C-terminal parathyroid hormone receptor (CPTHR) (CPTHR)

The C-terminal parathyroid hormone receptor (CPTHR) is a specialized receptor that specifically binds to the carboxyl-terminal fragments of parathyroid hormone (PTH), such as PTH(53-84) and PTH(39-84) (Divieti et al., 2001). While the well-characterized PTH1 receptor (PTH1R) mediates the classical calcemic actions of PTH via its N-terminal domain, the CPTHR appears to mediate distinct and often opposing biological effects, particularly in bone metabolism (Slatopolsky et al., 2000). It is predominantly expressed in osteoblasts and osteocytes, where it is thought to inhibit bone resorption and promote osteocyte survival (D'Amour, 2012). In clinical contexts, particularly chronic kidney disease (CKD), C-terminal PTH fragments accumulate significantly due to reduced renal clearance, potentially leading to skeletal resistance to PTH by competing for binding or exerting inhibitory effects through the CPTHR (Murray et al., 2005). Although the molecular identity of the CPTHR has been a subject of ongoing research and it has not been cloned as a unique gene, it is functionally classified as a G protein-coupled receptor (Bringhurst, 2002). Understanding this receptor is crucial for managing renal osteodystrophy and developing more precise therapies for metabolic bone diseases.

Other names

C-PTH receptorCPTH-RPTH-C receptorCarboxyl-terminal PTH receptor

Agonism of the CPTHR by C-terminal fragments of PTH, which modulates bone turnover and osteocyte activity, often opposing the actions of the PTH1 receptor (Slatopolsky et al., 2000; D'Amour, 2012).