Which statement accurately describes the site of action of thiazide diuretics?

Which statement accurately describes the site of action of thiazide diuretics?

• A. They act on the proximal tubule to inhibit carbonic anhydrase
• B. They increase potassium reabsorption
• C. They produce diuresis by increasing calcium excretion in the collecting duct
• D. They increase excretion of Na+ and Cl- in the distal convoluted tubule

Answer: (D)

Thiazide diuretics act in the distal convoluted tubule by inhibiting the Na+-Cl- cotransporter, which reduces reabsorption of sodium and chloride and increases their excretion in the urine. This location and mechanism explain the modest diuretic effect and how more sodium delivery to the collecting duct can promote potassium secretion, potentially causing hypokalemia. They also tend to increase calcium reabsorption in the distal tubule, reducing calcium excretion. By contrast, carbonic anhydrase inhibitors act in the proximal tubule, and thiazides do not work by increasing calcium excretion.

Thiazide diuretics act in the distal convoluted tubule by inhibiting the Na+-Cl- cotransporter, which reduces reabsorption of sodium and chloride and increases their excretion in the urine. This location and mechanism explain the modest diuretic effect and how more sodium delivery to the collecting duct can promote potassium secretion, potentially causing hypokalemia. They also tend to increase calcium reabsorption in the distal tubule, reducing calcium excretion. By contrast, carbonic anhydrase inhibitors act in the proximal tubule, and thiazides do not work by increasing calcium excretion.