T Nation

Adjusting Anastrozole Dose for Increased Testosterone Dosage


I have searched this forum and others, read a few clinical studies, and cant seem to find a good answer on exactly how anastrozole works.

Assume someone has nailed down their anastrozole dosing to get their estradiol into the “sweet spot” around 22 pg/mL with their current testosterone regime. Now that individual wants to increase their testosterone dosage to raise total T. Will that individual need to increase their anastrozole dosage to stay in the ideal range? If so, will the dosage increase of anastrozole correlate with the testosterone increase, ie. a 20% increase in testosterone cypionate should require a 20% increase in anastrozole?

I ask because on my initial post KSman recommended 1 mg per every 100 mg Test Cyp. Another member, Nashtide, explained that anastrozole attaches to aromatase and as you have a fixed amount of aromatase in your body, increased testosterone shouldn’t effect the impact anastrozole has on estradiol. I cannot find anything correlating an increase in testosterone with an increase in aromatase production, so Nashtides assessment makes sense.

So to summarize my questions, is anastrozole dosing connected to testosterone dosing or is it dependent on ones fixed aromatase levels? Does an increase in total testosterone allow the unbound aromatase to create more estrogen then it would at a lower testosterone level (more gas pumped into the same sized burner)? If increased testosterone dosages does require additional anastrozole, is there a general rule of thumb for titrating the anastrozole to accommodate the increased testosterone?


You are asking a question that doesn’t have a simple answer. First, the amount of aromatase enzymes that someone has can be very varied. Things like genetics, body fat, age, etc are all factors. So a healthy, athletic 21 year old with 12% body fat is going to require a lot less AI to control the same amount of T as. 50 year old, overweight couch potato. Second, you will need more AI if you increase T dose UP TO A POINT. As I’ve mentioned before, bb guys taking 1000mg of T don’t take 10mg of Adex! Not even close. So the bottom line is if you increase T the only way to know for sure if you need to increase AI is to run labs about four weeks after the change


Thanks Nashtide. Do we know why we need more anastrozole with increased T? I would guess that it means the unbound aromatase is able to produce more estrogen do to the increase in raw materials.


Anastrozole is a competitive drug. Competitive with T at aromatase reaction sites. That alone suggested to me that the relationship would be linear at therapeutic dosing. My experience and that of may others shows that that assumption works very well. It works to adjust anastrozole to correct to target and to correct to T dose change and has been shown to work with both change calculations at once. The clinical experience is hear, not in medical publications.


Enzymatic reactions are instantaneous. For our purposes, there are basically two types of chemicals classifications when it comes to affecting enzymes. There are those chemicals which attach to the enzyme site and permanently disable the enzyme. Many poisons work this way. Then there are chemicals which are attach to the enzyme, stay for a period of time then detach and leave the enzyme in perfect condition. This is how Adex works. So while the Adex is attached to the aromatase enzyme, ,T cannot attach and is therefore not converted to E2. When someone is on TRT, we have three factors, exogenous T, an AI and aromatase enzymes. So how can we lower T->E2? Either decrease T, increase AI or reduce the amount of aromatase enzymes.

Because the human body is so complex, the relationship between T and an AI is linear up to a point. The nice thing for us old guys on TRT, because of our T doses, it’s mostly linear.


Thank you for the detailed explanation.