ism. Experimental data suggested that rHuEPO was able to stimulate rat Leydig steroidogenesis; therefore, it has been suggested that rHuEPO may induce its effects in humans by acting on gonadal steroid producti on. Thirteen young adult males (age range, 16-28 yr) catheterized at p eripheral and left internal spermatic venous levels during a contrast study for varicocele, were studied. In five subjects, rHuEPO (60 IU/kg , up to a maximum of 4000 IU total) was injected over 1 min in the cub ital vein. Similarly, in other five patients, 50 mu g GnRH were infuse d. In three subjects, 2 mL saline were injected, as controls. Plasma L H, FSH, and testosterone (T) levels were then determined at -15, 0, 15 , 30, 45, 60, 90, and 120 min simultaneously in peripheral and spermat ic venous blood. rHuEPO infusion did not have any effect on plasma LH and FSH levels in peripheral or spermatic veins. Similarly, rHuEPO inf usion did not affect peripheral T concentration, but increased (simila r to 400% vs. controls; P < 0.05) spermatic T levels. GnRH infusion in duced an increase in plasma LH and FSH levels in both peripheral and s permatic veins. After GnRH infusion, an increase of approximately 12-f old (P = 0.05-0.001) in T was observed only at the spermatic venous le vel, without any peripheral T variation. These findings show that rHuE PO was able to influence testicular steroidogenesis by stimulating T p roduction in man, whereas the absence of any effect on gonadotropin se cretion suggests that rHuEPO might act directly on human Leydig cell f unction.