Alterations in steroidogenesis and human chorionic gonadotropin binding in the cryptorchid rat testis.

One month after the induction of cryptorchidism in adult rats, serum levels of LH and FSH were significantly elevated in comparison with sham-operated controls, whereas serum levels of testosterone remained low to normal. Testis weight in cryptorchid rats was reduced by over 66%, and once the extratubular fluid was removed by decapsulation, the reduction in weight was 78%. The basal production of testosterone, pregnenolone, and estradiol in vitro by testes from cryptorchid rats was similar to controls, whereas significantly less androstenedione was produced. Testicular stimulation in vitro with a high dose of hCG (360 pM) resulted in significantly greater production of testosterone, pregnenolone, and estradiol by cryptorchid than by control rat tissue. The in vitro binding of [125I]hCG per testis was decreased in the cryptorchid state to 40% of control values, probably as a result of down-regulation of LH receptors due to the 4-fold elevation of serum LH levels in the cryptorchid rats.