Causes of Gynecomastia (Man Boobs)
By Erica Zelfand

Gynecomastia – also known as “Man Boobs” – happens when hormonal imbalances create swelling in the breast tissue.

Most males actually begin life with swollen breasts. Parents of baby boys sometimes express concern at the size and texture of their newborn boys’ breasts, and I am quick to reassure them that it’s a temporary symptom from floating around in mom’s womb and being exposed to all the estrogen made by her placenta for nine months. (This is also, by the way, why the penises of baby boys look so small in proportion to their testicles. Relax, dad, it’ll grow!)

Gynecomastia can also be normal in teenage males as they go through puberty. Last week I saw a mortified 14-year-old boy who was very concerned about his slightly raised nipples. I watched the color return to his face as I promised him that his nipples would get flatter as he continued to develop.

In adult males, however, gynecomastia is a sign of a hormone imbalance, namely:
  • Low testosterone,
  • High estrogen, or
  • Both



Low Testosterone:

Testosterone is made in the testicles. Conditions that interfere with normal testosterone production – such as Klinefelter syndrome, pituitary insufficiency, or other types of hypogonadism – can cause gynecomasia.

Testosterone Replacement Therapy (TRT):

Testosterone is naturally turned into estrogen in the body by an enzyme called Aromatase. Any time a man is put on testosterone therapy his estrogen levels also invariably get a boost. Guys on TRT (testosterone replacement therapy) are therefore at higher risk for developing gynecomastia. For this reason I periodically check estradiol (estrogen) levels in male patients on TRT to catch and correct any imbalances. Sometimes an aromatase inhibitor such as Anastrozole (Arimidex) can be used to slow the body’s conversion of testosterone into estrogen.

A number of herbs and natural agents can help as well, such as flax, grape seed, chrysin, and bioflavonoids.It’s all about balance: having low T can increase the risk of man boobs, and getting un-checked treatment for the low T can cause it too!



Smoking Pot and Drinking Beer:

Certain plants such as hops and cannabis are known as phytoestrogens. Because of their structural similarity with estradiol (a form of estrogen), phytoestrogens mimic the effects of estrogen at receptor sites.

For this reason, guys who smoke pot on a regular basis are more likely to have man boobs, even if they’re generally fit. The same goes for guys who drink beer, as beer is made from hops, another potent phytoestrogen. (Side note: beer is also great at increasing a nursing mother’s milk supply!)

Liver Disease:

Because hormones are conjugated in the liver, diseases affecting the liver can cause gynecomastia and a host of other ailments. This is yet another reason that heavy drinkers are prone to developing man boobs. Many Americans nowadays also have fatty liver disease from eating too many sugars and refined carbohydrates; these guys are prone to gynecomastia as well.


Adipose (fat) cells make estrogen through an enzyme known as aromatase. This means the more fat you have on your body, the higher your estrogen levels will be. For this reason, overweight and obese men have higher estrogen levels, which can result in man boobs.


It’s normal for testosterone levels to drop as men age. In fact, testosterone levels drop by about 1% per year in men after the age of 30. Over time this creates a relatively lower ratio of testosterone to estrogen.


Other causes of gynecomastia include:

  • Methamphetamine (“meth”) use
  • Heroin or methadone use
  • Estrogen-secreting tumors or cancers of the pituitary, adrenals, or testicles
  • Steroids
  • Drugs used to treat ulcers (such as cimetidine)
  • Drugs used to treat epilepsy (like Dilantin)
  • AIDS medications
  • Digitalis
  • Chemotherapy drugs, especially alkylating agents
  • Anti-androgen drugs, such as spironolactone and medications used to treat prostate cancer
  • Antianxiety and antidepressant medicines
  • Hyperthyroidism
  • Kidney failure


Gynecomastia is treatable in many cases.

Thankfully, by balancing hormone levels, losing weight, building muscle mass, and restricting the use of cannabis, alcohol, and certain pharmaceutical drugs, with time gynecomastia can resolve. If the gynecomastia is caused by an underlying condition, then getting treatment for that condition is essential.