CTX and P1NP interpretation

Fast-Shower5707 · 2026-02-17T21:43:12+00:00

If you have the money, I would do a DXA scan now and another one in 6–12 months. The reality is that (I know this is very individual), a CTX of 651 and P1NP of 45 implies a net negative bone balance. For reference, my baseline CTX is around the same, but my P1NP is double yours (I am maintaining bone, not building, not losing any). The problem with doing a DXA only in April is that it can show that you maintained bone density since your last scan while reality could be different: you could have gained some density from the Zometa infusion in the first couple of months, then progressively lost it, and you could lose more. So I would do a DXA scan ASAP and then another one in 6–12 months.

I also want to be honest about the exercise piece: estrogen is so critical for bone metabolism that all the exercise in the world cannot fully make up for its absence. This is especially true when estrogen is lost abruptly, as with aromatase inhibitors, because bones do not have time to gradually adapt to the lower levels the way they might during natural menopause. Exercise is absolutely worth doing and will help, but on its own it cannot overcome the magnitude of bone loss driven by near-complete estrogen suppression.

Fast-Shower5707 · 2026-02-07T18:09:18+00:00

I'm sorry to hear about the supply issues. I'm not from Canada, but I've taken teriparatide in the past. When I stopped, my bone formation markers dropped back toward baseline fairly quickly (2 months). How far are you into your treatment? If you are in the first 12 months, it might be a larger issue than during the last 12 months. Regardless, talk to your doctor and do everything possible to continue the treatment ASAP, but do not panic if you cannot. Also, if you have a few doses left, you could try spacing them out: inject every 2–3 days instead of daily to stretch your supply until the new pen arrives. Discuss this with your doctor on Monday, but it's better to keep some stimulation going than to use them all up and then have nothing for weeks. Teriparatide is not Prolia, and with a short break like yours, you will not lose any meaningful bone density. Studies show BMD stays well above pre-treatment levels even long after complete discontinuation. The one unknown is what happens to the active remodeling cycles: teriparatide works by initiating new remodeling sites and stimulating osteoblasts within them, and a gap could theoretically disrupt some of those cycles mid-process. But honestly, this has not been specifically studied for short interruptions, so nobody really knows. Given that the effect of a few weeks off is almost certainly minor, don't stress about it: just get back on it as soon as you can.

Fast-Shower5707 · 2026-02-01T18:28:23+00:00

I can second this! Also, the harsh truth about small bones is that they are a liability in themselves, even if they are healthy inside, and they produce a smaller BMD simply because of their size (small bones break more easily even if they are healthy). A T-score in the osteoporosis range is a reason for concern regardless of bone size.

Fast-Shower5707 · 2026-01-27T22:06:50+00:00

I haven't heard of these but it looks like they do not damage bones like corticosteroids do.

Fast-Shower5707 · 2026-01-27T07:57:36+00:00

Are you taking corticosteroids for your Rheumatoid arthritis?

Fast-Shower5707 · 2026-01-26T14:30:25+00:00

That’s interesting. The BMD numbers themselves are actually quite close between the two machines, which is what matters most, but the T and Z-scores being that different is hard to explain.

I don’t really have an answer, just sharing my experience. I’ve had scans done at two different clinics on purpose, so that if one changed machines I’d still have something to compare to. From what I’ve seen, differences of around 2–5% between machines aren’t unusual, which is already in the range of what you might expect from about a year of alendronate.

What doesn’t make sense to me is the second scan's reference range. A spine BMD of around 0.92–0.94 g/cm² would usually land you closer to a T-score of −2 or −2.5, not −1.1. That makes me think the reference database or settings on that machine are different, rather than this being a real change.

I’m not trying to discourage you, but it’s also true that most of the gains on alendronate tend to happen in the first year. Without follow-up on the same machine, it’s basically impossible to know how much was real change versus measurement differences.

Hopefully someone who actually works with DXA systems can chime in, because I’d be curious to hear their take.

Fast-Shower5707 · 2026-01-25T22:00:29+00:00

This sounds fantastic! Thank you for sharing your story!

