Adrenal insufficiency can be divided into primary and secondary according to the cause, and can be divided into acute and chronic according to the course of the disease. The most common primary adrenal insufficiency is Addison's disease, whose common causes are adrenal tuberculosis or autoimmune adrenalitis; rare causes include deep fungal infection, immunodeficiency, viral infection, malignant tumors, extensive adrenal hemorrhage, surgical resection, adrenoleukodystrophy and POEMS disease. Secondary adrenal insufficiency is most commonly caused by long-term use of supraphysiological doses of glucocorticoids, and can also be secondary to hypothalamic-pituitary diseases, such as sellar tumors, autoimmune hypophysitis, trauma, surgical resection, and postpartum hemorrhage causing large-area pituitary infarction and necrosis, namely Sheehan syndrome.