Hi @casstk thank you very much for sharing!

There were studies done on the circadian variations in serum CTX. According to one publication, CTX peaked in early morning hours (~5am) and reached a trough around 14:00 in the afternoon. It was not affected by 5 days of bed-rest, by absence of a normal diurnal variation in cortisol production, or by absence of a normal light cycle (blindness). Peak and trough differed in the magnitude of 80% on average.

Your 2024 baseline ctx and p1np were nice, especially with p1np at 72. However if the above observation applies, then your baseline ctx reading probably would turn out to be higher if your blood draw was earlier, say at 8am regardless of your sleeping pattern/schedule. I don't know what other members think, but I felt blood draw at 9:30am is considered late. This being said, it is important to get blood draw at consistent time for proper comparison,

How Long have you been on HRT? What dose and form of estradiol you are using? Are you on testosterone?

The relationship between serum estradiol level and bone effects (specifically on ctx) puzzles me. With a low dose 0.025mg/day transdermal E2 patch, my blood estradiol level moved only a few points to 21 from baseline 18. However, my ctx went down to 163 from 793 at end of forteo treatment. Of course discontinuing forteo had effects on ctx but still, that's a whopping change.

When your tymlos/forteo gets approval, are you planning to use it alone or with HRT as a combination? I'm very interested in hearing this aspect of planning from you. And, please share when your corrected CTX lab result is available if you could. Thank you!

my thoughts is do more research and you will find out why these markers have to be taken with a grain of salt in the short haul. My specialist only did it because I complained and wanted baselines. Then I read the research, and it is indeed unreliable by themselves. It is just a tool from year to year. Looked at over a few years. You didn't say the break between your testing.
Do a DEXA WITH A TBS SCORE a year apart and see how that looks. I can tell you my regular DEXAS were okay over 20 years with the last one saying I had come out of ostopenia even! Then I had cervical surgery and my C5 fell apart in their hands! I asked the surgeon how it could be and he explained they are standardized tests, and as well, your body bones have different density requirements. Nobody ever did a DEXA on my neck! So don't worry!