The relationship between sex steroids, bone turnover and vertebral fracture prevalence in asymptomatic men

Abstract

To examine the association between oestradiol (E2), testosterone (T), SHBG levels and vertebral fractures' (VFs) prevalence in asymptomatic men. The study cohort consists of a population of 112 consecutive men (mean±SD (range) age, weight and BMI were 62.9±9.2 (41-84) years, 75.0±13.8 (45-120) kgs and 26.4±4.7 (18.0-39.6) kg/m(2), respectively). Lateral vertebral fracture assessment (VFA) images and scans of the lumbar spine and proximal femur were obtained using a GE Healthcare Lunar Prodigy densitometer. VFs were defined using a combination of Genant semiquantitative approach and morphometry. Serum levels of T, E2, CTx and osteocalcine were measured. Free androgen index (FAI) and free estradiol index (FEI) were calculated respectively from the ratio of serum T and E2 to SHBG. Among the 112 men, 38 (33.9%) had densitometric osteoporosis, and on VFA, VFs were identified in 60 (53.5%): 24 men had grade 1 and 36 had grade 2 or 3 VFs (32.1%). Men with VFs weighted less and had a statistically significant lower lumbar spine and total hip BMD and T-scores than those without a VFA-identified vertebral fracture. Levels of osteocalcine, CTx, and SHBG were statistically higher in men with grades 2 and 3 VFs than men with grade 1 VFs and those without VFs whereas FAI and FEI levels were significantly lower. Comparison of patients according to quartiles of SHBG levels showed that men in the highest quartile were older, had a lower lumbar spine and total hip BMD and a higher prevalence of osteoporosis and VFs. They had also higher levels of CTx. Stepwise regression analysis showed that the osteoporotic status and SHBG was independently associated to the presence of VFs. Men with asymptomatic densitometric VFs have lower BMD than subjects without VFs. They have evidence of higher SHBG levels and hence lower free sex steroids as well as increased bone resorption. This study confirms that BMD and CTx are the most important determinant of asymptomatic VFs, and that SHBG is an independent risk factor that must be taken into account.