The parathyroid hormone family consists of parathyroid hormone and parathyroid hormone-like hormone that employ the same parathyroid hormone receptor type 1, a G-protein coupled receptor (GPCR) of family B of GPCRs. Despite signaling through the same receptor, the two hormones elicit distinct functions. Receptor type 2 has been considered an orphan receptor, but a specific ligand has been identified, a 39 residues peptide with weaker amino acid sequence similarity to the two hormones.