Type I collagen C-terminal telopeptide (CTX-I)

Type I collagen C-terminal telopeptide (CTX-I) is a peptide fragment released into the systemic circulation during the degradation of Type I collagen, the primary structural component of the bone matrix [2, 7]. It is generated specifically by the action of osteoclast-derived enzymes, most notably Cathepsin K, during the process of bone resorption [9]. As such, CTX-I serves as a highly sensitive and specific biochemical marker for bone turnover and is widely utilized in clinical practice to assess the rate of bone loss [2, 5]. Elevated levels of CTX-I are associated with conditions characterized by increased bone resorption, including osteoporosis, Paget's disease, and bone metastases from various cancers [5, 6]. While not a direct therapeutic target itself, CTX-I is a critical tool for monitoring the efficacy of anti-resorptive therapies, such as bisphosphonates and denosumab, which aim to reduce its production by inhibiting osteoclast activity [2, 5]. Its measurement allows for early assessment of treatment response, often preceding changes in bone mineral density [6, 7].

Other names

CTXCTX-Ibeta-CTXCrossLapsCarboxy-terminal telopeptide of type I collagenICTP

Drugs associated with this molecule do not target it directly; instead, they inhibit the biological processes (e.g., osteoclast-mediated bone resorption) or enzymes (e.g., Cathepsin K) that lead to its release from the bone matrix, thereby reducing its concentration in serum and urine [2, 9].