A little background info on Estrogen Control:
When looking to control Estrogen, we have two choices. These are SERMS and AI's. SERM is an acronym for Selective Estrogen Receptor Modulator, and AI is an acornym for Aromatase Inhibitor.
Let's take a look at what SERM's do and our SERM options. SERM's, by definition, compete for the space that Estrogen binds to. This receptor is then full and cannot accept the estrogen and therefore cannot produce the effects of estrogen. Some of the more popular SERM's are: Clomiphene Citrate (Clomid), Tamoxifen (Nolvadex), Toremifene Citrate (Fareston), and Raloxifene hydrochloride (Evista).
Now let's look at some of the AI's and how they work. AI's, by definition, prevent aromatizable steroids from converting to Estrogen via the aromatase enzyme. Some are more effective than others. Some of the more popular ones are: Anastrozole (Arimidex), Aromasin (Exemestane), and Letrozole (Femara).
So what are some facts and uses of the different SERM's and AI's?
Well, some AI's take time to build up blood levels and therefore need to be utilized for a certain time before they are effective, whereas SERM's go to work immediately.
Comid: Usually dosed from 25-300 mgs depending on the desired effect, is both effective during a cycle for estrogen sides and post cycle for support of natural Testosterone levels. While it has been claimed that Clomid "stimulates" production of LH and therefore of testosterone, in fact Clomid's activity is achieved not by stimulation of the hypothalamus and pituitary, but by blocking their inhibition by estrogen.
Clomid is a mixed estrogen aganoist/antagonist (activator/blocker) which, when bound to the estrogen receptor, puts it in a somewhat different conformation (shape) than does estradiol. The estrogen receptor requires binding of an estrogen or drug at its binding site and also the binding of any of several cofactors at different sites. Without the binding of the cofactor, the estrogen receptor is inactive.
Different tissues use different cofactors. Some of these cofactors are able to bind to the estrogen receptor/Clomid complex, but others are blocked due to the change in shape. The result is that in some tissues Clomid acts as an antagonist -- the cofactor used in that tissue cannot bind and so the receptor remains inactive -- and in others Clomid acts as an agonist (activator), because the cofactors used in that tissue are able to bind. Clomid is an effective antagonist in the hypothalamus and in breast tissue. It is an effective agonist in bone tissue, and for improving blood cholesterol.
Clomid also has the property of reducing the adverse effect of exercise-induced damage of muscle tissue. This is very significant for endurance athletes but is not very significant, if at all significant, with reasonable weight training. Clomid does not perceptibly affect gains of the weight trainer either favorably or adversely in my experience.
It should also be noted that Clomid seems to have estrogenic effects on mood, causing some slight depression or moddiness. It can also effect eyesight by causing it to seem blurry. No this isn't from crying while listening to James Blunt CD's. LOL
Nolva: Usually dosed from 10-100 mgs, Nolva is best dosed at 20-40 mgs. It has a certain affinity for binding to breast tissue receptors that Clomid doesn't. It can significantly raise Testosterone levels. However, it can reduce IGF-1 levels. It is commonly said that Nolva can accomplish at 20 mgs what Clomid can at 150mgs. Something to keep in mind. Nolva does not decrease the bodies LH response to LHRH like Clomid can. It can reduce the blood levels of Arimidex and Letro rendering them less effective. It does not affect Aromasin.
Evista: Evista is a second-generation SERM. It is approved by the FDA for this use in women. Although it bears structural and mechanistic similarities to other SERMs which have been approved either as fertility drugs (Clomid) or Breast Cancer medication (Nolvadex), it has not been approved for either of those uses. Ralixofene exerts its effects by antagonizing the estrogen receptor in some tissues, and agonizing it in others. In this way, certain estrogenic pathways are activated and others are blockaded. It seems to exert estrogenic effects on blood lipids, reducing LDL and total cholesterol, as well as estrogenic effects on bone, improving density.
It would also appear to exert anti-estrogenic effects in breast tissue, displacing the traditional effects of estrogen, effectively helping prevent breast cancer in postmenopausal women. Evista only raises Testosterone by about 20%, much less than Nolva. Common Evista doses are 30-150 mgs. It is better utilized during a cycle versus being used in PCT.
