P1NP and CTX results

Sorry, I made a more readable chart. When I put it on the website, it filled in all the spaces.

You can take Forteo every other day. I do that and have had bone density increase in 8 months.

That's wonderful @cs53. Thanks for posting.

This may not be the right place to ask but wondering if CTX and NTX can be too low? Just got blood work done (on Fosamax about 9 months; after most recent (slightly improved) DEXA he wants me to go on Reclast (once a year infusion). I read much about marker testing on this site and kind of pushed for it. Both CTX NTX numbers came out quite low. PN1P I have not done nor been offered. Have appointments lined up with multiple doctors who treat osteoporosis starting in a couple of weeks but would like some information in the meantime if possible. Not seeing much on the internet.

CTX is a very sensitive test. The number can change based on the time of day. P1NP is maybe the more important indicator of whether the bone medication is working.

@drsuefowler, I looked it up: for P1NP testing, the coefficient variation (CV) is reported to be around 1-3% for intra-run (within a single assay run), and typically around 3-6% for inter-run (different assay runs), depending on the assay type. For your recent P1NP readings, CV ~8.9% is a bit high regardless whether the tests were in a single run or not, or what type of assay it was. However, this may not matter since both P1NP readings are very much elevated - there is no doubt you are responding to either tymlos or forteo.

The trickier question to answer is whether or not these markers are indicating that the meds are helping building bones, given your high CTX. I’ve thought about the exact problem for a while and did some reading as I had similar bone marker pattern during Forteo treatment. You see, at 13mo Forteo my P1NP was in the 400s with no CTX measured (won’t be surprised it was in the 1000s if tested). By 17mo, the readings were 200, 910 for P1NP and CTX. This would result in a similar ratio as yours currently. My bmd improvement was about 5% for lumbar during first year and 2 to 8% for all sites in second year. I have been wondering if my high turnover during Forteo affected the results especially for the first year. But it is very hard to determine as I had Covid twice and did not adhere a bone-healthy diet during first year. Literatures didn’t really offer too much info regarding the correlation between high/low turnover during PTH analog therapy and bmd improvements. It is hard to make a decision in your position. Good luck and look forward to hearing your progress in the future.

@cs53, with every other day dosing of Forteo, do you use all the doses in a pen so one pen lasts you about 2 months or do you discard the pen after 28 days following the initial dose like the manufacturer recommends (but you’d lose 1/2 of the meds in a pen)?

I was discussing with my endo about every other day dosing in the future. If you don’t mind sharing, what’s your bmd % improvements, or T score improvements? This will be very useful information. Thanks!

I went from -3.5 to -2.9 in 8 mos

I don't use the pen for 2 months, but I do use for about 35 days. It seems like such a waste to throw something half out, it is so expensive. It is refrigerated, it is chemicals, not a biologic - and I can't get an answer how diluted or unsafe it becomes. I read some people use it longer so I have pushed the envelop slightly. I now have Medicare so there is a max OOP for the year, so I don't feel as bad wasting some to get the full effect . Before it cost me $800 a month and I got some free samples from my doctor which helped. See if your doc can give you some free samples to at least try.

@mayblin, those are very good results. I'm glad to hear that I am not the only one who has a high CTX on Forteo. I'm hoping to get the good results that you achieved. The coefficient variation percentages are interesting.

My concern about Forteo is the REMS Echolight test results. On 5/27/24, my spine showed -3.1. I was excited when on 12/12/24, it showed -2.8 after 9 months of Tymlos and 3 weeks of Forteo. Recently, on 4/29/25 it was back up to -3.0 after 5 months of Forteo. I don't know if this is significant, but it is upsetting.

My right femur BMD improved from -3.4 on 5/27/24, to -3.3 on 12/12/24, to -3.0 on 4/29/25. At the same time, my fragility score worsened from 46.1 to 48.8 to 52.8/100. Likewise, my five year risk score worsened from 30-50 to over 50/1000. I thought these medications were supposed to help trabecular bone more than cortical bone, but this is the opposite. I wonder if my exercise has helped my right femur BMD and my osteoclasts have been busy?

Thanks for input as always @mayblin.