FACTBOX-Olympics-Doping in sport

July 19 (Reuters) - Factbox on some of the main substances and methods used for doping in sport:

ERYTHROPOIETIN (EPO)

* EPO is a peptide hormone that is produced naturally by the human body. EPO is released from the kidneys and acts on the bone marrow to stimulate red blood cell production.

* By injecting EPO, athletes aim to increase their concentration of red blood cells and, consequently, their aerobic capacity. Health risks:

* EPO abuse can lead to serious health risks for athletes. It is well known that EPO, by thickening the blood, leads to an increased risk of several deadly diseases, such as heart disease, stroke, and cerebral or pulmonary embolism. Misuse of EPO may also lead to autoimmune diseases with serious health consequences. EPO has been implicated in the deaths of several athletes.

ANABOLIC STEROIDS

* Anabolic steroids are drugs that resemble testosterone, a hormone which is produced in the testes of males and, to a much lesser extent, in the ovaries of females.

* Because testosterone and related drugs affect muscle growth, raising their levels in the blood could help athletes to increase muscle size and strength. Athletes who use anabolic steroids also claim that they reduce body fat and recovery time after injury.Health risks:

* Anabolic steroids can cause high blood pressure, acne, abnormalities in liver function, alterations in the menstrual cycle in women, decline in sperm production and impotence in men, kidney failure and heart disease. They can also make both men and women more aggressive.

HUMAN GROWTH HORMONE

* Human growth hormone (hGH) - also called somatotrophin or somatotrophic hormone - is a hormone that is naturally produced by the body. It is synthesised and secreted by cells in the anterior pituitary gland located at the base of the brain.

* The major role of hGH in body growth is to stimulate the liver and other tissues to secrete insulin-like growth factor (IGF-1). IGF-1 stimulates production of cartilage cells, resulting in bone growth and also plays a key role in muscle and organ growth. All of these can boost sporting performance.Health risks:

* Commonly reported side effects for hGH abuse are diabetes in prone individuals, worsening of heart diseases, muscle, joint and bone pain, hypertension and cardiac deficiency, abnormal growth of organs and accelerated osteoarthritis.

SYNTHETIC OXYGEN CARRIERS

* Synthetic oxygen carriers, such as haemoglobin based oxygen carriers (HBOCs) or perflurocarbons (PFCs), are purified proteins or chemicals that have the ability to carry oxygen.

* They are useful for emergency therapeutic purposes when human blood is not available, the risk of blood infection is high or when there is not enough time to properly cross-match donated blood with a recipient. Health risks:

* The misuse of synthetic oxygen carriers for doping purposes carries the risk of cardiovascular disease in addition to serious side effects such as strokes, heart attacks and embolisms.

BLOOD TRANSFUSIONS

* There are two forms of blood doping. Autologous blood doping is the transfusion of one's own blood, which has been stored, refrigerated or frozen, until needed. Homologous blood doping is the transfusion of blood that has been taken from another person with the same blood type.

* Although the use of blood transfusions for blood doping dates back several decades, experts say its recent resurgence is probably due to the introduction of efficient EPO detection methods.

* A test for homologous blood transfusions was implemented at the 2004 Olympic Games in Athens and WADA is funding research projects aimed at developing a test for autologous transfusions. Health risks:

* Like the other forms of blood doping, transfusions can have serious medical consequences. Another person's blood may contain a virus, which is unwittingly passed on during the transfusion. An athlete who uses his or her own blood can put themselves at significant health risks if the procedure is not done properly or if the blood is not handled or stored in a proper manner. In addition, unnaturally high red blood cell levels increase the risk of heart attack, stroke, and pulmonary or cerebral embolism.

SOURCES: WADA/Reuters/ (Compiled by Kate Kelland; Editing by Clare Fallon)