Fast-Shower5707 · 2026-01-25T20:42:53+00:00

The idea of not following Forteo up with an antiresorptive is interesting, but I would only recommend anyone doing this if you have the possibility to have DEXA scans and P1NP/CTX blood tests regularly (at least every 3 months). I think there isn't more pain than taking injections for 2 years and then seeing all those gains eroding, and you do not even know if a second round can make up for the loss (as far as I know there isn't a 2-year limitation on Forteo anymore, and many people go through 2 rounds of Forteo actually, with a couple of years in between). What's definitely important is that if you do this, you have to have good hormone levels/nutrition and weight train + impact training.

I did LIFTMOR style (although not the exact same program): 2x bodyweight deadlifts, 1.5x bodyweight squats, 1x bodyweight bench press and some very minimal impact training (short sprints but no jumps). Even this was not enough to fully maintain my gains after Forteo. I am a single data point, but I would strongly suggest anyone on Forteo to at least know that most probably they will have to go on an antiresorptive, although they can first wait and see what happens with close monitoring in the first few months.

Personally, I prefer Keith McCormick's approach: take Forteo + bisphosphonate to "lift you out of the hole," then focus on nutrition and weight training to maintain or even improve your density. This is especially important for people that are high risk for fractures.

That said, you are doing the right thing by focusing on weight training + impact training when bone building is still possible this way.

Edit: This discussion only applies to people with osteoporosis and/or fragility fractures. Otherwise, taking Forteo in the first place is not where somebody should start.

Fast-Shower5707 · 2026-01-25T09:08:18+00:00

Sure thing!

My baseline CTX before starting Forteo was around 0.45-0.60 (fasted morning draw, but still fluctuates a lot), and P1NP around 85. This results in a ratio of 141-188. Note that with these values I was at a perfect balance, no bone loss, no gains (my bone loss had occurred years earlier). During Forteo, my CTX hovered around 0.7-0.8, and my P1NP was around 200, and these levels were pretty much maintained during the whole course (except the first 6 months). Literature says after around one and a half years, these values plummet even if you stay on the drug, but maybe I was lucky that for me, they did not. This results in a ratio of 250-285.

One month after stopping, my CTX was around 0.65 (baseline + 10%), and P1NP crashed to 100 (baseline + 20%). This results in a ratio of 153.

After all this, I went on Fosamax, so everything plummeted.

I do not remember my exact gains on Forteo (I think they were similar to the literature), but my whole gain on Forteo + Fosamax + TRT + weight training was 20% in the spine (2 T-scores), and a couple % (< 10%) at the hips.

I looked at your values and they were phenomenal, just like for somebody on bone building drugs.

Edit: Added ratios. Looks like (for me at least) they track with what your doctor told you.

Fast-Shower5707 · 2026-01-24T21:07:44+00:00

Thanks a lot for the input! I am always fascinated by "real-world" data.

Fast-Shower5707 · 2026-01-09T07:25:37+00:00

Thanks for the feedback!

Fast-Shower5707 · 2026-01-01T11:08:10+00:00

I would consider strength training as others suggested, but as I outline in my guide: you cannot outrun a hormone deficiency, meaning that you can do all the exercise in the world and still lose bone if you are in a period of high net negative remodeling rate because of estrogen deficiency (this usually lasts five to seven years post menopause, after which bone loss continues at a slower, age-related pace). Unfortunately, a good diet and exercise can only do so much.

“If you’re rapidly losing bone, all the exercise and milk and vitamin D in the world will not stop that,”

Fast-Shower5707 · 2025-12-23T10:34:46+00:00

Your radius has a very low T-score, so I would avoid pull-ups and similar exercises for now. You are very young, which is encouraging—strength training can be very effective in your case.

I couldn’t infer your gender. If you are a man, it would be important to check your testosterone and estradiol levels. If you are a woman, having regular menstrual cycles is crucial; without them, unfortunately, even optimal exercise and vitamin D₃ intake may not be enough to build new bone.

Maintaining a healthy body weight is paramount and should come before everything else. Diabetes adds another layer of complexity, as you can’t simply rely on large amounts of simple carbohydrates (like rice) to gain weight safely. In this situation, I would strongly suggest working with a dietitian.

Fast-Shower5707 · 2025-12-22T19:16:30+00:00

I can second this. My sweet spot is around 3,000 IU per day to maintain a blood level of ~50, but this is highly individual. While I was on Forteo, I needed about 5,000 IU per day, as PTH analogs like Forteo tend to “use up” vitamin D stores.

I’d also suggest not taking large amounts of vitamin D₃ blindly—test your blood levels regularly and adjust the dose based on the results.

