Letrozole (trade name Femara) is an oral aromatase inhibitor (AI) used in the treatment of hormonally responsive breast cancer after surgery. The FDA approved its use in post menopausal women who show hormone receptor positive types of breast cancer. It was banned in India in 2011 due to potential risk to infants when used in women who are pregnant; however, a Canadian study done by the American Society of Reproductive Medicine showed no evidence of birth defects. As a result, it remains legal in the rest of the world.
How does it work?
Similar to all aromatase inhibitors (AIs), letrozole, by binding to the aromatase enzyme, prevents estrogen from being released. It is known as a type II aromatase inhibitor.
It is the most powerful AI available; in fact, studies have shown it to drops estrogen levels in women by up to 98%. In men, clinical studies have shown a drastic reduction in estrogen levels very quickly of up to 65%. The main reason may be because it has the ability to crush estrogen through competitive/reversible binding to the heme of the relevant cytochrome P450 unit (protein enzyme).
Use in Bodybuilding
Since letrozole is such a powerful AI, it can be a great weapon to combat emergency situations, where estrogen related sides get out of control. When an anabolic steroid user uses compound such as testosterone, dianabol, deca durabolin, equipoise etc; they will aromatize in the body and convert to estrogen. This can result in multiple estrogen side effects such as water retention, which has a domino effect and can effect your libido, sleep, blood pressure, and energy. Another dangerous estrogen side effect is gynecomastia (bitch tits), which, if left untreated, can require expensive and invasive surgery. For this reason, it is crucial to run an aromatase inhibitor if you use aromatizing steroids during your cycle.
Negative Side Effects
There is such a thing as too much in the bodybuilding world, and, when it comes to AI’s, letrozole definitely fits that bill. Although, as males, we view estrogen as a female hormone, that does not mean we don’t need it in our system to properly function. After all, estrogen helps males grow muscles! Low estrogen can cause depression, effect mood, hurt the immune system and lower libido. Since letro is so powerful at dropping estrogen levels, you must be careful not to abuse this drug. You should always keep it on hand for emergencies; in fact, always have it on hand before running a cycle. View it as a rainy day f