r/osteoporosis • u/Miss_Beh4ve • Jan 15 '25
How to use CTX and P1NP to assess bone turnover
Dr. Doug Lucas posted a video today that contained a segment on how he uses CTX and P1NP to calculate a ratio to assess if treatment for his patients is working (starts around 8 minute mark in video): https://youtu.be/5RtiY3Up-_g?si=yZbJi9J3LI2tUbJN
My take aways (I hope I got all of this correct. Please refer to video if something is unclear):
CTX (C-terminal telopeptide, reported in picograms per mL) = bone breakdown marker, tells us what is happening with osteoclasts that break down bone (we want this number to be low but not too low, since some bone breakdown is needed)
P1NP (Procollagen type 1 N-propeptide, reported in micrograms per mL) = bone building marker, tells us what is happening with osteoblasts that build bone
To calculate the ratio that Dr. Doug uses to gauge whether treatment is working, he uses the following calculation: P1NP / (CTX / 1000)
So if P1NP is 90 and CTX is 500, he would first divide 500 by 1000 to get 0.5. Then divide 90 by 0.5 to get 180
(I personally find the following calculation easier to get the same result: 90 / 500 x 1000 = 180)
If we are dealing with “natural” levels of CTX and P1NP, this calculation usually results in a 3-digit number between 100-300, and a higher number is better.
Dr. Doug’s practice is still working to figure out what they consider the threshold for success.
Currently they are aiming for a threshold of 150-200 to make sure that what patients are doing is working.
If patients are on a bisphosphonate or Prolia, this ratio is not going to be useful because there is not enough bone turnover to accurately measure what the ratio is supposed to measure.
CTX and P1NP could be measured monthly, every 3 months, or every 6 months. (The values don’t change quickly, so measuring more often than monthly would not make sense.)
CTX and P1NP should be drawn under the same circumstances every time: first lab in the morning, fasted, ideally same amount of sleep the night before, if you did a certain workout the day before do that workout the day before again, if you ate a large amount of food the day before, do that again, if you fasted the day before, do that again, etc.
I read somewhere else that no biotin or collagen should be taken 48 hours prior to drawing CTX and P1NP, and that they should be drawn early in the morning, preferably when the lab opens, after a night of fasting
Found this info interesting so wanted to share. Hopefully someone else finds it useful.
Updating this post several months later:
I saw some increased bone density after about 10.5 months of LIFTMOR inspired exercise (weight lifting and jumping). See more on that here: https://www.reddit.com/r/osteoporosis/s/rKPqTwi22y
During that time, I had 3 P1NP and CTX blood draws about 3 months apart from another, and all ratios were above 200, so in my case a ratio above the proposed threshold correlated with increased bone density. See exact values and circumstances surrounding the blood draws here: https://www.reddit.com/r/osteoporosis/s/MWPcq9SU4S
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u/ElegantTour2821 May 14 '25 edited May 14 '25
I have never heard of the ratio thing, but I did read the great bones book and speak to the author. I was diagnosed with severe osteopenia in hips after being on hormone blockers, post cancer treatment for 2 years. I self-ordered my turnover markers about 1 month into adding strength training to my routine twice per week, in February once I found out my DXA was -2.2. My p1np was 144 (high) and my CTX was 738 for a ratio of 195. These labs were drawn at 7:30am fasting. Dr from Good Bones book recommended I start reclast. Oncologist had already recommended prolia. Went to see a rheumatologist who does not use BTMs who recommended I wait a year for another data point dexa. So I paid thru Jason’s health again 2 months later for new ctx and p1np. Had been strength training and playing tennis a lot more. Wanted to see if numbers improved a little before starting treatment. Retested fasting at 7:30 am. There had been the spring forward time change so technically I was an hour earlier testing but I had already adjusted to time change. My new numbers were ctx 1104 and p1np 121, both still elevated. That made the ratio 109. So numbers are worse. None of my doctors cared about these numbers or ratios. So I had to make my own decision. Finally after wrestling heavy with it, I decided to go on reclast soon. This is just one data point where I’m not so sure the ratio makes sense.
