Which of the following is listed as a hyponatremia cause under 'Other causes'?

• A. Diabetic acidosis
• B. Salt-restricted diet
• C. Hyperglycemia
• D. Hypernatremia

Answer: (A)

Hyponatremia can arise when there is a hyperglycemic state, and diabetic acidosis is a classic example of this mechanism. In high glucose conditions, serum osmolality rises and water shifts from the intracellular space into the extracellular space to balance the osmotic gradient. This influx of water into the extracellular compartment dilutes the sodium concentration, producing what we see as hyponatremia. In diabetic acidosis, this dilutional effect is often evident alongside total body sodium depletion from osmotic diuresis, so the sodium appears low even though the body is actually sodium-depleted.

So, among the options, diabetic acidosis is the hyponatremia cause listed under “Other causes” because it reflects the osmotic dilution from marked hyperglycemia. The other options don’t fit this category: a salt-restricted diet isn’t a direct acute hyponatremia cause in standard classifications, hyperglycemia explains the mechanism rather than naming a separate cause, and hypernatremia would raise sodium rather than lower it.