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April 27, 2015

Aromatase Inhibitors in Men to Prevent Man Boobs

Why Do Men Use Estrogen Blockers?

Aromatase inhibitors are drugs or supplements that block the conversion of testosterone into estrogens. The best known prescription aromatase inhibitor is anastrozole (Arimidex is the brand name). Anastrozole is most frequently used in the treatment of breast and ovarian cancer in postmenopausal women. These drugs are frequently called estrogen blockers. Specifically aromatase inhibitors block the enzyme aromatase that converts testosterone into estrogens and that makes effective in preventing those dreaded man boobs. So why would a man use an aromatase inhibitor? There are two main situations in which an aromatase inhibitor might be prescribed or recommended in men. The most common reason is to prevent excessive conversion of testosterone into estrogen in men receiving testosterone replacement therapy. 

aromatase inhibitors

Estrogen is a proliferative hormone meaning it causes tissue growth and specifically growth of breast tissue. While we might think that is desirable in women, it is not so desirable in men. Yes, high estrogen in men leads to the infamous man boobs. But it can also cause breast and nipple tenderness.

The second place where aromatase inhibitors are used are in men who naturally have too little testosteronewhile making too much estrogen. This is most common in obese men as the aromastase enzyme that converts testosterone into estrogen is found in high concentrations in fat or adipose tissue. Overweight men many times have man boobs. Now you know why.

In these obese men too much testosterone is converted into estrogen leading to a decline in free testosterone and the development low T or testosterone deficiency. In these men blocking estrogen is sometimes enough to raise their testosterone to adequate levels.

For either situation generally a small dose of anastrozole is all that is needed to bring estradiol (the main estrogen) into a safe range which is considered 20-40 pg/ml. A typical dose for men is 0.5 mg twice a week. For comparison the typical dose for treating women with breast or ovarian cancer is 1 mg daily.

In most men testosterone replacement can be managed in a way that excessive estradiol levels can be prevented without the need for estrogen blockers. Losing weight goes a long way in controlling estrogen levels in men on testosterone therapy. However, if needed there are plenty of options to lower estrogen.

Aromatase Inhibitors

In addition to anastrozole there are several other aromatase inhibitors.

  • Letrozole (Femara)
  • Exemestane (Aromasin)
  • Vorozole (Rivizor)
  • Formestane (Lentaron)
  • Fadrozole (Afema)
  • Aminoglutethimide
  • Testolactone (Teslac)

Some aromatase inhibitors block aromatase permanently and others temporarily. Anastrozole is a reversible (temporary) inhibitor. The permanent inhibitors are used more often in the treatment of cancers.

Over the Counter Estrogen Blockers

Over the counter estrogen blockers are available as well in the form of nutritional supplements. They are not as effective as prescription drugs but can work well in some men and worth trying before a prescription aromatase inhibitor.

Over the counter estrogen blockers include:

  • zinc
  • chrysin
  • quercetin
Aromatase Inhibitors in Men to Prevent Man Boobs

The dose for zinc is 60 to 100 mg a day. Chrysin is used frequently by bodybuilders. It’s not well absorbed though and should be taken with piperine (black pepper extract) to enhance absorption. The dose for chrysin is 750-1500 mg a day along with 7.5 to 15 mg of piperine. Quercetin is found in red wine. The dose of quercetin is 1,000 to 2,000 mg a day.

So for men being treated with testosterone therapy there are many available options to keep estrogen in a safe range and prevent those dreaded man boobs.

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Dr. Joe Jacko


Dr. Joe is board certified in internal medicine and sports medicine with additional training in hormone replacement therapy and regenerative medicine. He has trained or practiced at leading institutions including the Hughston Clinic, Cooper Clinic, Steadman-Hawkins Clinic of the Carolinas, and Cenegenics. He currently practices in Columbus, Ohio. Read more about Dr. Joe Jacko

  1. You mentioned three supplements zinc, chrysin and quercetin along with their recommended dosages but do you recommend all three together? Or any two, or just one. I also suffer from low T and a urologist prescribed “chlomephine citrate” before testosterone treatment. This brought my level from 150 up to 230, but never any higher even with increased dosage. I haven’t taken the plunge into T therapy because I have heard of a few side effects I don’t like and I just haven’t taken the time to research it. I am a 57 yr old male 6’ tall and currently 230#, down from 245#. I stay between 225-235# just naturally. I know I need to exercise. Two years ago I got down to 208# through diet and walking. I felt great but still dealt with “man boobs”. I have had them as far back into my childhood as I can remember. Also, what is your opinion on soy based protein products contributing to man boobs? Thank you for the article and your reply.

    1. Recommend starting with zinc and chrysin together. If you have man boobs then your estrogen level (estradiol) is probably too high. Testosterone gets converted into estradiol in our fat stores. So losing weight would help lower the estradiol level. Also, taking an estrogen blocker like anastrozole (prescription drug) will help prevent the conversion of testosterone to estradiol – thus raising testosterone and lowering estradiol. So you may want to consider that as an option. For clomiphene to work you have enough Leydig cells in the testes that are still working. By the time you are in your mid 50s most men do not have enough Leydig cells for clomiphene to work well enough. If estrogen is high would recommend staying away from soy products as they tend to raise estrogen.

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