Chronic human chorionic gonadotropin administration in normal men: evidence that follicle-stimulating hormone is necessary for the maintenance of quantitatively normal spermatogenesis in man.

The role of FSH in the maintenance of spermatogenesis in man is poorly understood. To determine whether normal serum levels of FSH are necessary for the maintenance of quantitatively normal spermatogenesis, we first studied the effect on sperm production of selective FSH deficiency induced by chronic administration of hCG in normal men. Then, we determined the effect of FSH replacement in some of these men. After a 3-month control period, eight normal men (aged 30-39 yr) received 5000 IU hCG, im, twice weekly for 7 months. Then while continuing the same dosage of hCG, subjects simultaneously received 200 mg testosterone enanthate (T), im, weekly for an additional 6 months. hCG administration alone resulted in partial suppression of the mean sperm concentration from 88 +/- 24 (+/-SEM) million/ml during the control period to 22 +/- 7 million/ml during the last 4 months of hCG treatment (P less than 0.001 compared to control values). With the addition of T to hCG, sperm counts remained suppressed to the same degree. Except for one man who became azoospermic while receiving hCG plus T, sperm motilities and morphologies remained normal in all subjects throughout the entire study. During both the hCG alone and hCG plus T periods, serum FSH levels were undetectable (less than 25 ng/ml), and urinary FSH levels were comparable to those in prepubertal children and hypogonadotropic hypogonadal adults. We replaced FSH activity in four of the eight men in whom prolonged selective FSH deficiency and partial suppression of sperm production were induced by hCG administration. Immediately after the period of hCG plus T administration, T was stopped in four men who continued to receive hCG alone (5000 IU, im, twice weekly) for 3 months. Then, while continuing the same dosage of hCG, these men received 100 IU human FSH, sc, daily (n = 2) or 75 IU human menopausal gonadotropin, sc, daily (n = 2) for 5-8 months. During the second period of hCG administration alone, serum FSH levels were undetectable (less than 25 ng/ml), and sperm concentrations were suppressed (34 +/- 13 million/ml) compared to the control values for these four men (125 +/- 39 million/ml; P less than 0.001). With the addition of FSH to hCG, FSH levels increased (213 +/- 72 ng/ml) and sperm concentrations rose significantly, reaching a mean of 103 +/- 30 million/ml (P less than 0.03 compared to hCG alone).(ABSTRACT TRUNCATED AT 400 WORDS)