Man boobs, moobs, and other, less polite terms by which people refer to an overly developed male chest aren’t just a running joke. The medical term for the condition is gynecomastia—the growth of breast tissue in men. Although many people associate gynecomastia with being overweight or obese, weight gain isn’t the only cause of gynecomastia, although it can certainly come into play. Gynecomastia affects around a third of the male population at some point during their lifetimes and may be a symptom of hormonal imbalance or other, more serious issues.

Hormonal imbalance—caused by a drop in testosterone, an increase in estrogen, or both—can lead to an enlargement of glandular tissue behind the nipples. Usually, there is no major medical issue with gynecomastia, although left untreated, the underlying cause can lead to one. And getting treated for the condition may also help improve overall quality of life.