The hypothalamic-pituitary-adrenocortical system. Clinical evaluation by pharmacologic techniques.

The hypothalamic-pituitary-adrenocortical system is a complex negative feed-back control mechanism. Under non-stress conditions it functions to maintain a circadian rhythm of adrenal steroid production which is secondary to a circadian fluctuation in the sensitivity to suppression of acth by hydrocortisone. Any stressful stimulus causes an augmentation of steroid production which is due in part to a decrease in sensitivity of acth to suppression. Aldosterone production is not primarily controlled by acth. The increased understanding of this system and of its pathologic alterations has led to the development of a number of pharmacologic techniques which have proved most valuable in evaluating its integrity. Hypothalamic-pituitary function can be assessed by the response to the administration of dexamethasone, methopyrapone, bacterial pyrogen and vasopressin. Adrenal cortical function can be assessed by the response to acth, dexamethasone and spironolactone.