I am going to preface my remarks with a reminder of the topic of conversation. Which is deciding to take endocrine therapy or not. I have been reading your posts and the great test information posted by @windyshores to that end. I also think there is naturally an imbalance of people posting that have side effects, most of the people who post on a topic are not the ones who are doing great,.
Yes, endocrine therapy can increase bone density loss, especially in those who are already losing bone density and those who are sedentary.
Every persons situation is different, every persons cancer is different. Every persons response to endocrine therapy will be different as well.
All of us have to be as informed as possible, and then make our own cost vs. benefit analysis, and then navigate our own path. Things like bone structure, age, previous illness, supplements, aggressiveness of cancer all have to be considered and are not something you can know by reading a blanket guideline, nor can you know these things about someone you have never met. Add in that everyone else has different wants, likes, and goals, or fear of recurrence and you get something deeply personal. A test cannot answer these things.
I did take 5 years of Tamoxifen and more than 5 years of Anastrazole, almost 18 years from initial diagnosis, I do have some substantial bone loss in my spine but none in my hips. I have taken some bone strengtheners before the pandemic started, but have not been able to resume them since. I currently have stable metastatic breast cancer, and I never have to second guess if I did everything within my power to prevent it. For me it was the right choice. I like to say it hasn’t always been easy but I am still here to complain about it.