Which hormone reduces sodium reabsorption and increases urine volume?

• A. ADH
• B. Aldosterone
• C. Angiotensin II
• D. ANP

Answer: (D)

The body uses a natriuretic hormone to reduce sodium reabsorption and increase urine volume. When the atria are stretched by higher blood volume, atrial natriuretic peptide is released. ANP counteracts the renin–angiotensin–aldosterone system by inhibiting renin release and lowering aldosterone levels, and it also directly reduces sodium reabsorption in the distal nephron and collecting ducts. In addition, ANP can raise the glomerular filtration rate, increasing the filtered load of sodium that can be excreted. The combined effect is sodium wasting (natriuresis) with an accompanying rise in urine volume, which helps lower blood volume and pressure. By comparison, hormones like ADH promote water reabsorption, while aldosterone and angiotensin II enhance sodium reabsorption, so they do not produce the same diuretic outcome.