[Testosterone and impotence--when is androgen substitution advisable?].

Testosterone and dihydrotestosterone play a critical role during embryogenesis of the male genitalia. The development of secondary sex characteristics depends on normal circulating androgen levels. They maintain libido and sexual potency. Before testosterone supplementation men with erectile failure should receive through hormonal investigation. Testosterone is useless in the treatment of erectile problems in men with normal androgen levels. Testosterone can be administered by intramuscular, oral or transdermal routes. Transdermal systems produce serum testosterone levels closely mimicking the diurnal pattern described in healthy young men. In elderly men during long term therapy, prostate specific antigen should be measured regularly to anticipate malignant growth in the prostate.