Association of nocturnal penile rigidity with testosterone, metabolic syndrome, and other variables: A prospective cross-sectional pilot study

Introduction: The aim was to study whether nocturnal penile rigidity (NPTR) correlates with metabolic syndrome (MetS) and testosterone in men consulting for erectile dysfunction (ED). Material and methods: 234 men were included in a prospective, cross-sectional pilot study. Serum total and bioavailable testosterone and other biochemical constituents were measured and compared with NPTR. Patients were classified by normal or low/abnormal penile rigidity (abnormal meaning predominant organic component of ED) and presence or absence of MetS to test the hypothesized correlations. Results: Application of the logistic regression model to rigidity as the dependent variable showed the risk of low penile rigidity to be significantly lower for patients with higher total (OR = 0.96, 95% CI = 0.92-0.99) or bioavailable testosterone (OR = 0.91, 95% CI = 0.84-0.99). Patients with testosterone levels between 8 and 12 mmol/L had a quadrupled risk of low penile rigidity compared with patients with higher levels (>12 mmol/L) (OR = 3.96, 95% CI = 1.89-8.31). Considering men without MetS, age and body mass index were associated as significant factors for low penile rigidity: age increased risk by 8% (OR = 1.08, 95% CI = 1.03-1.13) and BMI increased it by 18% (OR = 1.18, 95% CI = 1.01-1.38). Conclusion: Testosterone levels are weakly associated with penile rigidity and disappear when associated with MetS. © 2011 AEU. Published by Elsevier España, S.L. All rights reserved.