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Causes Of Gynecomastia: Why Men Grow Breasts Like Women

Causes of gynecomastia include genetic factors, medication side effects, unsystematic steroid use and a diet rich in estrogen.

Causes Of Gynecomastia: Why Men Grow Breasts Like Women2019-03-04T06:19:21-05:00

The causes of gynecomastia have always been somewhat of a mystery. Since it is a benign condition, not much effort was put into finding what causes gynecomastia at a root level. But before delving deep into the causes of gynecomastia, let’s be clear and on the same page about what is gynecomastia and what it is not. Breast enlargement in adult men caused by excessive breast tissue growth is genuine gynecomastia [1]. Breast enlargement in men can also be caused by fat being built up behind and around the areola and this is called pseudogynecomastia or adipomastia or lipomastia [2, 3].

Anatomy Of Gynecomastia

An illustration showing breast tissue growth as one of the causes of gynecomastia.

Breast Tissue Growth In Teenagers

approximately 48-64% of teenagers develop some excess breast tissue in their adolescence

You did not come here to read that excess breast tissue growth among adolescents is normal, right ?. That is the truth and let me tell you why + a really good news. Breast tissue growth happens in men during three stages in the life span of an individual and they are infancy, adolescence and old age [4]. When teenagers go through puberty and becomes sexually mature, there are a lot of hormonal changes including estrogen dominance for some time and this can cause the development of breast tissue [5]. Not all boys going through puberty will experience this but it is estimated that between 50-64% of all adolescents will have some form of breast tissue growth [4]. This is called pubertal or teenage gynecomastia [6].

Gynecomastia In Teenagers

Now the good news is that this is quite natural and this excess breast tissue will flatten out as you enter adulthood and there will not be any abnormality for your chest in appearance or when touched. So if you are thinking about that little breast tissue you have now as a teen is an exception, know that 6 out of 10 of your peers will have the same. There is one very crucial advice that you need to take to heart if this should go away naturally. In normal circumstances, you do not need any treatment. Avoid marijuana and drugs like the plague [7], be active, do not put a lot of weight and you should be fine by the time you enter adulthood.

Causes Of Gynecomastia In Adults

Almost all causes of gynecomastia can be in one way or other traced back to excess production of the female hormone estrogen [8]. This excessive level of the female hormone estrogen signals the body to develop breast tissue and that is how gynecomastia is caused. This is the most basic explanation. How this excess estrogen is caused a little more complex and we will take a look at the factors that come into play.

the negative feedback loop that causes gynecomastia

It all starts with an excess of the female hormone estrogen in the male body due to a wide variety of reasons. It can be excess estrogen carried over from puberty, due to a pre-existing medical condition, as a side effect of medications or due to drug abuse [5, 7, 9]. Once there is an excess of estrogen, it sets off a chain reaction by reducing the production of testosterone and lowering metabolism [5]. Excess estrogen will also signal the body to retain more fat in the chest and in the abdomen. When fat is stored in the chest and abdomen, they secrete an enzyme called aromatase that converts testosterone to estrogen [10]. So pectoral fat in effect becomes a secondary gland that produces estrogen. Once the estrogen levels go above a certain threshold, it signals the body to develop breast tissue and this is how gynecomastia is caused.

Other Causes Of Gynecomastia

using recreation drugs like marijuana can be one of the causes of gynecomastia

Marijuana Can Cause Gynecomastia

There used to be a time when the relationship between marijuana as one of the causes of gynecomastia was not well established [12] but these days, physicians are starting to see a direct and definite relationship between smoking marijuana and gynecomastia [5,7]. Doctors are also seeing a pattern where a majority of their patients coming in have continuously used marijuana. Smoking marijuana is also one of the reasons why gynecomastia in teenagers which must be gone as enter adulthood persists and become permanent. Elements in marijuana alters the hormonal mechanism in the body leading to estrogen conversion and gynecomastia [7].

What You Eat Can Cause Gynecomastia

eating foods that are rich in estrogen can also be one of the secondary causes of gynecomastia

Unbeknownst to us until now, a number of the food items that we eat on a daily basis and see on the menu are full of estrogens and drives up the estrogen levels in the body. This is very true in the case of consuming milk from pregnant cows [13]. Some food items like soy [14, 15] and tofu are also rich in estrogen. However, having these food items once in a while will not cause gynecomastia. But that being said, if you already have high levels of estrogen in your body, having these foods act like a double whammy and aid other causes of gynecomastia.

List Of Food Items That Contain Estrogen

No: Description
1 Soy beans and soy products
2 Oats
3 Beans
4 Rice
5 Sesame seeds
6 Apples
7 Rice bran
8 Carrots
9 Coffee
10 Tempeh
11 Tofu [16,17,18]

Medical Conditions That Can Cause Gynecomastia

pre-existing medical conditions can also be one of the causes of gynecomastia

In some men, the causes of gynecomastia can be one of the many medical conditions contributes to breast tissue growth. Medication or a combination of medications that they have been following can also be causing breast tissue growth. From time to time, researchers are also finding out about new medications that have the potential to cause gynecomastia as evident from the recent controversy and lawsuit around the drug Risperdal [19].

Klinefelter Syndrome

One of the classic examples of a medical condition that can cause gynecomastia is Klinefelter Syndrome. This syndrome is characterized by a chromosomal anomaly with men having an additional X chromosome. Studies have shown that men with this medical condition have gynecomastia as a common symptom [20].


