What causes hyponatremia?

What causes hyponatremia?

• A. Dehydration due to sweating
• B. Vitamin deficiency
• C. Excessive intake of hypertonic saline
• D. Overconsumption of hypotonic fluids combined with reduced renal water clearance

Answer: (D)

Hyponatremia happens when there’s too much water relative to sodium in the body, so the serum sodium gets diluted. The kidneys normally handle this by excreting free water. When someone drinks large amounts of hypotonic fluids (water), and the kidneys’ ability to clear that water is reduced, the excess water can’t be dumped quickly enough. That excess free water dilutes the sodium in the blood, producing hyponatremia. Context helps: the amount of free water the kidneys can excrete depends on the solute load you’re delivering to the kidneys and on hormonal control of water balance. If solute intake is low or water retention is inappropriately high (for example, due to antidiuretic hormone activity) or renal function is impaired, the kidneys can’t remove water efficiently. Under those conditions, drinking a lot of plain water or other hypotonic fluids pushes the balance toward dilution, lowering serum sodium. Dehydration from sweating would not cause hyponatremia; it tends to raise sodium concentration because water loss is often accompanied by salt loss. Vitamin deficiency isn’t a direct cause of hyponatremia, and excessive intake of hypertonic saline would raise, not lower, serum sodium.

Hyponatremia happens when there’s too much water relative to sodium in the body, so the serum sodium gets diluted. The kidneys normally handle this by excreting free water. When someone drinks large amounts of hypotonic fluids (water), and the kidneys’ ability to clear that water is reduced, the excess water can’t be dumped quickly enough. That excess free water dilutes the sodium in the blood, producing hyponatremia.

Context helps: the amount of free water the kidneys can excrete depends on the solute load you’re delivering to the kidneys and on hormonal control of water balance. If solute intake is low or water retention is inappropriately high (for example, due to antidiuretic hormone activity) or renal function is impaired, the kidneys can’t remove water efficiently. Under those conditions, drinking a lot of plain water or other hypotonic fluids pushes the balance toward dilution, lowering serum sodium.

Dehydration from sweating would not cause hyponatremia; it tends to raise sodium concentration because water loss is often accompanied by salt loss. Vitamin deficiency isn’t a direct cause of hyponatremia, and excessive intake of hypertonic saline would raise, not lower, serum sodium.