[Association of nocturnal penile rigidity with testosterone, metabolic syndrome, and other variables: a prospective...

The aim was to study whether nocturnal penile rigidity (NPTR) correlates with metabolic syndrome (MetS) and testosterone in men consulting for erectile dysfunction (ED).

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.

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).

Testosterone levels are weakly associated with penile rigidity and disappear when associated with MetS.