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. 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 testosterone while 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.
In addition to anastrozole there are several other aromatase inhibitors.
- Letrozole (Femara)
- Exemestane (Aromasin)
- Vorozole (Rivizor)
- Formestane (Lentaron)
- Fadrozole (Afema)
- 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:
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.