Estrogen Blockers for Men: Everything You Need to Know

The terms “male” and "men" are used in this article to refer to people who identify as male and have typical reproductive organs of a cisgender male. We recognize that some people who identify as male do not have the same anatomy as depicted in this article.

Testosterone and estrogen are hormones produced by the endocrine system in the body. The levels of these hormones can change over time as people age.

An excess or imbalance of hormones can cause health problems for men. Among the treatment options for those with low testosterone are medications that block the activity or production of estrogen.

Read on to learn more about the function of hormones, symptoms of a testosterone or estrogen imbalance, treatments that block estrogen, and when to see a healthcare provider.

Healthcare provider using a tablet and talking with older patient

Ariel Skelley / Getty Images

What Are Hormones?

Hormones are chemical messengers in the body. They are produced by the glands in the body's endocrine system, which includes the:

Hormones are released by these glands and then travel through the bloodstream. They impact many functions in the body, from growth and development, mood, sexual reproduction, and metabolism.

The endocrine system also regulates the levels of hormones in the body. However, an imbalance of too little or too much of a given hormone in the body can be harmful. A change in the amount of certain types of hormones in the body can be impacted by:

  • Stress
  • Age
  • Having an infection
  • Imbalance of fluids or minerals in the body (such as being dehydrated)

A change in the level of hormones a person has can contribute to changes in levels of other hormones in the body.

Testosterone levels decrease as people age, which can be due to abnormalities of the hypothalamic-pituitary-testicular axis (which controls essential hormones) or obesity. When testosterone levels decrease, aromatase activity may increase. Aromatase is an enzyme that converts androgens (testosterone is a type of androgen) to estradiol, a type of estrogen.

This increased activity can create an excess of estrogen and an imbalance between the two hormones. The imbalance is associated with a number of health issues for men.

Age-Related Testosterone Decrease

Testosterone typically decreases in the body as men get older, referred to as late-onset hypogonadism. Though the exact prevalence is not certain, researchers believe up to 25% of men may experience a decrease in testosterone as they age.

Estrogen in Men

Estrogen is often thought of as a female hormone, as the ovaries produce much of the hormone. However, men also have estrogen in their bodies. About 20% of the male body's estrogen is produced by the testes. The rest is produced in body fat, the brain, skin, and bones.

Estrogen in the male body impacts many functions. Among those functions, it supports:

  • Maintenance and growth of bones
  • Coordination of head and eye movement to support vision
  • The type and location of fat in the body and metabolism
  • Sexual functioning in relation to libido (sexual drive), erectile functioning, and the creation of sperm

Symptoms of Estrogen and Testosterone Imbalance

Changes to the ratio of estrogen and testosterone in the body can result in health problems for some people. For example, in people with late-onset hypogonadism, lower testosterone levels and an increase of androgens being converted to estradiol is associated with a number of health issues, including:

  • Infertility
  • Reduced sex drive
  • Reduced muscle mass and energy
  • Erectile dysfunction
  • Hot flashes
  • Decreased testicle size
  • Gynocomastia (enlarged breast growth)
  • Low-energy fractures (where bone fractures occur due to falling from a standing height or less)

Aromatase excess syndrome is a rare genetic condition that results in higher levels of estrogen. It can affect some young men and lead to late childhood developmental symptoms. In addition to breast growth, the associated symptoms include:

  • Quicker than normal physical development that stops sooner than others
  • Short stature

Estrogen Blockers

Estrogen blockers are a type of treatment that reduces the amount or functioning of estrogen in the body.

Several estrogen blocker medications used to treat the imbalance of testosterone to estrogen were initially developed for use in treating breast cancer in women. However, they have been prescribed for off-label use in male patients.

Off-Label Use of Medications

Prescribing drugs "off-label" means that a healthcare provider has prescribed a medication that is approved by the Food and Drug Administration (FDA) but that is not approved for the condition or purpose it is being prescribed. A provider may prescribe an approved drug to treat a condition or purpose that the drug was not approved for at their own professional discretion.

Medications

Medications used as estrogen blockers include:

  • Aromatase inhibitors (AI): This medication can increase testosterone, along with other hormones, by inhibiting the ability of androgens to be converted to estradiol in the body. This decreases the overall level of estrogen in the body. The medication also acts on the hypothalamus and pituitary gland to increase luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the body, which may support healthy sperm. Some available AI medications used for this purpose are anastrazole and letrozole.
  • Selective estrogen receptor modulators (SERM): These medications bind to estrogen receptors to prevent estrogens from binding with each other. A similar function of releasing LH and FSH can also be achieved by use of SERM. Common SERM medications used to address the hormonal balance in men include tamoxifin and clomiphene citrate.

Side Effects

Estrogen-blocking medications have been prescribed for off-label use in those with low testosterone for some time and are often well-tolerated. However, there aren't established guidelines for their use in men. More long-term studies are needed to establish efficacy and safety of the medications for this specific purpose.

That said, some research has found these reported side effects:

  • AI: In general, AI are well-tolerated by those who use them for this purpose. Side effects may include nausea, increase in liver enzymes, headaches, and hot flashes.
  • SERM: Researchers have noted that clomiphene citrate has minimal side effects while being able to increase testosterone levels and improve bone mineral density and androgen deficiency. Rare side effects for clomiphene citrate include headaches, changes in vision, and gynecomastia (enlargement of male breasts). Use of tamoxifen may involve more significant side effects, including gastrointestinal upset, risk of blood clots, and cardiovascular problems.

