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Serum C-Terminal Telopeptide of Type I Collagen (CTX)

Published: July 27, 2026Updated: August 25, 2026

The CTX biomarker measures the degradation products of type I collagen, which is the main protein in bone, providing insight into bone resorption rates.

Quick summary

CTX is a marker for bone resorption, aiding in osteoporosis diagnosis and treatment monitoring.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
pg/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche CTX, Abbott CTX, Immunodiagnostic Systems CTX
interpretation: {"text":"May indicate increased bone resorption, suggesting osteoporosis or other metabolic bone diseases.","label":"Elevated levels"}; {"text":"May suggest decreased bone turnover or the effectiveness of antiresorptive treatments.","label":"Lower levels"}

The C-Terminal Telopeptide of Type I Collagen (CTX) is a biomarker that reflects the rate of bone resorption, which is the process by which bone is broken down by osteoclasts. This biomarker is particularly useful in assessing bone turnover in metabolic bone diseases such as osteoporosis.

Elevated levels of CTX in the blood indicate increased bone resorption, which can be associated with conditions like osteoporosis, hyperparathyroidism, and Paget's disease. Conversely, lower levels may suggest decreased bone turnover or the effectiveness of antiresorptive therapies.

CTX testing is often used in conjunction with other bone markers and clinical assessments to monitor the efficacy of osteoporosis treatments and to adjust therapeutic strategies as needed.

Frequently asked questions

What is the normal range for CTX?
The reference range for CTX is typically between 40–150 pg/mL, but this can vary depending on the laboratory and assay used.
How often should CTX be monitored?
The frequency of CTX monitoring depends on the patient's condition and treatment plan, but it is often assessed every 3-6 months during active treatment.
  1. 1
    National Osteoporosis Foundation: Bone Turnover MarkersSource
  2. 2
    Clinical Use of Bone Turnover Markers: An UpdateSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

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Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy