A 40-year-old alcoholic man is being treated for tuberculosis, but he has been only intermittently compliant with his medications despite the health department's best efforts at directly observed therapy. He complains of increasing weakness, fatigue, weight loss, and nausea over the preceding 3 weeks. He appears thin, and his blood pressure is 80/50 mm Hg. There is increased pigmentation over the elbows and in the palmar creases. Cardiac examination is normal. Which of the following is the best next step in evaluation?

This patient's symptoms of weakness, fatigue, and weight loss in combination with hypotension and extensor hyperpigmentation are all consistent with adrenal insufficiency (Addison disease). Tuberculosis can involve the adrenal glands and result in adrenal insufficiency. Measurement of serum cortisol baseline and then stimulation with cosyntropin (a synthetic ACTH analogue) will confirm the clinical suspicion. The cosyntropin stimulation test is used to determine the adrenal reserve capacity for steroid production. Cortisol response is measured 30 and 60 minutes after cosyntropin is given intramuscularly or intravenously; a value of 18 mg/dL or above effectively excludes adrenal insufficiency. ACTH level (drawn before cosyntropin administration) will demonstrate whether the problem is based in the adrenal gland (primary) or hypothalamus/pituitary axis (secondary). Hemochromatosis can cause hyperpigmentation but not the weight loss and hypotension. Bacteremia would not cause the gradually increasing symptoms or the hyperpigmentation. In some patients with weight loss and nausea, an esophagogastroduodenoscopy (EGD) may be warranted; however, the clinical features of adrenal insufficiency in conjunction with poorly treated tuberculosis would first direct attention toward adrenal status.