Low serum free testosterone level is associated with carotid intima-media thickness in middle-aged Japanese men

In the present study, we measured carotid artery intima-media thickness (CIMT) and assessed several metabolic factors in middle-aged healthy Japanese men to clarify the relation between testosterone and atherosclerosis. The study comprised 176 male employees aged ≥40 years who visited Osaka University Healthcare Center for their annual health examinations. Serum total testosterone (TT) concentration was measured using radioimmunoassay (RIA) and serum free testosterone concentration was measured using analog ligand RIA (aFT). A multivariate model adjusted for age, body mass index, mean arterial pressure and treatment for hypertension demonstrated a significant association between aFT and CIMT. Even after adjustment for other clinically relevant factors, the significant association between aFT and CIMT was not attenuated. After adjustment for all other clinically relevant factors, both univariate and multivariate models ascertained the stepwise association that a level of aFT of ≤10.0 pg/mL was significantly associated with CIMT. However, the association between TT and CIMT was not significant in either univariate or multivariate models. We conclude that our finding showing that low serum aFT level is an influencing and independent risk factor for CIMT is of value in the clinical setting because no other studies, to our knowledge, have conducted multivariate analyses using the various metabolic factors included in the present analyses.