Gitelman syndrome arises from dysfunction of the distal convoluted tubule Na-Cl cotransporter, leading to metabolic alkalosis and hypomagnesemia. Which nephron segment is affected?

Gitelman syndrome arises from dysfunction of the distal convoluted tubule Na-Cl cotransporter, leading to metabolic alkalosis and hypomagnesemia. Which nephron segment is affected?

• A. Proximal tubule
• B. Distal tubule
• C. Loop of Henle
• D. Collecting duct

Answer: (B)

The distal convoluted tubule is the nephron segment affected. Its Na-Cl cotransporter is the key transporter in this segment, and Gitelman syndrome results from dysfunction of that transporter, producing a thiazide-like effect: reduced NaCl reabsorption leads to mild volume depletion, RAAS activation, and a metabolic alkalosis. Magnesium reabsorption mainly occurs in the distal convoluted tubule, so impaired function here also causes hypomagnesemia. The other segments—proximal tubule, loop of Henle, and collecting duct—do not house the Na-Cl cotransporter, so they are not the primary site of this disorder.

The distal convoluted tubule is the nephron segment affected. Its Na-Cl cotransporter is the key transporter in this segment, and Gitelman syndrome results from dysfunction of that transporter, producing a thiazide-like effect: reduced NaCl reabsorption leads to mild volume depletion, RAAS activation, and a metabolic alkalosis. Magnesium reabsorption mainly occurs in the distal convoluted tubule, so impaired function here also causes hypomagnesemia. The other segments—proximal tubule, loop of Henle, and collecting duct—do not house the Na-Cl cotransporter, so they are not the primary site of this disorder.