Sex hormone-binding globulin levels positively linked to cortical bone size in men

There is a positive association between sex hormone-binding globulin levels and cortical bone size in healthy adult men — independent of sex steroid levels — new data suggest.

The cross-sectional, population-based study included 677 male siblings aged 25 to 45 years. Researchers measured areal bone parameters using DEXA, cortical bone parameters using peripheral quantitative CT, and serum testosterone, estradiol and sex hormone-binding globulin (SHGB) levels using immunoassays.

According to the results, regression models that included age, height and weight revealed that SHBG levels were positively associated with hip and whole bone area, but not areal bone mineral density. Cortical bone area and periosteal and endosteal circumferences at the tibia and radius were also associated with higher SHBG levels.

The associations persisted after the researchers adjusted for sex steroid levels.

However, the researchers reported a negative association between SHBG levels and trabecular volumetric BMD. Further, there was no association between SHBG levels and cortical volumetric BMD or cortical thickness.

“This study demonstrated that higher serum SHBG levels are independently associated with a larger cortical bone size and thus more favorable indices of bone strength in healthy men at the age of peak bone mass, which seems in contrast with observations in elderly men and men with idiopathic osteoporosis,” the researchers wrote, adding that the effects of SHBG may be driven by the influence on sex steroid levels; however, other mechanisms must be considered.

Vanbillemont G. J Clin Endocrinol Metab. 2010;95:1579–1586.