Suppression of pituitary and testicular function in normal men by constant gonadotropin-releasing hormone agonist infusion.

In a trial for male fertility control the effects of constant GnRH agonist (buserelin) infusion on pituitary and testicular function was investigated. The agonist was administered sc for 12 weeks to two groups of normal young men using extracorporeal osmotic minipumps. Seven men received 118 +/- 24 (SD) micrograms/day from pumps changed biweekly and four men received 230 +/- 27 micrograms/day from pumps changed weekly. After an initial rise serum LH, FSH, and testosterone decreased. The decrease occurred faster in the high dose group and these subjects had no LH response to acute GnRH stimulation after 4 weeks of treatment, whereas the response was drastically reduced in the group receiving the low dose. Androgen substitution with testosterone undecanoate (80-120 mg orally daily) was initiated when the subjects complained of decreased libido and/or potency or when serum testosterone fell below 10 nmol/liter on average in the fifth week. Sperm counts decreased significantly and below the lower normal limit of 20,000,000/ml. The nadir was reached in week 12 of treatment in the high dose group, and in week 4 post treatment in the low dose group. Despite desensitization of the pituitary and impaired testicular function azoospermia did not occur. A higher dose of agonist appears to be required to achieve this goal.