The correct option is A ACTH
Addison's disease is caused by under secretion of ACTH (Adrenocorticotropic hormone). It is produced by the pituitary glands. It stimulates the adrenal glands to produce the hormone cortisol. Cortisol stimulates gluconeogenesis and maintains blood pressure. If ACTH output is too low, cortisol production is lowered. Eventually, the adrenal glands shrink due to lack of ACTH. Thus the correct answer is option A.