Is there a need to control estrogen while on TRT?

This is a short article on reasons why men do NOT need to block estradiol while on TRT.

Quick answer, NO!

First off, what is estradiol?

Estradiol (E2), is a sex hormone produced in males and females. We know it is very important in female physiology but consider also that it is extremely important in male physiology too. Although estradiol affects tissues throughout the body, from the brain, organs, bones, the priority tissue I am thinking about is the vascular system. Estradiol plays a dominant role in the production of Nitric Oxide (NO) molecule in the endothelium. This is the inner most layer of blood vessels that is a single cell layer thick. Nitric Oxide release within the endothelium promotes vasodilation/relaxation and improved blood flow. This leads to improved cardiovascular health. Neat!

The fear of too high estradiol levels lead many men to seeking a way to block its production. The most popular way to do this is by using a class of medication known as aromatase inhibitors to prevent the convertion of testosterone to estradiol. The use of this medication can lead to consequences in all organ systems including the vascular endothelium.

What is aromatase and what is an aromatase inhibitor?

Aromatase is an enzyme found within the cell. The function of aromatase is to convert testosterone into estradiol within the cell. An aromatase inhibitor does exactly as the name implies, it blocks aromatase.

Why should we not use aromatase inhibitors?

The studies utilizing aromatase inhibitors (AIs) in men with testosterone deficiency is limited and of poor quality. There is not any randomized controlled trial that shows benefits to men on TRT when they blocked estradiol (estrogen.) In all of the studies where testosterone was used in men and showed beneficial effects none of these studies utilized an aromatase inhibitor to block estradiol.

The practice of using aromatase inhibitors, such as anastrozole, comes from the bodybuilding world. Bodybuilders want to add as much lean mass as possible. So they use AIs to block estradiol to have more free testosterone available to grow muscle tissue, but this comes at the expense of decreasing overall health.

Testosterone has its beneficial effects in many tissues via its conversion into its active metabolites, DHT and Estradiol. When a man produces his own testosterone or utilizes testosterone therapy, testosterone travels down three pathways. One, the direct pathway where testosterone will act directly on cells such as in skeletal muscle. Two, the amplification pathway where testosterone is converted, via 5 alpha reductase, into DHT such as in the skin and prostate. And third, the diversification pathway where testosterone is converted, via aromatase, into estradiol such as in the brain, bone, blood vessels, heart, and the liver. When we block testosterones conversion into estradiol then we block testosterones beneficial effects at the target tissues were testosterone acts through its active metabolite estradiol.

Take away: When testosterone therapy is provided correctly there is no need to use an aromatase inhibitor. Estradiol is vitally important in many physiologic functions across the body. This inlcudes cardiovascular health, bone density, spermatogenesis, cognition, mood, and sexual function. For these reasons, we do NOT recommend the use of aromatase inhibitors in majority of cases. If the goal is optimal health and longevity, estradiol needs to be apart of the plan as it is such an important contributor to overall health.