The adrenal glands, located atop each kidney, are divided into two distinct regions: an outer cortex and an inner medulla (Fig. 1). The hormones produced by this gland are involved in the body's response to stress. The cortex produces steroid hormones, cortisol, aldosterone, and small amounts of sex hormones. Cortisol (hydrocortisone) mobilizes reserves of fats and carbohydrates to increase the levels of these nutrients in the blood. It also acts to reduce inflammation and is used clinically for this purpose. Aldosterone acts on the kidneys to conserve sodium and water while eliminating potassium. The adrenal cortex also produces small amounts of sex hormones, mainly testosterone, but their importance is not well understood.

The medulla of the adrenal gland produces two similar hormones, epinephrine (adrenaline) and norepi-nephrine (noradrenaline). These are released in response to stress and work with the nervous system to help the body meet challenges.

FIGURE 1. (A) The adrenal glands on top of each kidney. (B) Each adrenal gland is divided into a medulla and cortex, each secreting different hormones.

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