The clinical significance of bone mineral density and testosterone levels in Korean men with non-mosaic Klinefelter's syndrome.

Objective: To measure bone mineral density (BMD) and testosterone levels in patients with non-mosaic Klinefelter's syndrome (KS), as a low BMD is common in hypogonadal men, but little is known about the relationship between BMD and serum testosterone levels in men with KS.

Methods: The study included 40 patients with KS and 20 healthy fertile men recruited as controls. Serum testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were measured by radioimmunoassay. The BMD was obtained at the lumbar spine (L2-4), femoral neck and Ward's triangle, by dual-energy X-ray absorptiometry.

Results: The serum testosterone level was lower, while FSH and LH were higher, in patients with KS than in the control group (P < 0.001). Patients with KS had a significantly lower mean (sd) BMD at the lumbar spine, femoral neck and Ward's triangle, than the controls, at 0.88 (0.13) vs 1.09 (0.10) (P < 0.001), 0.78 (0.12) vs 0.87 (0.10) (P = 0.006) and 0.65 (0.12) vs 0.76 (0.11) g/cm(2) = 0.001), respectively. There was a linear correlation between all BMD values and serum testosterone levels in men with KS who had a low serum testosterone level.

Conclusions: There was a relationship between a lower BMD and testosterone levels in patients with KS. These findings suggest that low testosterone levels cause inadequate bone development and a low BMD in men with KS; therefore, testosterone replacement might be necessary to prevent bone mineral deficiency and future risk of fractures in men with KS who also have low serum testosterone levels.