Estrogens are produced by the conversion of androgens through the activity of the aromatase enzyme. Letrozole blocks the production of estrogens in this way by competitive, reversible binding to the heme of its cytochrome P450 unit. It is important to note that letrozole does not decrease the production of mineralocorticoids or corticosteroids. In contrast, the antiestrogenic action of tamoxifen, the major medical therapy prior to the arrival of aromatase inhibitors, is due to its interfering with the estrogen receptor, rather than inhibiting estrogen production. Side effects include signs and symptoms of hypoestrogenism. There is concern that long term use may lead to osteoporosis, which is why prescriptions of Letrozole are often accompanied by prescriptions of osteoporosis-fighting medication such as Fosamax. Letrozole has also been shown to delay the fusing of the growth plates in adolescents. This may boost the effectiveness of growth hormone, and thus Letrozole is used to treat adolescents and children with short stature. Letrozole has shown to reduce estrogen levels by 98 percent while raising testosterone levels. The anti-estrogen action of letrozole is preferred by athletes and bodybuilders for use during a steroid cycle to reduce bloating due to excess water retention and prevent the formation of gynecomastia related breast tissue that is a side effect of some anabolic steroids. Usage above 2.5 mg/day is known to potentially temporarily kill sex drive. Above 5mg/day for extended periods may cause kidney problems.
Letrozole in particular cannot be categorized into the three tiers of users (beginner, intermediate, and advanced) as normally outlined and listed in common profiles of the different compounds and drugs. This is due to the fact that Letrozole is an ancillary drug not particularly used for the purpose of performance enhancement, but instead is utilized to combat or mitigate various Estrogen-related side effects when aromatizable anabolic steroids are utilized.
In some instances, Letrozole doses might possibly also be utilized to increase the endogenous secretion of Testosterone in men, which allows this compound to be utilized as an ancillary medication during PCT (Post Cycle Therapy) phases following the end of an anabolic steroid cycle, but its use on its own for this purpose is not very common and is unlikely to produce noticeable performance enhancing effects. Letrozole’s use as an endogenous Testosterone stimulating agent will be further covered in detail shortly.
For the purpose of Estrogen control during a cycle: Letrozole is the most effective aromatase inhibitor utilized to reduce levels of circulating Estrogen in the body during a cycle involving the use of aromatizable androgens (anabolic steroids that have an affinity to bind to the aromatase enzyme and undergo aromatization into Estrogen). This has been outlined previously in the introduction. Letrozole doses for this purpose cover a very wide range, and how much Letrozole is required (and how often) is also largely dependent on the doses of aromatizable anabolic steroids used, the individual’s sensitivity to aromatase inhibitors, and the rate of aromatization of the anabolic steroids used. With this being said, the general range of Letrozole doses are approximately 1.25mg-2.5mg daily. There does exist a very large margin for adjustment and user preference when it comes to Letrozole dosages, as each individual should slowly adjust their dose depending on how they feel the body is responding. This is especially so for Letrozole, which is the most powerful and potent AI of the three. Even 1.25mg daily is too much for many anabolic steroid users, and often times the recommended dose is actually 1.25mg every other day, and often can be even less frequent especially considering the half-life of Letrozole is that of 2-4 days. These Letrozole doses can easily be adjusted if the user feels it is not working well enough, or if it is reducing Estrogen levels too much.
Because Letrozole is by far the most effective aromatase inhibitor with the ability to reduce Estrogen levels to undetectable levels, users must be cautious to ensure that these Estrogen levels do not plummet too low to be considered healthy. As Estrogen levels decline, the physique may take on more of a harder “grainier” and “ripped” look due to the loss of water retention provided by Estrogen. This results in very little to no subcutaneous fluid, which will present the underlying musculature more prominently. The one exception to the issue of complete Estrogen elimination is in competitive bodybuilders that require almost total elimination of water retention on the competition day. In such a situation, Letrozole might possibly be the best aromatase inhibitor to use above all other AIs at a full dose utilized by a competitive athlete only days leading up to a competition for the physique altering reasons previously stated. Near-total reduction of Estrogen should not be maintained for more than a 48 hour period for health reasons.