Testosterone maintained suppression of both serum FSH and LH to near intact control levels at a dosage approximating the "physiological dosage range," although LH was suppressed by a lower dose than was FSH. 5-Dihydrotestosterone and 3-androstanediol could suppress serum LH only at the "physiological dosage range"; serum FSH suppression appeared at higher doses. Fluoxymesterone, an orally active androgenic drug, could suppress neither serum FSH nor LH to control levels within the "physiological dosage range." 3-Androstanediol was ineffective over a dose range of 30-2000 µg/kg/day body wt with respect to stimulation of accessory organ weights and to gonadotropin suppression.

Seminal vesicle weights were considerably heavier in testosterone-treated animals than in those administered 5-dihydrotestosterone, 3-androstanediol, or fluoxymesterone on a dose-for-dose basis, while ventral prostate weights were similar for all four steroids. A dosage of estradiol equal to 0.3% of the suppressive testosterone dose suppressed both serum FSH and LH, and significantly stimulated seminal vesicle weight; estradiol treatment was equally effective for serum FSH and LH suppression.

Results indicated that (1) the physiological activity of androgens, as judged by their effects on accessory organs, does not correlate well with the suppression of gonadotropins; (2) testicular steroid secretion can account for the suppressed levels of gonadotropins seen at age 26 days, but (3) metabolism of these steroids is probably necessary for suppressive action, in view of the incomplete results with fluoxymesterone; (4) metabolism of testosterone to estrogen may in part be necessary for complete FSH control; (5) the further reduction of 5-dihydrotestosterone to 3-androstanediol does not change its biological activity, while conversion to 3-androstanediol destroys activity.