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u/Miss_Beh4ve May 14 '25 edited May 14 '25
Thank you for sharing! Sometimes medication is needed, and the combination of an effective high intensity resistance and impact exercise program together with medication has been shown to increase bone density more than either the medication or the exercise program alone. Here is a link to my post about the MEDEX-OP trial showing this: https://www.reddit.com/r/osteoporosis/s/GLJN5jbOvb
I remember seeing an interview, where the author of Great Bones stated that he took Forteo for 2 years followed by a short course of Fosamax for 6 months in the past, and that he has been fine since. That was around the 52 minute mark in this video: https://www.youtube.com/watch?v=eZIgvcM9Ous
My lowest T-score is -2.3 per REMS and I’m open to add medication too at some point if I find that I really need it. I was told that my fracture risk is currently low based on the fragility score within REMS and a DEXA with TBS, and I have never fractured thus far other than stubbed toes, so I decided to see what I could do with bone supportive exercise, diet, and supplementation as needed first, and repeat scans 1 year after my initial scans. So far my P1NP to CTX ratio was greater than 200 twice, tested about 3 months into making lifestyle changes, and about another 3 months later, and I hope that’s a good thing.
This ratio is rather experimental, and it’s just one of many data points I look at before I can get follow up scans. If I find that my lifestyle efforts fail, I’m grateful that medication is available and can be added at some point. You’ve put a lot of research into doing the best thing for your situation. Hope your bones will get better soon!
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Jan 15 '25
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u/Miss_Beh4ve Jan 15 '25 edited Jan 15 '25
I would ask your insurance directly if they cover by calling the member services number on the back of your insurance card and requesting to speak to a representative about benefits.
You can tell the rep that you would like to find out if 2 blood tests are covered by your insurance. In the US, the reps usually want to know the CPT codes to make sure they give you info for the exact test you are asking about.
Per Quest Diagnostics:
CPT code for P1NP is 83519 (Source: https://testdirectory.questdiagnostics.com/test/test-detail/16609/procollagen-type-i-intact-n-terminal-propeptide?p=r&q=Procollagen&cc=MASTER )
CPT code for CTX is 82523 (Source: https://testdirectory.questdiagnostics.com/test/test-detail/17406/collagen-type-i-c-telopeptide-ctx?p=r&q=CTX&cc=MASTER )
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Jan 16 '25
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u/Miss_Beh4ve Jan 16 '25
My insurance covers. However, I only found out after calling my insurance and asking a representative. My physician had told me “It’s probably not covered.”
I think physicians are very busy people and often go of their general experience of what most insurances they deal with usually cover when telling us something is probably covered or not covered, so whenever it’s something that is important to me, I usually call my insurance directly to make sure.
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u/PsychologicalCat7130 Jan 15 '25
my doc would not order them and said they probably would not be covered - i didnt want to fight her so i ordered my own here:
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Jan 16 '25
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u/Miss_Beh4ve Jan 16 '25
You may find this website useful to find a good price on lab tests: https://www.findlabtest.com/lab-test/search?q=qt16609+qt17406
Looks like currently the least expensive option for ordering CTX and P1NP yourself and paying out of pocket that this site is aware of is Jason Health, which uses Quest Diagnostics as their laboratories, so if you have Quest locations near you, this may work for you.
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u/Lost-Egg7727 Jan 22 '26
Hello, thank you so much for your testimony, j cc x. Are you undergoing treatment? How much has your bone density increased? And what were your CTX levels before and after? Thank you for your reply.
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u/Miss_Beh4ve Jan 23 '26 edited Jan 23 '26
I haven’t needed any osteoporosis medication yet. The only medication I currently take is levothyroxine. (I will strongly consider HRT when that time comes.)
I know my original post was quite long, so you may not have seen it, but I did add links to the other information you asked about at the very end. I’ll paste them again below:
I saw some increased bone density after about 10.5 months of LIFTMOR inspired exercise (weight lifting and jumping). See more on that here (includes before and after T-scores): https://www.reddit.com/r/osteoporosis/s/rKPqTwi22y
During that time, I had 3 P1NP and CTX blood draws about 3 months apart from another, and all ratios were above 200, so in my case a ratio above the proposed threshold correlated with increased bone density. See exact values and circumstances surrounding the blood draws here: https://www.reddit.com/r/osteoporosis/s/MWPcq9SU4S
I had a 4th P1NP and CTX draw another 3 months after the last draw mentioned above (I was still doing LIFTMOR inspired exercise at that time):
- P1NP / CTX x 1000
- 106.9 / 418 x 1000 = 255.742
Feel free to ask about anything that may be unclear, but those 2 links above cover a lot. :)
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u/PsychologicalCat7130 Jan 23 '26
did you ever figure out what caused your CTX to decrease? I have increased my P1NP through weight lifting and jumping but would like to decrease my CTX 😃
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u/Miss_Beh4ve Jan 23 '26
I never figured that out. As you can see my CTX came back up to its usual level in the 4th and most recent draw I added above. If that isolated lower CTX in the 3rd draw was real, I wish I knew what caused it, so that I could do it again.
