It is usually random. A very small number of families carry genes for men, type 1 (multiple endocrine neoplasia), that makes them more likely to have pituitary tumors, including the type that over-produces in acth and causes cushing's disease. But other than these families, everyone is at equal risk for this condition.
Rare. Cushing's disease is a rare hormonal problem caused by a tumor in a small gland that sits above the kidneys called the adrenal glands. It can occur without any clear cause or in people who inherit certain genetic mutation. There are no clear lifestyle factors or environmental exposures that cause cushing's disease.