Primary adrenal insufficiency is most commonly caused by autoimmune adrenalitis. Often called Addison disease, primary adrenal insufficiency is rare, with global prevalence estimates ranging from 4 to 221 cases per 1 million. Secondary adrenal insufficiency, which is characterized by decreased pituitary gland production of corticotropin, occurs globally in 140 to 279 per 1 million individuals. Most patients with primary adrenal insufficiency and secondary adrenal insufficiency have months to years of nonspecific symptoms before diagnosis, and up to 50% experience an adrenal crisis. ➡️ Learn more about the pathophysiology of adrenal insufficiency and approaches to diagnosis, treatment, and prevention of adrenal crisis in this JAMA Review: ja.ma/445xGCy