Role of androgens in erectile function

Purpose: Erectile response in mammals is centrally and peripherally regulated by androgens. Severe hypogonadism in men usually results in loss of libido and potency. The present studies were designed to evaluate the possible influence of circulating androgens in the regulation of sexual function. Materials and Methods: A total of 15 men with severe hypogonadism (testosterone less than 2.0 ng/ml) were recruited. The control group consisted of 20 patients with psychogenic erectile dysfunction. All subjects underwent nocturnal penile tumescence (NPT) and rigidity monitoring during 2 consecutive nights, evaluation of cavernous artery flow using penile color duplex ultrasound (P-CDU), and real-time visually stimulated erection evaluation at baseline and after administration of 50 mg sildenafil or 3 mg apomorphine. NPT, P-CDU and visually stimulated erection were evaluated after 6 months of therapy with a 5 mg daily testosterone patch. Results: NPT analysis in subjects with severe hypogonadism showed a significant decrease in sleep related erections. P-CDU showed a partial erectile response with an alteration of the parameters analyzed, and the visually stimulated erections test was pathological. Administration of 3 mg apomorphine and 50 mg sildenafil has no influence on erectile function. Testosterone treatment for 6 months induced normalization of NPT and P-CDU parameters, and of visually stimulated erection effects with the restoration of a normal response to pharmacological stimulation with apomorphine or sildenafil. Conclusions: Our results show that testosterone has a key role in the central and peripheral modulation of erectile function even if the accurate testosterone plasma level threshold that may influence these processes remains to be established.