@ripley I think the statement made by the endo you saw recently was correct and incorrect at the same time. S/he is right since for the majority of people, CTX or P1NP will fall in the "normal" range with rare exceptions. However, if we look at the two bone markers in reference with each other, the picture could be totally different. For example, for two different persons having a same P1NP reading of 50, the person with a high CTX in 600s will be considered an abnormal high turnoverer resulting bone loss, when compared with the other person with a CTX in 300s. After many readings, I think for a treatment naive person, ideally it's best to have multiple baseline btms done in a span of 6-12 months. Then using the average of the readings as a true baseline to "smooth" out variability. If, the anuual dexa scan shows bone loss, then you'd know you are losing bone with this baseline of btms. It's evident that the variability exists among individuals especially with the interference of different medical conditions. This might be the root for the difficulties in interpreting btms. I'm anthusiastic in using btms as a tool and convinced my endo ordering them periodically. Unforturenately btms have not incorporated in original accessement nor in treatment monitoring as a routine, although they were actively used in many clinical trials.