When to Talk to Your Provider

If you are experiencing any symptoms associated with an imbalance of testosterone and estrogen, particularly reduced sexual desire and erectile dysfunction, speak with a healthcare provider to help you determine the exact cause. To investigate whether hormones may be at the root of your symptoms, they may do a blood test to measure your hormone levels.

If your hormone levels meet the criteria for a diagnosis such as hypogonadism, they can also advise on treatment options. These can range from changing lifestyle factors (such as sleep and diet) to medications.

Summary

Testosterone and estrogen are hormones that play key roles in the male body. There are a number of symptoms and health conditions that are associated with an imbalance between these hormones, such as sexual dysfunction, reduced energy, and enlarged breasts.

If you experience any of these symptoms, speak with a healthcare provider to help you determine a cause. If too little testosterone or too much estrogen is at the root of these types of symptoms, estrogen blockers may be prescribed for off-label use as treatment. Most estrogen blockers are well-tolerated, but there are some side effects.

A Word From Verywell

As men get older, reduced testosterone is common. Symptoms of this imbalance can be sensitive in nature for some, such as sexual dysfunction or breast enlargement. Speaking with a healthcare provider about any changes you observe can help them investigate the root cause of your symptoms. If hormone levels are contributing, you can discuss the benefits and risks of treatment options that can help improve your symptoms and quality of life.

Frequently Asked Questions

  • Is it safe to take estrogen blockers and testosterone at the same time?

    Some research supports the safe and effective use of estrogen blockers and testosterone therapy at the same time. Both may be used because testosterone therapy can increase the amount of estrogen in the body due to an increase in aromatase activity.

    Aromatase is an enzyme that converts testosterone to estradiol, a type of estrogen. One study found that taking an estrogen blocker called an aromatase inhibitor while on testosterone therapy reduced estrogen and addressed low testosterone levels.

  • At what age do men start to lose testosterone?

    In general, men begin to lose testosterone at a rate of 1%-2% each year after they turn 40. One study found that 20% of men over the age of 60 and 50% of those over the age of 80 experience lower levels of testosterone. However, not all people who experience age-related reductions in testosterone will have symptoms due to the change in testosterone levels.

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17 Sources
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  1. MedlinePlus. Hormones.

  2. Bhasin S, Valderrábano RJ, Gagliano-Jucá T. Age-related changes in the male reproductive system. In: Feingold KR, Anawalt B, Boyce A, et al., eds. Endotext. MDText.com, Inc.; 2000.

  3. Mintziori G, Nigdelis MP, Mathew H, Mousiolis A, Goulis DG, Mantzoros CS. The effect of excess body fat on female and male reproductionMetabolism. 2020;107:154193. doi:10.1016/j.metabol.2020.154193

  4. Dudek P, Kozakowski J, Zgliczyński W. Late-onset hypogonadismPrz Menopauzalny. 2017;16(2):66-69. doi:10.5114/pm.2017.68595

  5. Chan HJ, Petrossian K, Chen S. Structural and functional characterization of aromatase, estrogen receptor, and their genes in endocrine-responsive and –resistant breast cancer cellsJ Steroid Biochem Mol Biol. 2016;161:73-83. doi:10.1016/j.jsbmb.2015.07.018

  6. de Ronde W, de Jong FH. Aromatase inhibitors in men: effects and therapeutic optionsReprod Biol Endocrinol. 2011;9:93. doi:10.1186/1477-7827-9-93

  7. Surampudi PN, Wang C, Swerdloff R. Hypogonadism in the aging male diagnosis, potential benefits, and risks of testosterone replacement therapyInt J Endocrinol. 2012;2012:625434. doi:10.1155/2012/625434

  8. Cooke PS, Nanjappa MK, Ko C, Prins GS, Hess RA. Estrogens in male physiologyPhysiological Reviews. 2017;97(3):995-1043. doi:10.1152/physrev.00018.2016

  9. Hammes SR, Levin ER. Impact of estrogens in males and androgens in femalesJ Clin Invest. 2019;129(5):1818-1826. doi:10.1172/JCI125755

  10. Schulster M, Bernie AM, Ramasamy R. The role of estradiol in male reproductive functionAsian J Androl. 2016;18(3):435-440. doi:10.4103/1008-682X.173932

  11. MedlinePlus. Aromatase excess syndrome.

  12. Awouters M, Vanderschueren D, Antonio L. Aromatase inhibitors and selective estrogen receptor modulators: Unconventional therapies for functional hypogonadism? Andrology. 2020;8(6):1590-1597. doi:10.1111/andr.12725

  13. United States Food and Drug Administration. Understanding unapproved use of approved drugs "off label".

  14. Rambhatla A, Mills JN, Rajfer J. The role of estrogen modulators in male hypogonadism and infertilityRev Urol. 2016;18(2):66-72. doi:10.3909/riu0711

  15. Krzastek SC, Smith RP. Non-testosterone management of male hypogonadism: an examination of the existing literatureTransl Androl Urol. 2020;9(Suppl 2):S160-S170. doi:10.21037/tau.2019.11.16

  16. Huhtaniemi I. Late-onset hypogonadism: Current concepts and controversies of pathogenesis, diagnosis and treatmentAsian J Androl. 2014;16(2):192-202. doi:10.4103/1008-682X.122336

  17. Punjani N, Bernie H, Salter C, Flores J, Benfante N, Mulhall JP. The utilization and impact of aromatase inhibitor therapy in men with elevated estradiol levels on testosterone therapySex Med. 2021;9(4):100378. doi:10.1016/j.esxm.2021.100378