Gitelman syndrome (GS) is an autosomal recessive disorder caused by genic mutations of SLC12A3 (Solute carrier family 12 member 3), which encodes the Na-Cl cotransporter (NCC), and presents with characteristic metabolic abnormalities, including hypokalemia, metabolic alkalosis, hypomagnesemia, and hypocalciuria. The gene discussed is SLC12A3; the disease is Hypomagnesemia.