The role of androgens in the erectile response: A 1999 perspective

Evidence from several laboratories strongly supports a critical role for androgens in the maintenance of the mammalian erectile response. In animal studies, androgens appear to act at the end-organ level (i.e., corporal tissue and vasculature), as well as in the portions of the nervous system which mediate erection. Particularly in the rat model, androgens act centrally to support copulatory behavior and peripherally to maintain the production of nitric oxide and support the veno-occlusive mechanisms. Other studies suggest that alternative, non-NO-dependent, pathways may also be androgen sensitive. However, despite this expanding knowledge base about how androgens act in the erectile response in laboratory animals, the recent studies have not greatly clarified the role of androgens in human penile erection. There does not seem to be a strong cause and effect relation between blood androgen concentrations and erectile function; even in severely hypogonadal men, the erectile response is not always lost, and testosterone treatment of hypogonadal men with erectile dysfunction does not necessarily restore lost erectile function. In addition, different types of erection (nocturnal, in response to visual sexual stimulation, in response to sexual partner) may require different degrees of androgenic support.