Hi esb13,

Both the CTx and the P1NP tests need to be conducted simultaneously for their ratio to provide meaningful information. This ratio provides a snapshot in time and is crucial for accurate assessment.

I'm not at all surprised that your Endo believes the CTx is unreliable. CTx is particularly sensitive to certain factors. It will only give useful results if done correctly. For optimal accuracy, it's essential not to take collagen or biotin supplements for 48 hours prior to the test. Additionally, fasting overnight and scheduling the test first thing in the morning (preferably before 8:30 am) are recommended. Ensuring consistency in the timing of each test is also important.

Your Endo also said to just follow the P1NP numbers. It's true that if this number goes up, as it should on Tymlos, you're more likely than not growing bone, or at least slowing down loss. Some people, for whatever reason don't respond well to treatment. In some cases, their CTx may still be very high. I prefer to have as much data as possible to track my treatment success. Knowing both the CTx and the P1NP, I can calculate the bone turnover ratio, and that's reassuring for me.

I'll put the equation I use, and a sample calculation to find the 10 to 1 ratio below. If you choose to have both tests done together in the future, I hope you'll find it useful.

Using the values from @babbsjoy's earlier input:
CTx = 231
P1NP = 41

The equation for the ratio is CTx/P1NP = 10/x.

Sample calculation:
231/41 = 10/x
10 ÷ (231/41) = x
10/5.63 = 1.77
x = 1.77

I hope that Tymlos works well for you. If my numbers weren't so bad, and I hadn't had a compression fracture, I would have opted for that before Evenity. Best of luck.