Progressive Temporal Change in Serum SHBG, But Not in Serum Testosterone or Estradiol, Is Associated With Bone Loss and Incident Fractures in Older Men: The Concord Health and Ageing in Men Project

This study aimed to examine progressive temporal relationships between changes in major reproductive hormones across three waves of a cohort study of older men and (1) changes in bone mineral density (BMD) and (2) incident fractures (any, hip or non-vertebral) over an average of 6 years of follow-up. The CHAMP cohort of men aged 70 years and older were assessed at baseline (2005 to 2007, n=1705), 2-year follow-up (n=1367), and 5-year follow-up (n=958). Serum testosterone (T), dihydrotestosterone (DHT), estradiol (E2), and estrone (E1) (by liquid chromatography-tandem mass spectrometry [LC-MS/MS]), and sex hormone-binding globulin (SHBG), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) (by immunoassay) were measured at all time-points, whereas free testosterone (cFT) was calculated using a well-validated formula. Hip BMD was measured by dual-energy X-ray absorptiometry (DXA) at all three time-points, and fracture data were verified radiographically. Statistical modeling was done using general estimating equations (GEEs). For total hip BMD, univariable analyses revealed inverse associations with temporal changes in serum SHBG, FSH, and LH and positive associations for serum E1 and cFT across the three time-points. In models adjusted for multiple covariables, serum SHBG (=-0.029), FSH (=-0.065), LH (=-0.049), E1 (=0.019), and cFT (=0.033) remained significantly associated with hip BMD. However for femoral neck BMD, only FSH (=-0.048) and LH (=-0.036) remained associated in multivariable-adjusted models. Temporal change in serum SHBG, but not T, E2, or other hormonal variables, was significantly associated with any, nonvertebral or hip fracture incidence in univariable analyses. In multivariable-adjusted models, temporal increase in serum SHBG over time remained associated with any fracture (=0.060) and hip fracture (=0.041) incidence, but not nonvertebral fracture incidence. These data indicate that a progressive increase in circulating SHBG over time predicts bone loss and fracture risk in older men. Further studies are warranted to further characterize changes in circulating SHBG as a mechanism and/or biomarker of bone health during male ageing. (c) 2016 American Society for Bone and Mineral Research.