POMC and adrenal gland hyperfunction: A rapid decrease in the level of cortisol, ACTH, and metanephrines upon initiation of metyrapone treatment suggests the existence of a glucocorticoid-dependent positive feedback loop that potentiated ACTH release and created a destructive cycle with rapid exacerbation of both hypercortisolemia and hypercatecholaminemia, with extremely elevated plasma ACTH levels.