When circulating \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\mathrm{Ca}}_o^{2 + }$$\end{document}Cao2+ levels drop (hypocalcemia), the decrease in parathyroid CaSR activity permits increased PTH secretion which then acts to release Ca2+ and Pi from bone2. Here, CASR is linked to Hypocalcemia.