What are the different ways a person can end up with an enlarged heart?

Many: A big heart is often a weak heart or a cardiomyopathy. These can come from coronary disease, valvular disease, metabolic issues like thyroid disease, toxins, drugs and alcohol, iron overload, hiv, hepatitis, and sometimes for unknown reasons -- just to name a few. Seeing a cardiologist is recommended.

Many causes: Dr. Freeman is correct. In addition, all fat people and all serious aerobic athletes have big hearts. High blood pressure when treated will let the heart return to normal size unless the person also exercises. There's a host of diseases, each much less common than the lifestyle causes. By itself, it means nothing.