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Man Seeks Cause For Big Breasts (“Man Boobs”) aka Gynecomastia

A surprising number of medications can cause breast enlargement in men. It is also known as gynecomastia and can be quite embarrassing.

It’s not the sort of side effect physicians are likely to talk about. That’s because male patients may not be thrilled to learn that a medicine they are about to take could cause what some men refer to as man boobs. The medical name for this condition is gynecomastia. Like so many medical terms, this comes from the Greek gyneco (feminine or female) and mastos (breast). It literally means enlarged male breasts.

Men Make Estrogen!

Most men think that the only hormone that matters to them is big T (testosterone aka androgen). That is not true. Men also make estrogen hormones. In fact, males produce about twice as much estrogen as women who have gone through menopause.

Where does estrogen come from? The answer may surprise you. Testosterone is the precursor for estrogen production in both men and women.

Hot flashes occur in both men and women when estrogen production is reduced. That may be why men undergoing treatment for prostate cancer with anti-androgen drugs (also known as ADT or androgen deprivation therapy) may experience similar hot flashes to the ones women complain about during menopause. Some prostate cancer oncologists actually prescribe estrogen to men to ease their night sweats and flushes while undergoing ADT.

What Causes Gynecomastia?

So, what causes gynecomastia in men? Remember, men make estrogen. If there is enough of a change in testosterone levels that the delicate balance between estrogen and testosterone is altered, the remaining estrogen can stimulate breast tissue growth.

Another hormone that does this is prolactin. It plays a crucial role in mammary gland formation and breast milk production in pregnant women. Men also make prolactin. When levels of this hormone increase, they too may trigger male breast enlargement.

By the way, obesity can also cause gynecomastia. That’s because people who are overweight make more estrogen, which in turn can stimulate breast enlargement.

There is another contributor to breast growth in men. Medications. We suspect that this is an often-neglected adverse reaction. It can take months to develop. Consequently, drug companies that perform relatively short clinical trials to get FDA approval may not 1) ask questions about breast enlargement or 2) wait long enough to learn if it is a drug-induced complication.

Drugs That Can Contribute to Gynecomastia:

This reader asks if his medications could have contributed to his breast enlargement:

Q. My wife thinks I have gynecomastia. I may; I do have man boobs, but it could be from being overweight.

If I do have gynecomastia, I guess it could be from some of the medications I take and/or the weight. I realize the only way to be positive is a doctor’s exam. I have one scheduled in about two months. Is there anything I can do to test myself and get an idea if I might or might not have gynecomastia?

A. Gynecomastia is the medical term for enlarged male breasts. Some adolescents develop this condition temporarily, but they usually outgrow it within a few years.

Weight can be a contributing factor. So can many medications. Some examples include cimetidine (Tagamet), eszopiclone (Lunesta), leuprolide (Lupron), spironolactone (Aldactone) and finasteride (Proscar).

This condition requires medical diagnosis. Although there is no test you can do yourself for gynecomastia, your doctor will check your hormone levels and rule out various tumors. If a medication is responsible, it may be possible for your doctor to prescribe an alternative less likely to trigger breast enlargement.

Can Heart Pills Cause Gynecomastia?

This reader is taking a medication to control his heart arrhythmias:

Q. I was recently diagnosed with gynecomastia. Could that be a side effect of taking amiodarone for heart rhythm problems?

I know that amiodarone has many serious side effects, but neither my cardiologist nor my endocrinologist know of any definitive connection between that drug and gynecomastia.

A. Gynecomastia, the development of large breasts on men, may be a side effect of hormone imbalance or medications.

We searched high and low for a link between the heart rhythm drug amiodarone and gynecomastia. There is nothing in the prescribing information, but doctors in Israel reported a case decades ago (New England Journal of Medicine, Dec. 11, 1986). Because the patient’s breasts diminished in size when the drug was discontinued and reappeared when it was restarted, the physicians concluded that the breast enlargement was the result of the medication. No one should ever stop amiodarone without medical approval and supervision!

Other Medications That Can Trigger Gynecomastia:

Hundreds of drugs can cause breast growth, but it is not a side effect that gets much attention. Prostate cancer medications and certain drugs prescribed for high blood pressure, heartburn, fungal infections and mental illness can also trigger breast enlargement in men.

An Imperfect List of Drugs That May Cause Gynecomastia

As described above, it is hard to know how likely a medication is to cause breast enlargement in men. Clinical trials are not designed to detect the gradual onset of this adverse reaction. The following list is imperfect, but we offer it as a starting place to discuss this kind of adverse reaction with the prescribing physician.

  • Abiraterone (Zytiga)
  • Amitriptyline (Elavil)
  • Amlodipine (Norvasc)
  • Aripiprazole (Abilify)
  • Bicalutamide (Casodex)
  • Chlorpromazine (Thorazine)
  • Cimetidine (Tagamet)
  • Diazepam (Valium)
  • Digoxin (Lanoxin)
  • Diltiazem (Cardizem)
  • Dutasteride (Avodart)
  • Felodipine (Plendil)
  • Finasteride (Proscar)
  • Fluphenazine (Prolixin)
  • Flutamide (Eulexin)
  • Haloperidol (Haldol)
  • Imipramine (Tofranil)
  • Indinavir (Crixivan)
  • Ketoconazole (Nizoral)
  • Lopinavir/Ritonavir (Kaletra)
  • Methadone (Dolophine)
  • Methotrexate (Trexall)
  • Methyldopa (Aldomet)
  • Metoclopramide (Reglan)
  • Nelfinavir (Viracept)
  • Nifedipine (Procardia)
  • Olanzepine (Zyprexa)
  • Omeprazole (Prilosec)
  • Perphenazine (Trilafon)
  • Phenytoin (Dilantin)
  • Prednisone
  • Quetiapine (Seroquel)
  • Risperidone (Risperdal)
  • Rosuvastatin (Crestor)
  • Spironolactone (Aldactone)
  • Thioridazine (Mellaril)
  • Trifluoperazine (Stelazine)
  • Verapamil (Calan, Verelan)
  • Zidovudine (Retrovir)
  • Ziprasidone (Geodon)

What To Do About Drug-Induced Gynecomastia?

Some medications cannot be discontinued. Men who must take abiraterone to combat prostate cancer cannot stop their medicine without a green light from the prescribing physician. That also holds true for antiviral drugs used to treat HIV/AIDS. No one should ever stop a medication without careful consultation with the prescriber.

In some cases, a change in blood pressure medication or a different drug to treat heartburn could help control gynecomastia. This list is incomplete, but it is a starting place for a conversation with a health care professional.

Can cholesterol-lowering statin-type drugs contribute to gynecomastia? We had to do quite a bit of digging to uncover a connection. You can read about it at this link.

Please share your own story about breast enlargement in the comment section below.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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