What causes male breast enlargement?

Several conditions : Of course genetics play the greatest role. The incidence has been cited as effecting anywhere from 30-70% of males followed by resolution in nearly 80% after 2 years. The risk is increased in males who are obese or may be taking medications which effect their estrogen to testosterone ratios such as marijuana, spironolactone, steroids, prostate cancers medications, cimetidine, etc.

LOTS OF THINGS: Most has to do with weight gain, but muscle building steroids and pills, marijuana and some medications can do it. Also, certain cancers including testicular cancer can cause it as well. See your regular doctor to check.