During cold exposure, what hormonal changes contribute to diuresis?

• A. Increased AVP/ADH and decreased natriuretic peptide signaling
• B. Reduced AVP/ADH and increased natriuretic peptide signaling
• C. Increased aldosterone and antidiuretic hormone
• D. Decreased atrial natriuretic peptide and decreased renin

Answer: (B)

Cold exposure triggers diuresis through two complementary hormonal shifts. The body constricts skin vessels to conserve heat, which increases venous return and stretches the atria. That atrial stretch stimulates release of natriuretic peptides, especially atrial natriuretic peptide, which promotes natriuresis and diuresis by increasing glomerular filtration and reducing sodium reabsorption in the collecting ducts, while also opposing the renin-angiotensin-aldosterone system. At the same time, antidiuretic hormone (AVP/ADH) release is reduced, lowering water reabsorption in the collecting ducts and allowing more free water to be excreted. The combination of less AVP-driven water reabsorption and more natriuretic peptide–driven salt and water loss accounts for the diuresis seen in cold conditions.