Androgens and penile erection: evidence for a direct relationship between free testosterone and cavernous vasodilation in men with erectile dysfunction

OBJECTIVE Androgens are essential in the maintenance of nitric oxide-mediat ed erectile activity in the rat. The objective of the present study was to investigate the role of androgens in regulating trabecular smooth muscle re laxation in the corpus cavernosum in response to vasoactive challenge in me n with erectile dysfunction (ED). DESIGN Retrospective, double-blind correlation analyses. PATIENTS Fifty-two impotent patients without confounding risk factors for E D were obtained from a total of 250 undergoing diagnostic evaluation. MEASUREMENTS All patients had dynamic colour duplex ultrasound (D-CDU) and hormonal evaluation for LH, total and free testosterone, SHBG and oestradio l. RESULTS Based upon D-CDU results patients were diagnosed as having arteriog enic (AR, n = 18; mean age 51) or corporeal venocclusive (CVO, n = 13; mean age 49) ED; in other patients (n = 21, mean age 43) a diagnosis of psychog enic (P)-ED was made by comprehensive psychogenic testing and confirmed by normal D-CDU results. AR and CVO patients had altered compliance of caverno us arteries recorded by D-CDU [20-25% lower resistive index (RI) than patie nts with psychogenic ED], and lower free testosterone (FT) levels than psyc hogenic patients [42.3 +/- 3.5 SE and 49.3 +/- 5.2 vs. 75.2 +/- 7.6 pmol/l, respectively; P < 0.01]. More important, in all patients there was a stron g direct correlation between resistive index values and FT levels (r = 0.47 , P = 0.002); the relationship was maintained also when adjusted for age, S HBG and oestradiol (r = 0.37, P = 0.02). CONCLUSIONS These results indicate that in men with erectile dysfuntion low free testosterone may correlate independently of age with the impaired rel axation of cavernous endothelial and corporeal smooth muscle cells to a vas oactive challenge. These findings give clinical support to the experimental knowledge of the importance of androgens in regulating smooth muscle funct ion in the penis.