Adrenal failure: A condition in which the adrenal glands do not produce enough of the adrenal hormones that control important functions such as blood pressure.
The adrenal glands sit on top of the kidneys. The adrenal is made up of an outer layer (the cortex) and an inner portion (the medulla). The adrenal glands produce hormones that help control the heart rate, blood pressure, the way the body uses food, and other vital functions. The adrenal cortex secretes steroid (cortisone-related) hormones and mineralocortoids that regulate the levels of minerals such as sodium and potassium in the blood.
The adrenal medulla makes adrenaline (epinephrine) and noradrenaline (norepinephrine). Adrenaline is secreted in response to low blood levels of glucose as well as exercise and stress; it causes the breakdown of the storage product glycogen to the sugar glucose in the liver, facilitates the release of fatty acids from adipose (fat) tissue, causes dilation (widening) of the small arteries within muscle and increases the output of the heart. Noradrenaline is a neurohormone, a neurotransmitter, for of most of the so-called sympathetic nervous system.
The term "Addison's disease" refers to long-term insufficiency of the adrenal cortex. This may be due to a number of different insults to the adrenal including physical trauma, hemorrhage, and tuberculosis of the adrenal, and destruction of the cells in the pituitary gland that secrete ACTH (adrenocorticotropic hormone) which normally drives the adrenal. Addison's disease is characterized by bronzing of the skin, anemia, weakness, and low blood pressure. The U.S. President John F. Kennedy had Addison's disease. The condition is named after the British physician Thomas Addison (1793-1860).