A 52-year-old woman shows symptoms suggesting Addison's disease. What is the appropriate next diagnostic step?

In the case of a patient with symptoms suggestive of Addison's disease, the most appropriate next diagnostic step is to assess the adrenal function through the administration of hydrocortisone. Addison's disease, a primary adrenal insufficiency characterized by insufficient production of adrenal hormones (cortisol and often aldosterone), requires immediate attention to prevent adrenal crises and stabilize the patient.

Hydrocortisone is a synthetic corticosteroid that mimics the effects of cortisol, the hormone that is deficient in Addison's disease. Administering hydrocortisone not only helps manage the patient’s current symptoms—including fatigue, weight loss, and hypotension—but also serves as a therapeutic measure to prevent complications associated with adrenal insufficiency, such as an adrenal crisis. This crisis can occur if a person with undiagnosed or untreated Addison's disease is subjected to stress, illness, or surgery.

While hydration with saline can be necessary for a patient in adrenal crisis, the immediate provision of glucocorticoids like hydrocortisone is critical to directly address the underlying hormone deficiency and stabilize the patient. Oral glucocorticoids are typically used for long-term management once Addison's disease is confirmed and the patient is stable, while insulin therapy is unrelated to the management of adrenal