Want to know more about drugs, blood and sports performance?

Just search the Internet. Here's something interesting: Various other factors can affect the rate of erythropoiesis by influencing erythropoietin production. Thyroid hormones, thyroid-stimulating hormone, adrenal cortical steroids, adrenocorticotrophic hormone, and human growth hormone (HGH) all promote erythropoietin formation and so enhance red blood cell formation (erythropoiesis). In thyroid deficiency and anterior pituitary deficiency, anaemia may occur due to reduced erythropoiesis. Polycythaemia (excess red blood cell production) is often a feature of Cushing's syndrome. However, very high doses of steroid hormones seem to inhibit erythropoiesis. Androgens (male hormones) stimulate and oestrogens (female hormones) depress the erythropoietic response. In addition to the effects of menstrual blood loss, this effect may explain why women tend to have a lower haemoglobin concentration and red cell count than men. Plasma levels of erythropoietin are raised in hypoxic conditions (low oxygen levels). This produces erythrocytosis (increase in the number of circulating erythrocytes) and the condition is known as secondary polycythaemia.

What's it all mean? Well...

1. erythropoiesis is essentially the production of red blood cells, and the more you have of those babies the better your oxygen transport capacity
2. erythropoietin or EPO is the substance that triggers production of red blood cells - the more EPO you have the more red blood cells are triggered to mature in the bone marrow
3. EPO production is normally in your kidneys but lately pharmaceutical companies have built factories to make it as well, for medicinal reasons only, of course
   
4. Thyroid hormones, thyroid-stimulating hormone, adrenal cortical steroids (like glucocorticosteroids or Prednisone) , adrenocorticotrophic hormone, and human growth hormone (HGH) all promote erythropoietin formation, which again means more red blood cells in your blood; however before you all rush off to secure illegal supplies of banned substances let's note that the side-effects of these substances on otherwise healthy people will vary from catastrophic to dangerous, and in fact...
   
5. Very high doses of steroid hormones (whatever that means - 50-60mg/day, perhaps of a cortico-steroid?) "seem" to inhibit erythropoiesis, which is to say lower your red cell production and release - and is thus not very good for your bike riding, is it?
   
6. Androgens (ie male hormones, popularly known as the body-building 'steroids' but not to be confused with the stress-response-related and ultimately body-destroying cortico-steroids) stimulate red blood cell production. Great if you are guy, eh? You get big muscles and more red cells just for being born with significant external genitalia! Yippee!
   
7. And the female hormones - the oestrogens - depress the erythropoietic response and lower your red blood count. Not so good for the girls, especially when your balance of hormones changes during the menstrual cycle - which could mean fewer blood cells just when you need 'em
8. Plasma levels of erythropoietin are also raised in hypoxic conditions, which is to say your red blood cell counts go up when you reduce oxygen availability. Naturally this occurs at higher altitudes (like on top of mountains), so you get more aerobic transport capacity in thinner air (which makes sense) but some athletes have been known to simulate this with specially-designed tents that reduce the oxygen content as you sleep; so after a few weeks of acclimatization you wake up with an markedly increased aerobic ability. Some say this is cheating and have outlawed it; others think it's OK and a lot cheaper than travelling to a high-altitude environment and staying there for a month or more...
   
9. And of course blood doping is simply injecting yourself with pre-removed blood, either from yourself or others. It's obviously all a bit risky and involves a cascade of un-natural responses as your body tries to deal with a suddenly elevated volume of blood, but for a little while you have more red cells and more aerobic transport capacity. If you don't die first of course.
   

Now it doesn't make me a doctor of medicine but hopefully it makes more sense now, doesn't it?