Sex hormones are negatively associated with vertebral bone marrow fat

Context Higher bone marrow fat (BMF) ¹ is associated with osteoporosis and reduced hematopoiesis. Exogenous estradiol reduces BMF in older women, but effects of endogenous sex hormones are unknown. Objective To determine if endogenous sex hormones are associated with BMF in older men and women. Design, setting and participants Cross-sectional study in the Age Gene/Environment Susceptibility (AGES) Reykjavik cohort. Participants using medications that may affect BMF were excluded. Main outcome measures Vertebral BMF was measured with magnetic resonance spectroscopy. Estradiol, testosterone and sex hormone binding globulin were measured on archived serum. Linear regression models were adjusted for age, total percent body fat and visit window. Results Analyses included 244 men and 226 women, mean age 81.5 (SD 4.1) years. Mean BMF was 54.1% (SD 8.6) (men) and 54.7% (SD 8.1) (women). In adjusted models, per 1 pg/ml increase in total estradiol, there was a statistically significant 0.26% decrease in BMF in men (95% CI: − 0.41, − 0.11) and a non-significant 0.20% decrease in women (95% CI: − 0.55, 0.15), with no evidence of interaction by gender (p = 0.88). Per 10 ng/dl increase in total testosterone, there was a significant 0.10% decrease in BMF in men (95% CI: − 0.17, − 0.03) and a non-significant 0.13% (95% CI: − 0.79, 0.53) decrease in women, with no evidence of interaction by gender (p = 0.97). Conclusion Higher bone marrow fat is associated with lower total estradiol and testosterone levels in older men, with a similar but statistically non-significant association in older women. Sex hormone levels appear to play a role in the regulation of bone marrow fat in older adults.