Which part of the nephron does hydrochlorothiazide primarily target?

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

Answer: (B)

Hydrochlorothiazide targets the distal convoluted tubule, where it blocks the sodium-chloride cotransporter. By inhibiting Na+ and Cl− reabsorption in this segment, more sodium stays in the filtrate and water follows, producing a milder diuretic effect that helps reduce blood pressure and edema. This distal tubule site explains why thiazides are less potent diuretics than loop diuretics (which act on the loop of Henle) and are not primarily effective in the proximal tubule or collecting duct. The action here also helps increase calcium reabsorption, which can be beneficial in some conditions like kidney stones.