Understanding Osteoporosis and osteopenia

Have you recently been diagnosed with osteoporosis or osteopenia and found yourself unsure about what it really means and what steps to take next?

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Understanding Bone Health Tests: CTX, P1NP, and More

A simple introduction
Bone is constantly being broken down and rebuilt. In osteoporosis, this balance is disrupted. Blood tests such as CTX and P1NP help us understand this process more clearly. Work led by Pierre Szulc has shown that, when measured properly, these markers can give a reliable and practical way to monitor bone health and how well treatments are working.

What are CTX and P1NP?

  • CTX shows how quickly bone is being broken down

  • P1NP shows how new bone is being made

  • Together, they give a simple picture of how active your bones are

Are they reliable?

  • Yes, when done properly, they are widely used and trusted (Note CTX must be done in the morning and fasting)

  • Most useful for tracking how well treatment is working over time

When are these tests used?

  1. Before starting treatment (to get a baseline)

  2. A few months after starting treatment (to check response)

  3. Sometimes later to make sure things stay stable

What is the best time to do the test?

  • CTX:

    • Early morning

    • Fasting (no food overnight)

  • P1NP:

    • More stable, but usually done at the same time as CTX for consistency

How to interpret results (simple examples)

  • Antiresorptive treatments (slow bone breakdown):

    • Examples: alendronate, risedronate, zoledronic acid, denosumab

    • Expected pattern:

      • CTX decreases (e.g. 0.6 → 0.2)

      • P1NP decreases (e.g. 50 → 25)

    • Why does P1NP also fall? (simple explanation)

      • When bone breakdown is reduced, the signal to make new bone also decreases

      • Less old bone is being removed, so the body slows down building new bone

      • This is normal → P1NP decreases slightly as part of treatment effect

  • Anabolic treatments (build new bone):

    • Examples: teriparatide, abaloparatide, romosozumab, (in some settings) growth hormone-related therapies

    • Expected pattern:

      • P1NP increases (e.g. 40 → 80)

      • CTX may also rise slightly early on

  • The key is the trend over time, not a single number

Simple combined score (easy way to understand balance)

  • A simplified way to look at bone balance is:

    • Score = (P1NP ÷ CTX)

  • Example:

    • P1NP = 60 µg/L, CTX = 0.3 µg/L

    • Score = 60 ÷ 0.3 = 200

  • Suggested interpretation:

    • 150–200 → good bone formation balance

    • Lower → relatively more bone breakdown

    • Higher → relatively more bone formation

  • This is a simple guide only and not part of formal clinical guidelines

How often are they repeated?

  • Usually checked again at 3–6 months after starting treatment

  • Always try to repeat under the same conditions

Other important tests for bone health

  • DEXA scan – measures bone density

  • RMS (if used locally) – additional bone assessment

  • Blood tests:

    • Calcium

    • Vitamin D

    • Thyroid hormones

    • Sex hormones (e.g. oestrogen/testosterone)

In summary

  • CTX and P1NP help monitor bone activity

  • Timing and consistency matter, especially for CTX

  • Results should always be looked at as trends over time, alongside scans and other blood tests

Need help?
If you would like help interpreting your results or advice on when and how to arrange these tests, you can get in touch for further guidance.

Contact me