Tamoxifen and bones

Hi,
I was told by my GP that the Tamoxifen I am taking will also strengthen my bones.  If it blocks estrogen (which I thought was taken against osteoporosis) how can it strengthen bones?  What do you think?

[CCF-RN,MSN-JS]

Dear Ning, Tamoxifen is classified as a selective estrogen receptor modulator (SERM).  While a SERM has anti-estrogen effects on certain tissues (breast tissue), it has estrogen like effects on other target tissues such as the bones.  Clinical studies demonstrate that tamoxifen does not contribute to decreasing bone mass in postmenopausal women.  In fact, in some studies it was reported to maintain bone mineral density, which often decreases after menopause.  However there is not enough information to date on the effects of tamoxifen on bone density and this continues to be studied.

[Ernestine]

When I had a discussion about bone density with my doctor, we came to the conclusion that medical science just does not know the answer this kind of question.  We are the generation that the data for those answers will come from.  Based on my own experience with Tamoxifen, I would not be inclined to think that it would increase bone density.  I was on Tamoxifen for 8-9 months an my DEXA scan revealed that I had osteopenia.  I am 47 years old and until I started taking hormone replacement therapy for "premature menopause" I enjoyed excellent, OUTSTANDING health.  Since then I have developed cancer, been through chemotherapy and radiation, and then was told to take tamoxifen for 5 years.  After 8 months I realized I could not face another 4 years on tamoxifen.  I would proceed extremely cautiously.