A recombinant therapeutic agent that is identical or similar to an 84-amino-acid polypeptide produced by the parathryoid gland which functions to maintain a constant concentration of calcium ions (Ca2+) in the extracellular fluid. In target tissues, parathyroid hormone (PTH) binds to and activates the parathryorid hormone receptor (PTHR), a cell surface G protein-coupled receptor; there are two types of receptors, parathyroid hormone receptor 1 (PTH1R) found in bone and the kidney and parathyroid hormone receptor 2 (PTH2R) found primarily in the central nervous system (CNS), pancreas, testis, and placenta. Activation of PTHRs results in the activation of adenylyl cyclase and phospholipase C in target tissue cells, which, depending upon the specific target tissue, results in the enhancement of intestinal Ca2+ absorption, mobilization of bone Ca2+, and renal Ca2+ reabsorption.