An 18-year-old woman presented with a 2-month history of polyuria and polydipsia. She had been previously fit and well w

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An 18-year-old woman presented with a 2-month history of polyuria and polydipsia. She had been previously fit and well with regular periods. She was not taking any contraception.Investigations:serum potassium5.2 mmol/L (3.54.9)serum corrected calcium2.30 mmol/L (2.202.60)serum cortisol (09.00 h)350 nmol/L (200700)She went on to have a water deprivation test, the results of which are detailed below. time (h)serum osmolality (mosmol/kg)urine osmolality (mosmol/kg) normal: 278300normal: 100100008.302895211.302928214.3030115315.30-172She was then given intramuscular DDAVP 2 micrograms at 16.00 h. time (h)serum osmolality (mosmol/kg)urine osmolality (mosmol/kg) normal: 278300normal: 100100016.30300-17.30-53018.30-532Results from an MR scan of pituitary are shown (see image).What is the most likely diagnosis?

An 18 Year Old 1 (195.85 KiB) Viewed 87 times

A. autoimmune (lymphocytic) hypophysitis
B. craniopharyngioma
C. non-functioning pituitary adenoma
D. psychogenic polydipsia E. Rathke’s cleft cyst