What causes “man boobs”? January 25, 2023 Men can develop gynecomastia in any phase of life—in fact, most men are born with excess tissue due to increased estrogen from their mother. However, this tends to decrease naturally a few weeks after birth. At the root, hormone imbalance is the cause of gynecomastia, whether that imbalance happens during puberty or is caused by certain medications, health conditions, or other lifestyle factors. Of all men in Houston and across the country, about half of them will experience enlarged breasts during their lifetime. Though sometimes the appearance of “man boobs” resolves on its own, oftentimes prescription medication and/or breast reduction surgery will be the most effective treatment.