PTH and Hypocalcemia: It is also worth noting that our recent studies on a homozygous Arg25→Cys mutation in PTH that is associated with severe hypocalcemia revealed only subtle changes in the functional properties of a Cys25‐PTH(1‐34) analog in cell‐based binding and cAMP signaling assays.(44, 45) Thus, as for the R186H‐PTH1R mutant, the in vitro analyses were limited in their capacity to capture the phenotypic properties associated with this Cys25Arg mutation in PTH.