Which of the following biological signs points you towards iatrogenic adrenal insufficiency in a 38-year-old patient with a history of Crohn's disease treated for 5 years with 10 mg/day of prednisone?
Sodium at 128 mmol/l
Potassium at 5.8 mmol/l
Fasting blood sugar at 3 mmol/l
Plasma acth at 8 hours at 585 pg/ml (n: 10 – 20)
Urinary free cortisol at 25 µg/24 hours (n: < 90)