A 34-year-old woman presents to the clinic with a 6-month history of increasing fatigue, muscle weakness, and unintentional weight loss. She has also noticed darkening of her skin, especially around her elbows, knees, and knuckles. The patient mentions feeling dizzy when standing up quickly, which has become more pronounced in the last few weeks. She reports a loss of appetite and occasional nausea. Additionally, she has been experiencing some irritability and difficulty managing stress at work.

The patient has no significant past medical history and is not taking any medications. She denies any recent illness, but she did experience a significant emotional stressor a few months ago, which she believes may have contributed to her current symptoms.

On physical examination, the patient appears fatigued. Her blood pressure is 90/60 mmHg, and her heart rate is 88 beats per minute. There is noticeable hyperpigmentation on her skin, particularly over the hands, elbows, and posterior neck. The rest of her physical exam is otherwise unremarkable.

Laboratory results reveal the following:

Sodium: 132 mmol/L (Low)

Potassium: 5.4 mmol/L (High)

Random cortisol level: 3 µg/dL (Low)

ACTH level: 200 pg/mL (High)

Plasma renin activity: elevated

Given the clinical signs of fatigue, skin changes, hypotension, electrolyte abnormalities, and laboratory findings, the diagnosis of Addison’s disease is suspected.