What is it?
Cortisol is a steroid. It belongs to a group of steroids called glucocorticoids because they affect blood sugar (glucose) levels in the blood. Cortisol is produced in the body by the adrenal glands. These are two triangular shaped glands that lie on the top of each kidney.
The amount of cortisol produced is controlled by two other hormones, corticotrophic releasing hormone (CRH) and adrenocorticotrophic hormone (ACTH). CRH is produced by the hypothalamus, which is an area on the underside of the brain, and ACTH is produced by the pituitary gland that hangs just under the brain and is connected to the hypothalamus.
When CRH increases, more ACTH is released into the blood and this causes more cortisol to be secreted by the adrenal glands. As cortisol increases one of the things that happens is that it is carried back in the blood to the hypothalamus and pituitary and lowers the amount of CRH and ACTH being secreted. This balance of hormones is upset if an excessive amount of one of these hormones , for example by a tumour, is released into the blood. (See Cushing’s syndrome and Addison's disease).
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