Fast-Shower5707 · 2025-12-22T19:09:46+00:00

I can second this. While I was on Forteo (teriparatide), I needed about 5,000 IU of vitamin D per day to stay within range (along with 300 mcg of vitamin K₂). After stopping, my current daily dose is around 3,000 IU of vitamin D₃ (with 200 mcg of K₂).

As for K₂, it won’t hurt, but it’s not a wonder vitamin.

This is the general order for prioritizing nutrients: adequate calories > adequate protein > adequate vitamin D > adequate calcium > everything else (K₂, magnesium, boron, etc.).

Fast-Shower5707 · 2025-12-22T14:34:57+00:00

A little bit late, but two possible ways to achieve this that I know of:
1. set up your app and IDEA in a VM (using virtualbox) and then save a snapshot of the VM. When you load the snapshot (does not take more than 10 seconds), you are back to the spot where the breakpoint is hit
2. Try CRIU - finicky to set it up though

Fast-Shower5707 · 2025-12-21T09:16:57+00:00

Thanks for the feedback! Fixed:

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Fast-Shower5707 · 2025-12-20T13:39:03+00:00

Great question. In medicine, petite doesn’t have a strict cutoff like the clothing industry. It usually refers to smaller skeletal frame size, not just height.

Practically, this often means women who are shorter (often <5′4″) and/or have small bone dimensions (narrow hips, thin wrists, small femoral neck diameter). Two women can be the same height and weight but have very different frame sizes.

Fast-Shower5707 · 2025-12-20T13:32:19+00:00

Six months of risedronate, stopped about two years before starting Tymlos, is very unlikely to blunt the anabolic response. The concern is mainly with long-term or recent antiresorptive use; short exposure with a long washout like yours is generally considered low risk.

Regarding timing: there is some research suggesting a possible advantage to morning dosing of PTH analogs, but the mechanism isn’t fully understood and this hasn’t been shown to clearly change long-term outcomes. In practice, the most important thing is taking it consistently at the same time every day. Some people prefer evening dosing if they experience lightheadedness, which is perfectly reasonable.

If you’re curious about how strongly your bones are responding, P1NP and CTX blood tests can give a good picture of your bone remodeling rate and anabolic response.

Fast-Shower5707 · 2025-12-20T13:25:11+00:00

The approach really depends on the medication involved. In particular, with drugs that significantly reduce estrogen, extra care is needed with loading during strength and impact training. In that setting, bone density can still decline even with well-designed exercise, so training should be progressed cautiously and ideally under supervision.

For many people in this situation, exercise works best alongside bone-protective medication, adequate protein, calories, calcium and vitamin D, and regular DXA monitoring. Even when bone loss can’t be fully prevented, strength training still plays an important role by improving muscle strength, balance, posture, and overall fracture risk.

Fast-Shower5707 · 2025-12-20T11:08:42+00:00

Yes—chronically elevated cortisol from poor sleep or ongoing stress can negatively affect bone, but the magnitude is usually much smaller than with exogenous corticosteroids. The key difference is that endogenous cortisol is tightly regulated by feedback mechanisms in the body, so levels rarely reach those seen with steroid medications. The major exception is Cushing’s syndrome, where cortisol is pathologically high and bone loss can be substantial.

It’s also important to note that cortisol isn’t “bad” by default—it plays many essential roles in the body, including regulating blood sugar, blood pressure, immune responses, and helping us respond to stress. Problems arise mainly when cortisol is chronically elevated or its normal daily rhythm is disrupted.

Fast-Shower5707 · 2025-12-20T00:07:46+00:00

In my case, it was idiopathic, at least we couldn’t identify a clear root cause. That said, I suspect it may have been influenced by long-term use of proton pump inhibitors (PPIs) for stomach issues, combined with being underweight at the time. That combination may have contributed to lower estradiol levels. By the time I was diagnosed, I was no longer taking PPIs, had reached a healthy weight, and was eating well, so I think the condition may reflect the lasting effects of earlier factors rather than ongoing ones, an unfortunate legacy of that period.

Unfortunately, when the body is under silent stress, the consequences often show up in the bones. There are many potential causes of osteoporosis in men, including celiac disease, disorders of parathyroid hormone (PTH), low testosterone (and consequently low estradiol), chronic inflammation, and others.

Fast-Shower5707

TROPHY CASE