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The body has two adrenal glands, one near the top of each kidney. The inner part (medulla) of the adrenal glands secretes hormones, such as adrenaline (epinephrine) that help control blood pressure, heart rate, sweating and other activities regulated by the sympathetic nervous system. The outer part (cortex) secretes different hormones, including corticosteroids and mineralocorticoids, particularly aldosterone, which controls blood pressure and the levels of salt and potassium in the body. The adrenal glands also play a role in stimulating the production of androgens.
The adrenal glands are controlled in part by the brain. The hypothalamus, a small gland in the brain involved in hormonal regulation, produces corticotropin-releasing hormone and vasopressin. These two hormones trigger the pituitary gland to secrete corticotropin, which stimulates the adrenal glands to produce corticosteroids. The renin-angiotensin-aldosterone system, regulated mostly by the kidneys, causes the adrenal glands to produce more or less aldosterone.
The body controls the levels of corticosteroids according to need. The levels tend to be much higher early in the morning than later in the day. When the body is stressed from illness or otherwise, the levels of corticosteroids increase dramatically.