Another proposed mechanism is that vitamin D analogs induce ER transcription. This has been reported in the JK 1624F2-2 (JFK) analog in pre- and post-menopausal women’s bone cells [65]. The synergistic effect of 1,25(OH)2D and 17β-estradiol increased osteoblastic MC3T3-E1 cell proliferation and viability [67]. Post-menopausal women receiving HRT and low amounts of vitamin D + Ca supplements (300 IU vitamin D + 93 mg Ca/day), but not those receiving HRT only, for 4 years had higher BMD compared to controls that did not receive HRT, vitamin D, nor Ca [68].