Gitelman’s syndrome (GS) is a genetic tubulopathy caused by loss-of-function mutations in the SLC12A3 gene, which encodes the Na+-Cl− cotransporter and is characterized by hypokalemic metabolic alkalosis, hypocalciuria, hypomagnesemia, activated Renin-Angiotensin System (RAS) and high Angiotensin II (Ang II) levels. The gene discussed is SLC12A3; the disease is Hypocalciuria.