Chang PY, et al. - Researchers conducted a nested case-cohort study to test the premise that depending on the level of bioavailable 17β-estradiol (bioE2), 27-hydroxycholesterol (27HC) may increase fracture risk in postmenopausal women and modify the fracture risk reduction from menopausal hormone therapy (MHT). Findings suggested no association of 27HC levels alone with fracture risk. They found that 27HC and 27HC/bioE2 did not modify the fracture risk reduction from MHT. Circulating levels of 27HC relative to bioE2 might identify those at increased risk of fracture in postmenopausal women.