Gynecomastia is caused by increased estrogen in your body due to Testosterone amortization. The fatty tissue in your chest becomes enlarged (bitch tits) and your nipples becomes sensitive. Gyno can be controlled by controlling estrogen or removal by surgery. The higher your body fat percentage the more likely you will have gyno complication due to Test amortization. Body fat messes with your estrogen. By starting your cycle at a lower body fat, you reduce the chance of gyno. An AI (amortize inhibitor) like arimadex or anastrizole is used during the cycle to reduce the amount of amortize of Test into estrogen. Basically, you need to be lean to be lean. LOL