The causes of Cushing syndrome may include which of the following?

b. Adrenal hyperplasia

c. Small cell lung carcinoma

e. Adrenal carcinoma 

The varied causes of cortisol excess produce clinical features that are collectively called Cushing syndrome. These include exogenous steroid administration, Cushing disease (excessive ACTH production by the anterior pituitary gland, usually from an adenoma), ectopic ACTH production (small cell lung carcinoma), adrenal adenoma or carcinoma, micronodular pigmented hyperplasia, macronodular hyperplasia, and steroid-dependent adrenal hyperplasia. Pheochromocytoma is characterized by catecholamine rather than cortisol excess as it arises from the adrenal medulla rather than the adrenal cortex.