26th April 2024

A 32-year-old woman presents with a six-month history of increasing fatigue, weight loss, and hyperpigmentation of her skin, particularly in her hands, elbows, and knees. She reports experiencing dizziness.

A 32-year-old woman presents with a six-month history of increasing fatigue, weight loss, and hyperpigmentation of her skin, particularly in her hands, elbows, and knees. She reports experiencing dizziness. Her blood pressure is 100/70 mmHg. She has no significant past medical history and takes no medications.

Investigations:

Serum sodium 130 mmol/L (135-145)

Serum potassium 5.5 mmol/L (3.5-5.1)

Serum cortisol 100 nmol/L at 9 AM (171-536)

ACTH >200 pg/mL (10-60)

Which is the most likely diagnosis?