Hyponatremia due to increased sodium loss EXCEPT

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Hyponatremia due to increased sodium loss happens when the kidneys waste sodium, so the serum sodium falls because Na+ is lost in urine rather than because too much water is retained. Diuretic use promotes natriuresis by blocking Na+ reabsorption in the renal tubules, directly causing sodium loss and hyponatremia. Hypoadrenalism reduces aldosterone, leading to decreased Na+ reabsorption and increased urinary Na+ loss, also producing hyponatremia. Potassium deficiency often accompanies diuretic use or mineralocorticoid effects that promote sodium loss, so it fits the pattern of Na+ loss–related hyponatremia. Renal failure, by contrast, typically causes hyponatremia mainly through dilutional effects from impaired free-water excretion rather than direct loss of sodium in the urine, making it the exception.