It’s funny you ask, @gently. When I got my very first result of bone turnover marker back, which showed P1NP 400 at 13 mo of forteo, I had my doubts already. Looking at the reference range of 20-108mcg/L for 46-60yo female, my raw reaction at that moment is what the _!? Dr. Internet doesn’t help either: severe liver disease, even malignancy could be the culprit. When the rational mind took over, I realized that I had a huge anabolic response to forteo! Bone turnover markers offer more than a glimpse to bone formation vs resorption than we thought. The dynamics of two markers are in tandem. Although the markers are still not prefect in predicting or directing clinical decisions in all patients’ cases, I personally have more confidence in them and my serial tests since then showed. Instead blindly ‘walking’ towards the target, i.e., end of therapy or the annual/biannual Dexa scan, I definitely would like to see how those markers changes during therapy, especially during anabolic therapy, for future reference should repeated anabolic treatment occur.

Many factors affect bone markers results, as discussed in this thread:
https://connect.mayoclinic.org/comment/1052882/
Besides the factors mentioned above, doubts for bone turnover markers could also stem from many other reasons. The assays themselves have storage requirements. Sensitivities among different assays differ also so we’d want to stick with one lab. People who have severe liver diseases, end stage kidney diseases and some particular malignancies, etc. could throw results off, either up or down. I’m sure researchers on the front line are working on those issues. We as patients shouldn’t be easily backed off just by the non-believers. Science advances faster if we all be part of the process.

Are you a doubter or a believer, @ gently?