The human adrenals are located in close vicinity to the upper kidney poles. The weight of the adrenals in adults is approximately 4g and is not affected by age, body weight or sex. The adrenal consists of two functionally distinct endocrine glands, which are covered by a common capsule. The adrenal cortex is the outer layer of the adrenal gland and makes up approximately 90% of the adrenal weight. In the cortex, adrenal steroids such as the stress hormone cortisol, the blood pressure hormone aldosterone and adrenal androgens are produced.
The adrenal medulla is located in the inner part of the adrenal gland. Here, the catecholamines epinephrine and norepinephrine are produced.
Both parts of the adrenal gland play an essential role in adaptation to major stress. In response to severe infection, trauma and shock, the organism responds with activation of the adrenal gland, leading to enhanced cortisol (glucocorticoid) secretion and catecholamine secretion. This response is necessary to maintain homeostasis during stress. In case of adrenal impairment, the stress response will be severely diminished which may ultimately lead to irreversible shock.