A 75-year-old woman presented with a 4-week history of lethargy. Her medical history was unremarkable and she took no medication.
On examination, her blood pressure was 140/70 mmHg lying. She was euvolaemic.
Investigations:
serum sodium120 mmol/L (137C144)
serum potassium3.8 mmol/L (3.5C4.9)
serum urea3.0 mmol/L (2.5C7.0)
serum creatinine75 µmol/L (60C110)
short tetracosactide (Synacthen®) test (250 micrograms):
baseline serum cortisol450 nmol/L (200C700)
serum cortisol (30 min after tetracosactide)600 nmol/L (>550)
serum thyroid-stimulating hormone2.5 mU/L (0.4C5.0)
serum free T416.9 pmol/L (10.0C22.0)
urinary sodium70 mmol/L
What is the most appropriate initial management?
A . demeclocycline
B . fluid restriction
C . hydrocortisone
D . intravenous sodium chloride 0.9%
E . tolvaptan
Answer: B