In the alcoholic patient with pseudo-Cushing's, admission to hospital (and avoidance of alcohol) will result in normal midnight cortisol levels within five days, excluding Cushing's
Another cause for Cushing's syndrome is the extremely rare form of cancer (Adrenal Cortisol Carcinoma), when a benign lesion on the adrenal gland (which would cause Cushing's) becomes malignant and starts producing its own cortisol. This produces Cushing's-like symptoms and is fatal. Life expectancy depends on early detection. Ruling out ACC is done with a CT scan of the abdomen, identifying the size and location of adrenal tumors and lesions.
^Newell-Price J, Trainer P, Besser M, Grossman A. (1998). "The diagnosis and differential diagnosis of Cushing's syndrome and pseudo-Cushing's states.". Endocr Rev19 (5): 647–72. doi:10.1210/er.19.5.647. PMID9793762.