Treatment of male hypogonadism with testosterone enanthate.

To determine the relative efficacy of several dosage regimens of testosterone enanthate in the treatment of male hypogonadism, we treated men who had primary hypogonadism with the following dosage regimens: 100 mg once a week, 200 mg every 2 weeks, 300 mg every 3 weeks, and 400 mg every 4 weeks, each for 12--16 weeks. Twenty-three men completed 37 dosage regimens. The 100-, 200-, and 300-mg dosages all suppressed the initially elevated serum LH concentrations to normal, but the 400-mg dosage did not. The 100- and 200-mg regimens suppressed the initially elevated serum FSH concentrations to normal, and the 300-mg regimen almost did not so. All four regimens produced serum testosterone concentrations that fluctuated largely within the normal range, the average concentration between doses was highest with 100 mg and lowest with 400 mg. The regimens of 200 mg every 2 weeks and 300 mg every 3 weeks appeared to be the most effective of those tested in terms of suppression of the serum LH concentration to normal and infrequency of administration. The close parallel of the FSH response to that of LH suggests that testosterone is the major physiological inhibitor of FSH as well as of LH.