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Is Anyone Else Tracking Your P1NP to CTX Ratio, While Taking Tymlos?
It is believed that the threshold to indicate bone growth can be tracked by calculating your P1NP to CTX ratio. This sure seems logical, as the rate that you are building bone versus the rate that you're losing it are key factors. To calculate your P1NP : CTX ratio, simply take your CTX and divide it by 1000 (move the decimal 3 places to the left). Then, take your P1NP and divide it my your CTX÷1000 result. If greater than or equal to 150, your building of bone is out-pacing the breakdown/reabsorption (anabolic). So again, P1NP : CTX = P1NP ÷ (CTX/1000) Result: If >= 150, then anabolic.
Are you willing to share your past and/or current results and let us know how long you've been on Tymlos. Below are results that I just calculated. I will also try to repost the link to the video that explains the relationship between P1NP and CTX (interesting theories).
Here is some interesting trending for my bone building blood markers (from pre-treatment to breaks in treatment to now).....
Trending for Bone Formation Markers (P1NP : CTX Ratio >= 150 is ANABOLIC)
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1) 08/28/25: Pre-Treatment
P1NP = 55
CTX = 492
Ratio = 112 (Losing) ❌️
2) 02/02/26: 1-Month Post-Stopping of Evenity #2 (1/2 dose)
P1NP = 52
CTX = 544
Ratio = 96 (Losing) ❌️
3) 05/04/26: Tymlos (3 wks @ full dose + 3 wks @ 1/2 to 3/4 dose)
P1NP = 128
CTX = 707
Ratio = 181 (Building) ✅️
Video - Scroll down in this linked post to find the video (hope this linking works): https://connect.mayoclinic.org/comment/1558097/
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I have been keeping track of 40 mcg Tymlos for over 2 years. You may find this interesting according to @cathyf31's ratio where 150 or better is gaining bone. CTX is divided by 1000. As you can see, all of my blood tests showed over 150, except for 6 months of 40 mcg Tymlos and when I discontinued Tymlos. A half dose of Tymlos worked well for me.
12/23 on 20 mcg Tymlos for one month 78/519=150
5/24 on 40 mcg Tymlos for 3 months 190/1401=136
8/24 on 40 mcg Tymlos for 6 months 310/1414=219
12/24 on 20 mcg Forteo for 3 weeks 190/1238=153
5/25 on 20 mcg Forteo for 6 months 179/912=196
10/25 on 40 mcg Tymlos 5 months since stopped Forteo
and 2 months on 14 mcg Estrogen patch 147/654=224
2/26 on .14 Estrogen patch for 6 months, no Tymlos 38/371=102
I just had my blood drawn again and am waiting for results. I went back on 40 mcg Tymlos for a month and increased my Estrogen patch to 25 mcg for 2 months. I had a very good DEXA a year ago and will be having another DEXA scan next week.
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3 ReactionsOpps. The only time on 40 mcg Tymlos with a low ration was at 3 months.
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1 Reaction@drsuefowler
May I ask what led you to change your estradiol patch dose? Would love to see your new set of BTM results when they become available, if you could share. Thanks
@mayblin, I wasn't happy with my bone marker results on 2/26. I raised the Estrogen to hopefully lower the CTX. I saw that the ratio on 2/26 was worse than my first bone marker blood test on 12/23. I didn't think that 20 mcg Tymlos then for one month would have done anything. If that was true, then my bone markers were good without medication. Since I had had several fractures, maybe the super low dose of Tymlos had done something? We'll never know.
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1 Reaction@drsuefowler Interesting. Why were you starting and stopping the Tymlos? Were you struggling with side effects?
@cathyf31, yes I could only tolerate a half dose. I saw a new endocrinologist who prescribed Forteo. I was on that for 6 months with fewer side effects, except I didn't like the brain fog. My mother had dementia and I don't want to get that. Then I went back to a half dose of Tymlos. I stopped it after 2 years, since that is all that's allowed. I wasn't happy with my bone markers, so started it again. I am hoping to keep my gains with Estrogen. My old endocrinologist wants me on a partial dose of Reclast. It all depends on the results of my blood test and upcoming DEXA.
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1 Reaction@drsuefowler I believe that's the first time I've seen any mention of a partial dose of Reclast. That gives me hope for an option with that, if I experience significant side effects like I have with my other attempted osteoporosis medications. I haven't even completed two full months yet of Tymlos, but Reclast is the plan after the end of the 2-year max on Tymlos. Best wishes to you!
Good luck with your osteoporosis journey @cathyf31.
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1 ReactionHi everyone! I got my next CTX score after a year (I am in my second year now) with having had one Reclast in Aug. 2023 and in second year of Tymlos. My CTX dropped 50%, which is excellent news. I will have my DEXA this summer. I went to injecting only in the stomach which I hope will bring me better returns than my first DEXA which was a disappointment. So this is nice news. I don't know what happened to the P1NP test... that was supposed to have been done. But here are the numbers. @gently and @mayblin who wanted to stay in the loop.
May 14, 2026 131pg/mL
Aug 19, 2025 338pg/mL
May 6, 2025 643pg/mL (I don't think this is correct, I will look into it)
Aug 16, 2024 366pg/mL
Jun 14, 2024 322pg/mL+
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2 Reactions@drsuefowler I am confused. Is the first number the ratio? If Tymlos had you all the way to 310 after 10 months why did you stop and switch to Forteo?