Toremifene: Usually dosed around 60 mgs, some dose it up to 240 mgs. Its androgenicity:estrogenicity ratio is 5x that of Nolvadex. It is prescribed to female patients for breast cancer and has shown a high affinity for bonding to the Estrogen receptors in the breast tissue. Male patients treated with toremifene citrate 80 mg compared to placebo demonstrated statistically significant increases in bone mineral density in the lumbar spine, hip, and femur skeletal sites. It decreased the risk by up to 50%. Toremifene citrate 80 mg treatment compared to placebo also resulted in a decrease in total cholesterol, LDL, and triglycerides, and an increase in HDL. There were also statistically significant improvements in gynecomastia. This data are from an ongoing study of men receiving treatment for ADT (androgen depravation therapy). These men are receiving ADT for advanced prostate cancer. ADT removes much of the testosterone and estrogen in the body which helps the prostatic cancer cells grow. So these men were suffering from side effects from reduced estrogen and testosterone in the body. Some studies have even suggested that Torm doesn't regulate progesterone receptors and we may see in the future the possibility of using it with 19-nors.
Some possible side effects include the risk of stroke, pulmonary embolism, and cataracts.
A typical PCT of Toremifene only would be similar to this:
Week 1: 120mg ED
Week 2: 90mg ED
Week 3: 60mg ED
Week 4: 30mg ED
Arimidex: A-dex, seems to be the aromatase inhibitor of choice. Usually doesed from 0.25 - 3.0 mg it is effective even when not used every day. 0.5mgs per day can get rid of up to 50% estrogen.
Aromasin: Aromasin is usally doesed from 20-50 mgs per day. It can raise blood testosterone by 60%, and also help out your free to bound testosterone ratio by lowering levels of Sex Hormone Binding Globulin (SHBG), by about 20%! It can suppress estrogen by 65-80%. It's a third generation Aromatase Inhibitor just like A-dex and Letro, but unlike these A-dex and Letro, it is a Type I inhibitor. Whats the difference in a Type I and II inhibitor? Well, Type I inhibitors (like Aromasin) are actually steroidal compounds, while type II inhibitors (like Letro and A-dex) are non-steroidal drugs.
Hence, androgenic side effects are very possible with Type-I AIs, and they should probably be avoided by women. Of course, there are some similarities between the two types of AIsï¿½?ï¿½both type I & type II AIs mimic normal substrates (essentially androgens), allowing them to compete with the substrate for access to the binding site on the aromatase enzyme. After this binding, the next step is where things differ greatly for the two different types of AI's.
In the case of a type-I AI, the noncompetitive inhibitor will bind, and the enzyme initiates a sequence of hydroxylation; this hydroxylation produces an unbreakable covalent bond between the inhibitor and the enzyme protein. Now, enzyme activity is permanently blocked; even if all unattached inhibitor is removed. Aromatase enzyme activity can only be restored by new enzyme synthesis.
Now, on the other hand, competitive inhibitors, called type II AI's, reversibly bind to the active enzyme site, and one of two things can happen: 1.) either no enzyme activity is triggered or 2.) the enzyme is somehow triggered without effect. The type II inhibitor can now actually disassociate from the binding site, eventually allowing renewed competition between the inhibitor and the substrate for binding to the site. This means that the effectiveness of competitive aromatase inhibitors depends on the relative concentrations and affinities of both the inhibitor and the substrate, while this is not so for noncompetitive inhibitors.
Aromasin is a type-I inhibitor, meaning that once it has done its job, and deactivated the aromatase enzyme, we donï¿½??t need it anymore. Letrozole and Arimidex actually need to remain present to continue their effects. This is possibly why Nolvadex does not alter the pharmacokinetics of Aromasin.
Letro: Letrozole is currently the most powerful aromatase inhibitor available. It has been shown to reduce estrogen levels by 98% or more. Intravenous administration of Letrozole lowered Estrogen by 46% in the young men tested, and 62% in the elderly subjects. Because estrogen is part of the negative feedback loop of the HPTA, Letrozole (and other anti-estrogens) are able to raise testosterone in male subjects. Letrozole was studied in men, and found to significantly increase LH levels to a 339 and 323% in the young and the elderly, respectively and Testosterone by 146 and 99%, respectively.
Letrozole was also able to produce a peak LH response to Gonadatropin Releasing Hormone equal to a 152 and 52% increase from baseline in either young or older men, respectively. In a similar study 0.02 mg of Letrozole increased testosterone by 45% after 2 days. That same twenty micrograms of Letrozole was also enough, in one study done on men, to reduce estrogen levels by roughly a third. Letrozole has a 2-4 day half-life, and it needs to be taken for up to 60 days to get a steady blood plasma level. Letro is best dosed from 0.125-2.5 mgs depending on the desired effect.