Spironolactone and ketoconazole block the synthesis of androgen, and spironolactone and cimetidine interfere with androgen action by competing with androgen for binding to the androgen receptor. Testosterone may be low and oestradiol may be high in abusers of marijuana, heroin, or methadone, although the exact reasons are unclear. Alcohol can cause plasma testosterone levels to fall, independent of liver disease or malnutrition. Antineoplastic and chemotherapeutic agents can impair spermatogenesis. Cyclophosphamide causes azoospermia or oligospermia within a few weeks after the initiation of therapy. Combination chemotherapy for acute leukaemia, Hodgkin's disease, and other malignancies may also impair Leydig cell function.
