They can give him Testosterone if needed. An endocrinologist can do a full panel and check him out to see if something is causing this. Also, check his thyroid too.
One thing to do is to stop eating GMO foods. They have been proven to cause these problems. Soy in particular and corn have been modified and can cause large amounts of estrogen. - Doctors more than ever before are prescribing Testosterone - possibly due to the fact that everyone is eating modified foods. :(
Try starting counseling as well for the depression and Gynecomastia. The gynecomastia leads to body disturbances for males especially at a young age. This can be causing a big part of the depression. Also talk to the health care provider about weight and see if this could have something to do about the low testosterone levels.