Estrogen-progestin therapy causes a greater increase in spinal bone mineral density than estrogen therapy - a systematic review and meta-analysis of controlled trials with direct randomization.

To assess whether progesterone (P4) or osteoblast P4 receptor-acting progestin (P) contributed to estrogen (E) therapy-related increased areal bone mineral density (BMD) in randomized controlled trials (RCT) with direct randomization to estrogen (ET) or estrogen-progestin (EPT) therapy.