Hi @triciaot I read from a few articles that the main reason behind the bone mineral density increase by bisphosphonates is due to the decreased bone resorption rate by direct inhibition of osteoclasts. As a result, "While bisphosphonates consistently increase bone mineral density, the change in bone volume, as measured from bone biopsies, is not significant in most studies [160]. The increases bone density is predominantly due to further mineralization of the bone matrix, as more water molecules are replaced by mineral [161]". This excerpt describes short term effects of bisphosphonates.

Tamoxifen ( a SERM) and estrogen are both mild to moderate antiresorptives, although estrogen has many other roles in maintaining bone health. The antiresorptive effects of either estrogen or tamoxifen might be overshadowed by a strong bisphosphonate such as reclast during concomitant use. It will be interesting to hear from your team of doctors regarding the benefits combining a bisphosphonate with tamoxifen. Please keep us updated if you could.