Gonadotropin Suppression in Normal Males and Males with 1° Hypogonadism: Evaluation of Four Androgens

Serum concentrations of FSH and LH have been evaluated during treatment with four commonly prescribed androgens. In the first study, five adult males with primary gonadal failure were treated for four weeks with each of four regimens: 17α‐methyl testosterone [MT] (40 mg/day or 50 mg/day), fluoxymesterone [F] (50 mg/day), and testosterone cypionate [TC] (200 mg). LH was not suppressed by either dose of MT but was suppressed by F (P < 0.02). Both FSH and LH were suppressed for up to 3 weeks (P < 0.05) after a single injection of TC. In the second study, testosterone enanthate [TE] was evaluated as a contraceptive in 20 normal men. After two weeks (200 mg/week), the concentration of testosterone increased from 661 ± 29 ng/dl to approximately 1050 ng dl (P < 0.001) and serum gonadotropins had fallen to very low or undetectable levels. After 12 weeks of this regimen, 11 men had ≤ 1 million sperm/ml of semen, but 3 had ≥ 10 million sperm/ml. When 200 mg of TE was given every 3 weeks, serum levels of FSH and LH normalized and sperm density increased. These studies indicate that exogenous androgens can be used to suppress gonadotropins and spermatogenesis; however, each of these four available androgens has limitations. A more potent, longer acting androgen with low toxicity is needed if this approach to the development of a male contraceptive is to be pursued.