Role of Magnesium in Parathyroid Physiology

Magnesium (Mg2+) is a divalent cation that is essential for numerous physiologic processes. Ninety-nine percent of it is contained in the intracellular compartment, while 1 % is found in the extracellular fluid. Maintenance of total serum Mg2+ within a narrow range (0.70-1.1 mmol/L) is dependent on the coordinated actions of the kidneys, gut and bone. Ninety percent of intestinal absorption and renal reabsorption of Mg2+ occurs passively via the paracellular route, while 10 % occurs transcellularly, which is an energy-dependent process. Transient receptor potential melastatin subtype 6 (TRPM6) is the main channel responsible for active transport of Mg2+ in the gut and kidneys. Mg2+ levels and parathyroid hormone (PTH) depend on each other in an intricate manner. The calcium-sensing receptor (CaSR) is physiologically activated not only by calcium (Ca2+) but by Mg2+ as well. Thus, disturbances in Mg2+ balance may lead to secondary hypocalcemia via its inhibitory effects on PTH secretion and action. Further research is required in order to ameliorate our understanding of Mg2+ homeostasis, as well as the role of Mg2+ in parathyroid physiology.