AI (Aromatase inhibitors):Which is the best anti-estrogen to take on a steroid cycle

The three most commonly used AI are letrozol, arimidex and exemestan, which AI should I choose when I want to block the effects of estrogen.

Which one lowers more estrogen

If the purpose is to block the effect of estrogen, then which AI can reduce the level of estrogen to a greater extent, then it is better, right?

Let’s look at how these three AI reduce estrogen levels. Studies have shown that Letrozol can reduce estrogen levels by 98 percent. arimidex can reduce estrogen levels by 50-60%, a percentage that accumulates if used consistently. Exemestan can reduce estrogen levels by 58±21%.

From the above data, letrozol is the more effective one. So letrozol was the first choice of the three AI, right? The answer is not so. Let’s keep looking down.

Different object

Although they all works to reduce estrogen levels, the three AI’s target objects are different. The target of letrozol and arimidex is the estrogens transformed by aromatase, while the target of exemestan is aromatase and all estrogens attached to aromatase.

Aromatase converts testosterone into estrogen, and excess estrogen accumulation produces corresponding estrogen side effects. Letrozol and arimidex do not act on the aromatase and bind to the estrogen converted by the aromatase, so that this part of the estrogen cannot work. Exemestan differs from them in that it directly interacts with aromatase, killing the aromatase as well as the estrogens attached to the aromatase.

Their different ways of acting make them a clear difference after use: at the end of the cycle, AI stops using, and the estrogen accumulated during this period is suddenly released, estrogen levels surge, and high estrogen symptoms are more likely to occur. Unlike using exemestan, which kills the aromatase, even after stopping using exemestan at the end of the cycle, it takes some time for the body to recover the original aromatase levels, so your estrogen levels will always be low.

From this perspective, it is clearly better for exemestan to lower estrogen levels. So, should you choose exemestan? Let’s keep looking down.

Role of estrogen

Is lower estrogen the better? Not really. Estrogen levels have an impact on libido, mood, skin quality, hair, nails, bone health and more. Low estrogen levels can lead to stiff joints, loss of sex drive, drowsiness and more. So it’s not about lowering estrogen levels as low as possible.

So, of the three AI’s, the one most commonly used to reduce estrogen levels during the cycle is arimidex, especially for novices. For the experienced, of course, there are other options, such as exemestan. Although it kills aromatase, it lowers estrogen levels by 58±21% and also increases total and free testosterone levels, making it a good option for bodybuilders to gain muscle mass if they can control the dose and frequency of exemestan use. Since letrozol reduces estrogen levels by 98% and is really very effective, it is not usually used for cycle, but to reverse gyno symptoms that have already occurred.