POMC and adenoma: Inferior petrosal sinus sampling (IPSS) is used to distinguish pituitary ACTH‐dependent Cushing disease (CD) from ectopic ACTH‐dependent syndrome (EAS) after ACTH‐dependent hypercortisolism is confirmed biochemically and no adenoma or an adenoma <6 mm is detected on MRI.4, 5, 6, 7