This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
True about Cushing’s syndrome is 
Select and explain. 
A. Most common cause is excess ACTH, B. High plasma levels of ACTH and cortisol, C. Also referred as Hyperadrenalism, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Hyperadrenalism—Cushing’s Syndrome
Hypersecretion by the adrenal cortex causes a complex cascade of hormone effects called Cushing’s syndrome. Many of the abnormalities of Cushing’s syndrome are ascribable to abnormal amounts of cortisol, but excess secretion of androgens may also cause important effects. Hypercortisolism can occur from multiple causes, including (1) adenomas of the anterior pituitary that secrete large amounts of ACTH, which then causes adrenal hyperplasia and excess cortisol secretion; (2) abnormal function of the hypothalamus that causes high levels of corticotropin-releasing hormone (CRH), which stimulates excess ACTH release; (3) “ectopic secretion” of ACTH by a tumor elsewhere in the body, such as an abdominal carcinoma; and (4) adenomas of the adrenal cortex. When Cushing’s syndrome is secondary to excess secretion of ACTH by the anterior pituitary, this is referred to as Cushing’s disease.
Excess ACTH secretion is the most common cause of Cushing’s syndrome and is characterized by high plasma levels of ACTH and cortisol.