MSRA-0501

MSRA-0501

A 50-year-old woman with a long history of steroid-treated sarcoidosis presents with extreme thirst and nocturia up to five times a night. Her serum calcium concentration is 2.3 mmol/l (reference range 2.2–2.7 mmol/l), random plasma glucose 4.6 mmol/l (reference range <11.1 mmol/l) and potassium 3.5 mmol/l (reference range 3.6–5.2 mmol/l). After an overnight fast, her serum sodium is 149 mmol/l (reference range 135–145 mmol/l).
What is the cause of her symptoms?