Gynecomastia in males is caused by an imbalance between the hormones estrogen and testosterone. It can also be due to genetic causes as well as being overweight. Normally, men produce small amounts of estrogen, the hormone that controls breast growth. However, if a man’s body produces too much estrogen or has low testosterone levels, it can increase breast gland tissue. Other causes of gynecomastia may include medication side effects, such as certain antidepressants, antibiotics, chemotherapy, prostate cancer medicines, ulcer or cardiovascular medicines, as well as certain medical conditions such as liver or lung cancer, cirrhosis of the liver, overactive thyroid, or hormone problems such as cancer of the pituitary gland, adrenal glands, or testicles. Alcohol, marijuana, methamphetamine, and heroin use can also cause gynecomastia. In some cases, gynecomastia can be a side effect of renal failure or malnutrition.