The effect of ACTH is rapid, occurring within a few minutes. The release of ACTH, leading to the secretion of cortisol and androgen, occurs episodically throughout the twenty-four-hour cycle in a circadian pattern. ACTH release occurs in response to low circulating levels of cortisol (as in Addison's disease) and is inhibited by high circulating levels of cortisol or synthetic glucocorticoids (as in corticosteroid therapy). This negative feedback probably occurs at hypothalamic and pituitary sites. ACTH is also released in response to stress (such as trauma, surgery, anxiety and emotional disturbance).
