Cortisol hormone molecule. Computer model of a molecule of the steroid hormone cortisol. Atoms are represented as blobs and are colour-coded: carbon (bronze), hydrogen (green) and oxygen (blue). Cortisol is produced by the adrenal glands, which sit on top of the kidneys. It is produced in response to stress and increases blood pressure, blood sugar levels and suppresses the immune system. Due to its effect on the immune system cortisol is also used in medicine, when it is referred to a hydrocortisone, to treat allergies and as an anti-inflammatory.