[Original article] Serum testosterone is correlated with higher bone mineral density in the low serum 25-hydroxyvitamin D concentration among healthy middle-aged and older Korean men

Background: Serum testosterone and 25-hydroxyvitamin D [25(OH)D] have important roles in the maintenance of bone mineral density (BMD). We compared the BMD according to the serum testosterone with serum 25(OH)D concentration. Methods: A total of 414 subjects of middle-aged males were selected with the data of serum testosterone, 25(OH)D, and BMD by Dual-Energy-X ray-Absorptiometry. Before comparing the femur neck BMD (FNBMD), total hip BMD (THBMD), and lumbar spine BMD (LSBMD), the 25(OH)D was divided into two groups by the median concentration (37.5 nmol/L). In addition, the serum testosterone was also divided into three groups with tertile. Each BMD was compared, according to the groups of serum 25(OH)D and testosterone, by relevant variables adjustment. Results: Serum testosterone and each BMD showed positive correlations in the low 25(OH)D concentration (<37.5 nmol/L). In addition, LSBMD was significantly higher in the top tertile of serum testosterone with the low 25(OH)D concentration (<37.5 nmol/L). The odds of having the highest tertile of FNBMD and THBMD in the top tertile of serum testosterone were 2.75 (95% confidence interval [CI]; 1.11-6.85) and 2.76 (95% CI; 1.09-6.96), respectively, whereas, in the LSBND, the significant odds ratio being in the 2nd tertile of serum testosterone (OR=4.02, 95% CI; 1.69-9.54), not in the highest tertile. Conclusion: Serum testosterone was significantly correlated to BMD in the lower concentration of 25(OH)D (<37.5 nmol/L), which may mean that the maintenance of serum testosterone concentration is important, at least in the lower serum 25(OH)D concentration to keep relatively higher BMD in the middle-aged males.