Aka gyno , the abnormal breast developement in males , is common. About 95% of boys entering puberty experience it to some degree. It is usually harmless except psychologically, yet frequently unexplainable. Testosterone deficiency is certainly related to many cases ; gyno is often one of the side effects of subnormal testosterone production.

However breasts may enlarge when testosterone levels are normal because of high estrogen secretions. Even when both are normal , pituitary hormones can trigger gyno.

The man experiencing excess breast developement should undergo tests to determine the reason, even if he is not particularly concerned with his appearance. Gynecomastia might indicate an endocrine tumor , and an early diagnosis can be lifesaving.