So we see we have 2 categories of compounds that can be of use to us in properly managing Estrogen or its side effects, Serms and AIs. Let''s take a look at our options in categories, their differences and potential interactions with one another, and how they might be used together to accomplish our goal.
First we will look at AIs as in my opinion they are the core of our Estrogen Management program. [We essentially have 2 types of AI''s to choose from. Type 1 AIs like Exemestane and Type 2 AI''s such as letrozole or Anastrozole (arimidex). The difference in these types is as follows. A Type 1 Aromatase inhibitor (AI) like Exemestane binds permanently to the site on the Aromatase Enzyme where it binds to testosterone allowing its conversion to Estrogen. This permanent binding renders the Aromatase totally and permanently inactive. In contrast Type 2 AIs temporarily bind to this site on the Aromatase Enzyme rendering it inactive as long as the Aromatase inhibitor (AI) is being used. Onçe use of type 2 Aromatase inhibitor (AI) stops the aromatase will reactivate. So whats the difference in these Aromatase inhibitor (AI) types for our purposes? Well Due to the '"reactivation" if you will of existing Aromatase with a Type 2 Aromatase inhibitor (AI), when you stop using it a spike in Estrogen (often referred to as rebound) will occur due to the sudden increase availability of Aromatase Enzyme. Another important distinction when it comes to Type 1 and Type 2 AI''s. A Type 1 Aromatase inhibitor (AI) like Exemestane remains unaffected by the introduction of a serm into your Estrogen management program. Type 2 AIs like letrozole and Arimidex suffer a reduced in blood levels and effectiveness with the introduction of some serms. I will touch more on why we may need to introduce a serm a little farther on in this article.
When it comes to the strength of these AI''s letrozole would be the strongest followed by Arimidex and then by Exemestane. Now people might be up in arms saying Exemestane is stronger than Arimidex however when one looks and compare data from studies done on MALES the order of strength is exactly as I stated it, quite often much confusion comes in to play when people recite data on AI's taken from studies on women. The fact is AI's behave differently in males, they are less effective in males, and for our purposes it is only prudent to compare data gathered from studies on males to portray an accurate picture.
The next aspect to be considered when looking at AIs are the effects they indirectly illicit in other areas. We stated the positive effects of Estrogen, we must realize by lowering Estrogen via Aromatase inhibitor (AI) use some of these positive effects may be compromised. It is important to look at the various Aromatase inhibitor (AI) options available and possibly use the data to help pick which Aromatase inhibitor (AI) we use. letrozole is an extremely potent Aromatase inhibitor (AI) and its effects demonstrate this as would be expected. letrozole has an adverse effect on lipid profile and somewhat on IGF levels. On the other hand Arimdex has a small impact in the area of IGF and depending upon which studies you cite a small adverse impact on lipids to no adverse impact on lipids. Exemestane seems to have no clinical impact on either IGF or lipids.
It is important to realize that it may seem like Exemestane shines as a clear cut winner when it comes to choice of Aromatase inhibitor (AI), however I do not necessarily believe this to be the case for everyone. In some cases or maybe better said in some people, an extremely powerful Aromatase inhibitor (AI) like letrozole must be used to manage Estrogen properly. Some may respond better to Arimidex than Exemestane. I believe there is a place for all 3 of these. That being said, if possible my personal first choice of Aromatase inhibitor (AI) is Exemestane due to its lack of interaction with other compounds we may need to introduce such as certain serms, its positive effects on IGF and Lipids over other options, and also its lack of potential "rebound"(although I think that is an overstated issue quite often)
