Primary adrenal insufficiency, also called Addison's disease, occurs when adrenal gland production of cortisol is chronically deficient, resulting in chronically elevated ACTH levels; when a pituitary tumor is the cause of elevated ACTH (from the anterior pituitary) this is known as Cushing's Disease and the constellation of signs and symptoms of the excess cortisol (hypercortisolism) is known as Cushing's syndrome. A deficiency of ACTH is a cause of secondary adrenal insufficiency. ACTH is also related to the circadian rhythm in many organisms.
Functional adrenocorticotropic hormone–secreting pituitary adenomas (ACTH-PAs) secrete inappropriate amounts of ACTH, which results in disorderly and excessive production of cortisol by the adrenal gland 1).
Nonfunctioning pituitary macroadenoma (NFMA) patients suffer from altered sleep-wake rhythmicity. Hydrocortisone dependency may explain part of the decreased daytime functioning, but the independent influence of visual field defects (VFD) and differences between Addison's disease (AD) and NFMA patients point towards a role for dysfunction of the adjacent suprachiasmatic nucleus (SCN) 2).