Adrenal glands

Adrenal glands, or suprarenal glands, small endocrine glands closely attached to the upper part of each kidney, each comprising a central medulla and a surrounding cortex. The adrenal medulla secretes the hormones epinephrine (adrenaline) and norepinephrine. Release of these hormones follows stress-related stimuli such as pain, emotional disturbance, hypotension (low blood sugar), exposure to severe cold, and muscular exertion. The adrenal medulla is not essential to life; a person can survive in good health after total removal of the glands if adequate substitution therapy is provided. The adrenal cortex secretes about 30 steroid hormones that are separated into 3 main groups. The glucocorticoids, including cortisol, enhance glucose formation in the tissues and cells. The mineralocorticoids, including aldosterone, are steroids that promote retention of sodium and excretion of potassium by the kidney. The androgens are sex hormones that have a weaker effect than those produced by the (male) testes and (female) ovaries. Disorders of the adrenal cortex, such as Addison's disease or Cushing's syndrome, may be due to either defective or excessive secretion of hormones.

See also: Epinephrine; Gland; Hormone.