Erythropoietin — a hormone that triggers the production of red blood cells, became known to the general public in the 1990s because of its connection to scandals in professional sports: it was used as doping.
The hormone was of interest to athletes because of its ability to stimulate the production of new red blood cells from stem cells in the bone marrow. The more red blood cells in the blood, the more oxygen molecules are delivered throughout the body per heartbeat. Improved oxygen supply has a direct impact on an athlete's performance: they can train longer and harder.
Not everyone knows, however, that the body can naturally produce more red blood cells through a small lack of oxygen, such as during interval hypoxic training or high altitude training.
From 85 to 90% of erythropoietin is formed in the kidneys, and 10–15% — in the liver. In the body of the child in the womb, the opposite ratio is observed. Very small amounts of EPO are also produced in the brain, uterus, testicles and spleen.
When the oxygen content of the blood is low or the number of red blood cells is insufficient, the cortical substance of the kidneys produces more erythropoietin. From there it is transported by the bloodstream to its site of action.
Individual variation in the formation of EPO is absent, and there is no difference between women and men in terms of the effect of increasing the concentration of EPO in the blood. However, during the day, EPO levels fluctuate: in the morning they reach their lowest values.
Effect of erythropoietin
A healthy person produces about 3 million new red blood cells per second. Erythropoietin is transported by the bloodstream into the bone marrow where it stimulates the formation of red blood cells from stem cells — this is called erythropoiesis. This process is provided by various hormones, including testosterone, which promotes the maturation of blood cells in the bone marrow. It is in the male body that there are more red blood cells compared to the female body. Consequently, men have higher levels of hematocrit and hemoglobin.
In a sudden spike in EPO production, such as during interval hypoxic exercise, it takes 3-4 days for young red blood cells to form in the bone marrow and get into the bloodstream.The formation of new red blood cells — this is not the only function of erythropoietin. Throughout the body there are cells with an EPO receptor: they respond differently to erythropoietin. For example, EPO protects some nerves and heart muscles from death. In the vascular system, the response of endothelial cells is very similar to that of bone marrow stem cells. This produces new cells that are involved in repairing vascular damage and forming new blood vessels.
Prospective trend in medicine
Today, many scientists are investigating the effects of EPO in the treatment of Alzheimer's and Parkinson's disease, as well as for recovery from heart attack and stroke. There is evidence that erythropoietin may also provide protection against the severe course of coronavirus infection with a risk of death.
While erythropoietin has gained a negative reputation in the past, its natural production through hypoxic exercise has positive effects on the human body. Moreover, hypoxic therapy is not considered a doping and thus can be used freely among athletes. And the potential use of EPO in medicine makes it a promising means to improve people's lives.