FCA1-0335

FCA1-0335

A 72-year-old woman with a medical history of ischaemic heart disease, hypertension, and hypothyroidism was brought to ER with a change in her mental state over the past few hours. Medications used by her were hydrochlorothiazide, aspirin, ramipril, and levothyroxine. On physical examination, decreased skin turgor, orthostatic hypotension, and disorientation of time and place were found. There were no significant neurological signs. Initial biochemical tests are as follows: Na: 111 mmol/L (135-145), K: 4.1 mmol/L (3.5-5.1), Cl: 105 mmol/L (99-101), Bic: 29 mmol/L (22-29), Urea: 16.4 mmol/L (1.7-8.3), Creatinine: 320µmol/L (44-80), Glucose: 13.5mmol/L (3.5-5.5), Plasma osmolality: 278mOsm/kg, Urinary osmolality: 450mOsm/kg, TSH: 6.2 miu/L (0.1-6.0), Free T4: 10.1 pmol/L (10-25), Free T3: 1.4nm/L (1.0-2.5), Which of the following is most likely cause for this condition of the patient?