APPENDIX VIII: CORTICOSTEROIDS
These drugs mimic the action of the hormones produced by the outer layer (cortex) of the adrenal glands, a pair of small glands that sit on top of the kidneys. The main hormone produced is hydrocortisone (Cortisol) which has a variety of effects on the body. It controls the amount of sodium and potassium (‘salts’) that the kidney allows to pass into the urine, and releases glucose into the blood. Hydrocortisone also moves protein out of the muscles and bones, and influences the way fat is deposited. Finally it suppresses inflammation. In the case of asthma, it does so by damping down late-phase reactions (see p42), but in other inflammatory conditions the mechanism of action is probably more complex. This effect on inflammation makes corticosteroids useful in the treatment of allergic reactions, and in other diseases – such as rheumatoid arthritis, Crohn’s disease and ulcerative colitis – where inflammation plays a major role.
Because corticorsteroids have so many different functions in the body, there are various unpleasant side-effects from using them as drugs. These effects mainly occur when the drugs are taken by mouth. Long-term use of these drugs at high doses can result in Cushing’s Syndrome, characterized by deposits of fat around the face (‘moon face’), and on the shoulders and abdomen, water retention producing puffiness, bruising, acne, muscle wasting and weakening of the bones leading to easy breakage. In children, there is also stunted growth. All these changes are due to the effects of corticosteroids on other body processes, as described above. Some of the effects are reversible, if corticosteroids are withdrawn, but there can also be permanent damage.
In using corticosteroids to suppress allergic reactions, the trick is to persuade the drug to damp down inflammation without carrying out any of its other actions. This has been achieved, to a large extent, by modifying hydrocortisone and the other adrenal hormones chemically.
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