MSRA-0497

A 35-year-old woman is brought to the Emergency Department after being found near-unconscious by her husband. He claims she has been increasingly depressed and tired over the last few weeks. Past medical history includes coeliac disease, for which she follows a strict gluten-free diet, and vitiligo. She is on no medical treatment. On examination, she is responsive to pain. Her pulse is 130 bpm and blood pressure is 90/60 mmHg. She is afebrile. Pigmented palmar creases are also noted. Basic blood investigations reveal:
Investigation Result Normal value
Hb 121 g/l 135–180 g/l
WCC 6.1 × 109/l 4–11 × 109/l
Platelets 233 × 109/l 150–400 × 109/l
Na+ 129 mmol/l 135–145 mmol/l
K+ 6.0 mmol/l 3.5–5.0 mmol/l
Creatinine 93 μmol/l 50–120 µmol/l
Glucose 2.7 mmol/l <11.1 mmol/l (random)
What is the most likely diagnosis?