The thyroid gland is responsible for the production of thyroid hormones and hyperthyroidism occurs when this gland becomes over-active. Hyperthyroidism is gender neutral and can happen to both men and women but in men, it is considered one of the causes of gynecomastia. Early recognition of this condition and timely intervention have been found to successfully reverse gynecomastia [21].

Kidney Failure

Kidney failure is one of the medical conditions that can cause gynecomastia. When our kidneys are unable to do their normal filtering process, it triggers a series of bodily reactions and hormonal dysfunction is one of them. The end result is a suppression of the production of Testosterone. In this scenario, estrogen levels tip the hormonal balance causing gynecomastia [22].


Malnutrition is one of the often misunderstood and underrated medical conditions that can cause gynecomastia. When our body is devoid of the amount of nutrition that it requires, it reduces the production of testosterone but at the same time, there is no change in the level of estrogen. In this way, malnutrition becomes one of the causes of gynecomastia [1].

Medications That  Could Cause Gynecomastia

an image showing that some medication can also cause gynecomastia

Known or unknown medications can be one of the causes of gynecomastia and this is why a detailed history collection by your doctor specializing in the treatment of gynecomastia is important. There is a real dearth of knowledge among the common folks about the side effects of medication. The most common categories of medications that can cause gynecomastia includes anti-retrovirals, medication regiments that are part of prostate cancer therapies and anti-psychotics. The following list of medication that could cause gynecomastia has been compiled by Gretchen Dickson, MD and published at the Association of American Family Physician website.


No: Description Of Medication
1 Alkylating agents
2 Bicalutamide (Casodex)
3 Cimetidine (Tagamet)
4 Cisplatin
5 Flutamide
6 Isoniazid
7 Ketoconazole
8 Methotrexate
9 Metronidazole (Flagyl)
10 Omeprazole (Prilosec)
11 Penicillamine (Cuprimine)
12 Ranitidine (Zantac)
13 Spironolactone (Aldactone)
14 Anabolic steroids
15 Diazepam (Valium)
16 Digoxin
17 Estrogen agonists
18 Gonadotropin-releasing hormone agonists
19 Human chorionic gonadotropins
20 Phenytoin (Dilantin)
21 Phytoestrogens
22 Diazepam
23 Phenytoin
24 Haloperidol
25 Metoclopramide (Reglan)
26 Phenothiazines
No Medications Whose Mechanism Of Action Causing Gynecomastia Is Unknown 
1 Amiodarone
2 Amlodipine (Norvasc)
3 Angiotensin-converting enzyme inhibitors
4 Antiretroviral agents
5 Atorvastatin (Lipitor)
6 Didanosine (Videx)
7 Diltiazem
8 Etomidate (Amidate)
9 Fenofibrate (Tricor)
10 Finasteride
11 Fluoxetine (Prozac)
12 Heroin
13 Methadone
14 Methyldopa
15 Minocycline (Minocin)
16 Minoxidil
17 Mirtazapine (Remeron)
18 Nifedipine (Procardia)
19 Nilutamide (Nilandron)
20 Paroxetine (Paxil)
21 Reserpine
22 Risperidone (Risperdal)
23 Rosuvastatin (Crestor)
24 Sulindac (Clinoril)
25 Theophylline
26 Tricyclic antidepressants
27 Venlafaxine (Effexor)
28 Verapamil

Causes Of Gynecomastia In Steroid Users

Steroid use without properly flushing it out is also one of the causes of gynecomastia [25, 26]

steroid use without properly flushing it out is also one of the causes of gynecomastia

Steroid users are one of the sub groups among men who have gynecomastia. I want to make it clear that the use of steroid in itself is not one of the causes of gynecomastia rather, the un-systematic use of it is what causes gynecomastia. If you scout the various body-building forums online, you can thread after thread of horror stories by steroid users who have developed gynecomastia. They cycle on with anabolic steroids for continuous periods of time and does not cycle of periodically and flush out the excess estrogens through post cycle therapy. Some steroid users do not cycle off at all, inviting breast tissue growth. Users of anabolic steroid users must take precautions to control the excess estrogen, cycle off and flush out excess estrogens to prevent water retention, gynecomastia and a whole lot of other issues.

an illustration showing a steroid user with gynecomastia

When a steroid user starts his cycle, the natural hormonal balance in his body is altered by suppression of the production of the male hormone testosterone. So the testosterone (male hormone) estrogen (female hormone) balance is tilted and estrogen dominance happens in the body. This triggers a series of chain reaction culminating in the development of gynecomastia. Not providing your body with necessary supplements during cycling and not executing a well balanced PCT are the major causes of gynecomastia among body builders. If you want to learn more, read the post cycle therapy to prevent gynecomastia page.

Medical Review Team

Medical reviewer at Gynecoma.comThe content of this page was fact-checked and medically reviewed by Dr.Sergii Vasyliuk MD on October 22, 2018. You can read more about Dr.Sergii Vasyliuk MD and his credentials at our about us page.

The content of this page was fact-checked and medically reviewed by Dr.Marija Petkovic MD on December 19, 2018. You can read more about Dr.Marija Petkovic MD and her credentials at our about us page.



Suggested Further Reading

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causes and frequently asked questions about gynecomastia in teenagers

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what is man boobs

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a comprehensive guide to post cycle therapy to get rid of gynecomastia

the main requirements to get insurance coverage for gynecomastia surgery

A-Z guide to pseudogynecomastia

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