<prompt> A 33 year old lady presents with polydipsia and polyuria. Her symptoms staed soon after a road traffic accident 6 months ago. The blood pressure is 12080mm Hg with no postural drop. The daily Na 130mEqL, K 3.5 mEqL, urea 15 mgdL, sugar 65 mgdL. The plasma osmolality is 268 mosmolL and urine osmolality 45 mosmolL. The most likely diagnosis is:Central diabetes insipidusNephrogenic diabetes insipidusResolving acute tubular necrosisPsychogenic polydipsia  <response>: Answer is D Psychogenic Polydipsia: Association of decreased urinary osmolality with decreased plasma osmolality along with reduced serum sodium suggests the diagnosis of Primary Polydipsia. 