This essay will explain the hormone erythropoietin, its effects and its role in the professional sports industry. Explaining what erythropoietin is, the process of erythropoiesis, its role in the body, its side effects versus benefits, and its role in modern sport will form the basis of this essay. With the conclusion of this essay my view will be that natural erythropoietin is an integral part of homeostasis and that synthetic erythropoietin should only be used for specific medical conditions rather than as a performance enhancer in professional sport. Natural erythropoietin is found mainly in the kidneys and liver and is used to regenerate red blood cells present in the red bone marrow (Heuberger et al. 2013). Because red blood cells have no nucleus or cellular components, they only have a short lifespan of approximately 120 days before erythropoietin is needed to regenerate more using the process of herthropoiesis (Heuberger et al. 2013). Erythropoietin also has uses in protecting neural activity and the blood brain barrier (Noguchi et al. 2007), however these factors will not be discussed in this essay. The process by which erythropoietin regulates the production of red blood cells is called erythropoiesis. When the kidneys and liver detect hypoxia in the blood, erythropoietin is released which stimulates the red bone marrow to increase the production of red blood cells allowing for greater transport of oxygen through the bloodstream (Martini, Ober & Nath 2014). The diagram below illustrates the cycle of erythropoiesis as oxygen levels in the bloodstream rise and fall. Figure 10.6 (Marieb & Hoehn 2010, p. 338). To help people suffering from chronic anemia, a synthetic version of erythropoietin called r-HuEPO was produced, despite demonstrating... halfway through the document... this resulted in many cyclists being banned from practicing this sport, in particular those Lance Armstrong in 2012. In this essay, five points were presented that highlighted what erythropoietin is, how it works, what its benefits are versus potential side effects, and its overall use in professional sports. Its function as a producer and regulator of red blood cells is essential to ensure that our muscles, organs and brain always receive enough oxygen and nutrients. The invention of an artificial version of erythropoietin ensured a viable treatment for some conditions but also opened up the possibility of unethical use in sport. The health risks of using r-HuEPO, especially long-term, mean that its risks far outweigh any perceived minor benefits for athletes and as such it should only be used for prescribed medical reasons.