Hi @nme1985 in post menopausal women, the CTX ‘normal’ range is very wide. Depending on the lab you are using or which method of testing that the lab is using, the range could also vary a little bit. Generally CTX falls 104-1008pg/ml +/-variation of lab/testing method. Stick with one lab is best.

In hormone therapy, estrogen is mainly used for its antiresorptive function, although it has many other wonderful effects on the bone. Hence the CTX could be monitored for therapy along with yearly Dexa scan. If you are taking testosterone, get P1NP level at the same time you test for CTX is a good idea. Your current CTX level is looking great!

nme 1985,
ctx measures a fragment of collagen that is removed by the bloodstream when the bones are being broken down. It is higher if you are healing a broken bone or if your bones are still growing Or if you have osteoporosis. 880 reflects greater bone breakdown than 350. Which is great if you've fractured or if your bones are growing.
Even so, if the P1NP is high you might still be replacing the bone equal or greater than the bone you are losing.
Bone turnover, though, is important (in addition to growing bone and healing bone) for remodeling bone. You need different bone alignment and strength for variant activities. So if you were to take up parachuting, your bones would breakdown and rebuild to proctect you from breakage in this activity.
Do you really have ten years of CTX. It would be interesting to look at in terms of age and bisphosphonate use, if you feel like entering them here.