Cushing’s syndrome may be classified according to the source of cortisol into four subtypes; Endogenous, exogenous, familial Cushing’s Syndrome, and pseudo-Cushing’s syndrome.

Cushing’s syndrome is classified into two main subtypes:^[1][2][3]

• Exogenous:

• Also called iatrogenic Cushing’s syndrome. It is due to chronic glucocorticoid intake for inflammatory conditions, such as allergies, asthma, autoimmune diseases, and after organ transplantation.

• Endogenous:

• Benign tumors:

• Pituitary adenoma
• Adrenal adenoma
• Adrenal micronodular hyperplasia
• Ectopic adenomas, which are originated from locations other than the pituitary or adrenal glands, mostly from the lungs, pancreas, thyroid, or thymus.

• Malignant tumors:

• Adrenal cancer
• Cancer in places other than the pituitary or adrenal glands, mostly in the lungs, pancreas, thyroid, or thymus

• Familial Cushing’s Syndrome:

• Patients with rare genetic diseases like multiple endocrine neoplasia type 1 (MEN 1) and primary pigmented micronodular adrenal disease are more susceptible to develop tumors in glands that affect cortisol secretion. As a result, these patients will develop Cushing’s syndrome.

• Pseudo-Cushing’s Syndrome:

• It is due to alcoholism, depression or other psychiatric disorders, obesity, pregnancy, and poorly controlled diabetes.