PTH and familial primary hypomagnesemia: Hypomagnesemia is associated with impaired release of PTH from the parathyroid cell, likely through a disturbance in the stimulus-secretion coupling mechanism.(105) Because both Mg and Ca activate the CaSR and reduce PTH synthesis and secretion,(106) albeit with different potencies, elevated levels of extracellular Mg can lead to functional hypoparathyroidism.