The most common cause of Cushing's syndrome is:
d. Iatrogenic steroids(Ref: Nelson's 20/e p 2227-2729, Ghai 8/e p 525)The most common cause of Cushing's syndrome is prolonged exogenous administration of glucocorticoid hormones, especially at the high doses used to treat lymphoproliferative disorders.
Pituitary adenoma
Adrenal adenoma
Ectopic ACTH
Iatrogenic steroids
Endocrinology