Role of Metabolic Factors in the Association Between Osteocalcin and Testosterone in Chinese Men

Objective: Osteocalcin can regulate energy metabolism and increase testosterone production. Although previous studies have shown the positive association between osteocalcin and testosterone, the effect of metabolic factors in the association is unclear. Design and Setting: Osteocalcin, testosterone, and metabolic factors were accessed in 2400 men aged 20 to 69 years, who participated in the population-based Fangchenggang Area Male Health and Examination Survey in Guangxi province of China from September 2009 to December 2009. Main Outcome Measures: Metabolic syndrome was defined based on the updated report of National Cholesterol Education Program Adult Treatment Panel III criteria. Serum total osteocalcin, total testosterone (TT), and sex hormone binding globulin (SHBG) were measured, whereas free testosterone (FT) and bioavailable testosterone (BT) were calculated based on Vermeulen's formula. The multivariable linear regression analysis was used. Results: Osteocalcin was positively associated with TT, FT, and BT in the unadjusted model (all P < .001). After adjusting for age, the positive association between osteocalcin and TT remained statistically significant (β = .17, 95% confidence interval = 0.14–0.20) and was not attenuated in each MetS subgroup including hypertriglyceridemia, hyperglycemia, elevated blood pressure, and low high-density lipoprotein cholesterol, while in the group of central obesity (waist circumstance ≥90 cm), the association appeared significantly stronger (β = 0.21, 95% confidence interval = 0.12–0.30). After further adjusting for SHBG, osteocalcin was positively associated with TT, FT, and BT in men with central obesity or men with any two MetS components (all P < .05). Conclusions: Serum total osteocalcin is positively associated with testosterone, which is probably modified by SHBG and central obesity.