Characteristics of studies included in the meta-analysis.

RR, relative risk; CI, confidence interval; DR, dose-response; HB, hospital-based; NA, not applicable; RIA, radioimmunoassay; BMI, body mass index; pre, premenopause; post, postmenopause; HRT, hormone replacement therapy; PB, population-based; ELISA, enzyme-linked immunosorbent assay; EPIC, European Prospective Investigation into Cancer and Nutrition cohort study; NHS, Nurses’ Health Study; FIT, the Fracture Intervention Trial; HOMA-IR, the homeostasis model assessment of insulin resistance; QUICKI, quantitative insulin sensitivity check index; PLCO, Prostate, Lung, Colorectal and Ovarian cancer screening trial. Characteristics of studies included in the meta-analysis.