Gitelman syndrome (GS) is an autosomal recessive kidney tubule disorder characterized by low blood levels of potassium and magnesium, decreased excretion of calcium in the urine, and elevated blood pH. The disorder is caused by disease-causing variants in both alleles of the SLC12A3 gene. The SLC12A3 gene encodes the thiazide-sensitive sodium-chloride cotransporter (also known as NCC, NCCT, or TSC), which can be found in the distal convoluted tubule of the kidney. The distal convoluted tubule of the kidney plays an important homeostatic role in sodium and chloride absorption as well as of the reabsorption of magnesium and calcium. Genetic mutations of NCC, lead to loss of function and subsequently, reduced transport of sodium and chloride via NCC. Secondary derangement of calcium, magnesium, and potassium concentrations are caused by secondary effects in the distal tubule and collecting duct. The effect is an electrolyte imbalance similar to that seen with thiazide diuretic therapy (which causes pharmacological inhibition of NCC activity). Gitelman syndrome was formerly considered a subset of Bartter syndrome until the distinct genetic and molecular bases of these disorders were identified. Bartter syndrome is also an autosomal recessive cause of hypokalemic metabolic alkalosis, but it derives from a mutations of a number of genes that reduce NKCC2 activity. NKCC2 is found in the thick ascending limb of the loop of Henle. From Wikipedia
