Suppression of serum testosterone concentrations in men by an oral contraceptive preparation.

Abstract

The suppression of serum testosterone levels in 5 normal men by an oral contraceptive (Eugynon 50 50 mcg ethinylestradiol plus 500 mcg norgestrel) is reported. The volunteers aged 21-39 took 1 tablet each day for 9 days. Testosterone levels measured by radioimmunoassay fell rapidly for the 1st 4 days and then continued to fall at a slower rate. On the 9th day the levels had fallen to 8% of the initial levels (.36 ng/ml). Following discontinuation of the drug the levels recovered fully within a week. All men experienced loss of libido during the latter 1/2 of the ingestion period. It is suggested that norgestrel alone or combined with small doses of ethinylestradiol warrants a trial in treating prostatic cancer.