What are the main things that cause man boobs?

I’ve never really been overweight. I put on a few pounds in college like most people, but I’ve always considered myself normal weight. I suffer from man boobs though and I want to know what causes this. Is it just genetic? My dad doesn’t have man boobs.

KVN1001

M, 43, South Dakota

Gynecomastia, or "man boobs", is due to excess breast tissue in a male.  Causes include hormonal imbalances, medication side-effects,  and genetics.  Many cases are "idiopathic", which means you have it and we don't know why you have it.  Fortunately, gynecomastia is very correctible with a simple surgical procedure.  After ruling out other causes of the gynecomastia, the surgical procedure involves a small incision with removal of the breast tissue, and often liposuction to contour the surrounding areas.  It is an outpatient procedure with a 5-7 day recovery.