CTX

**Semantic type:** Amino Acid, Peptide, or Protein

**Definition:** This polypeptide is comprised of the carboxy-terminal portions of fibrillar collagen, which are joined through trivalent crosslinks and released during the degradation of mature type I collagen by cathepsin K. Serum concentrations of these peptides can be correlated with the rate of bone metabolism.

**Synonyms:** - C-Telopeptide - C-Terminal Telopeptide Type 1 Collagen - C-Terminal Telopeptide Type I Collagen - CTX-I - CTXI - Collagen Type 1 Cross-linked C-Telopeptide - Cross-Linked C-Terminal Telopeptide of Type I Collagen