Background: Although studies have demonstrated the suppression of norm
al gonadal function in the experimental setting, the specific mechanis
ms by which androgenic-anabolic steroids impact male gonadal function
remain ill defined, Methods: Following 2 consecutive weekly injections
of an identically appearing testosterone cypionate (TC) placebo, subj
ects were randomized to a TC dose of 100 mg/wk, 250 mg/wk, or 500 mg/w
k, Following the last weekly injection of active agent the subjects re
ceived 12 consecutive weeks of TC placebo injections, Results: Spermat
ogenesis was impaired by each of the doses of TC employed in this stud
y, but the observed decreases in sperm count were neither strictly dos
e dependent nor consistent between individuals treated with the same d
ose, Basal leuteinizing homone (LH) and follicle stimulating hormone (
FSH) became undetectable 2 weeks after the start of 250 and 500 mg/wk
TC injections and were lost within 5 to 6 weeks of starting 100 mg dos
es, Pituitary gonadotropin responses to leutinizing homone releasing h
omone (LHRH) disappeared more slowly with FSH responses being lost 1 t
o 3 weeks after the loss of basal FSH activity, Leuteinizing hormone r
esponses to LHRH appeared to be suppressed last, disappearing 4 to 6 w
eeks after FSH responses to LHRH. Conclusions: Exogenous testosterone-
mediated inhibitory influences on the hypothalamic-pituitary-testicula
r axis were reversed following the cessation of drug treatment.