<prompt> A smoker presented with altered sensorium. His blood osmolality was found to be 240 and urine osmolality 340. His Na is 122 meqL. The diagnosis isDiabetes insipidusSIADHRenal tubular acidosisCerebellar degeneration  <response>: B SIADH Psychogenic polydipsia and beer potomania--Marked excess free water intake generally 10 Ld may produce hyponatremia. Euvolemia is maintained through the renal excretion of sodium. Urine sodium is therefore generally elevated 20 mEqL, but unlike SIADH, levels of ADH are suppressed. Urine osmolality is appropriately low 300 mosmkg as the increased free water is excreted. Hyponatremia from bursts of ADH occurs in manic-depressive patients with excess free water intake. Psychogenic polydipsia is observed in patients with psychological problems, and these patients frequently take drugs interfering with water excretion. Similarly, excessive intake of beer, which contains very small amounts of sodium 5 mEqL, can cause severe hyponatremia in cirrhotic patients, who have elevated ADH and often a decreased GFR. 