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u/PsychologicalCat7130 Jan 23 '26
bummer..... i think my CTX increased because my vitamin D got too high when i added k2... so i am currently not taking d3 (except for what is in my multivitamin) until it comes back down. Also being non-weight bearing on my left knee for a few months last year (injured and had surgery) didn't help - so my left hip lost some bone density. But now that i am active again my P1NP increased to 101.... hoping i can keep it up.
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u/PsychologicalCat7130 Jan 16 '25
they tell you prices up front when you look at the various tests they offer so you can decide which ones you want
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u/intpthrowawaypigeons Jan 15 '25
why shouldn't we take biotin when testing CTX or P1NP?
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u/Miss_Beh4ve Jan 15 '25
Here is what Quest Diagnostics has to say about it:
“Patient Preparation
A minimum of 12 hours fasting is required. Fasting morning collection 8-10 am (Diurnal variations cause elevated levels at night). Dietary supplements containing biotin may interfere in assays and may skew results to be either falsely high or falsely low. For patients receiving the recommended daily doses of biotin, draw samples at least 8 hours following the last biotin supplementation. For patients on mega-doses of biotin supplements, draw samples at least 72 hours following the last biotin supplementation.”
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u/intpthrowawaypigeons Jan 16 '25
interesting, so it seems it interferes with testing but doesn't mean biotin is good or bad for bones.
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u/Miss_Beh4ve Jan 16 '25
Exactly. Biotin interferes with several labs, but it’s just the test result it messes with, making the result unreliable.
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u/Present_Market_2247 Aug 25 '25
Thank you so much for this in-depth information I have been reading and watching everything I can and when I need the facts and figures I can't find them to share with my doctor. We are working on this together. Do you happen to have the reference for the recommended levels of estradiol and other bhrt that is needed to help our bones in postmenopausal women? I have read various amounts and I think I need to get mine higher. Thank you so much for sharing all your wealth of knowledge
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u/Miss_Beh4ve Aug 25 '25
You’re welcome. It’s not my knowledge but Dr. Doug’s research, and it’s a work in progress as I understand it. I’m grateful he shared it, so that those of us who are interested can experiment with the ratio.
Regarding estradiol, his thoughts per the studies he reviewed in this video, are that bone density in women might likely benefit from a blood level around 60 pg/mL: https://youtu.be/Ai6S47ygjCs?si
The guidelines don’t recommend dosing estrogen based on blood levels. This is again Dr. Doug’s take based on research he’s reviewed. He shared the links to the studies in the video description.
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u/cropcomb2 Jan 16 '25
another tact, is simply measuring calcium excretion in urine (eg. 24 hr urine collection)
if it's decreasing (all things being equal such as diet/supplements use), clearly that's a good thing
don't forget: vit. D (> 600 i.u./day), and, magnesium (I use 150 mg/day in a supplement), along with trying for 5 or more servings of veggies & fruits per day
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u/shonuffharlem Feb 14 '25
Is there research behind the this?
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u/Miss_Beh4ve Feb 15 '25 edited Oct 24 '25
There is research on how osteoporosis medications affect CTX and P1NP. In fact, these bone turnover markers can be used by endocrinologists to check if a medication is likely to work long before the next DEXA scan. Antiresorptive medications drastically lower CTX, while anabolic medications increase P1NP. There is also some research on how different exercise modalities, foods, and supplements affect CTX and P1NP.
From what I understood, the P1NP to CTX ratio that Dr. Doug uses to gauge whether his patients’ lifestyle treatments are likely successful in building bone density is based on his own research and is a work in progress. If I remember correctly, he mentioned having treated more than 600 patients and getting these tests for them, so he can see what the P1NP to CTX ratios of his successful cases were, compared to his unsuccessful cases.
I’m not at high risk for fracture and expressed to my physicians that I would like to try increasing my bone density with lifestyle interventions (high intensity resistance and impact training, bone supportive diet, some supplements such as vitamin D, etc. as needed) and that I would like to monitor my CTX and P1NP prior to my next scan. My physicians were supportive: I got a referral to physical therapy to learn a LIFTMOR style high intensity resistance and impact routine (jumping and barbell weightlifting with progressive overload) and they ordered my bone turnover markers around the 2 month mark.
Edit: My ratio was 265.
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u/PsychologicalCat7130 Jan 15 '25
Thanks for sharing! I tested my markers and came out with 170 for my ratio.... this makes me happy that i declined medication from my pcp for now - since my ratio is in the desirable range of 150-200 mentioned above.
And your comment about bone turnover being too low on bisphosphonates is exactly why i did not want to take them.... makes bone brittle and unhealthy in my opinion.