I Am A 43y/o Male With Difficulty Holding And Gaining

I am a 43y/o male with difficulty holding and gaining weight and constant diarrhea while my twin brother is very overweight with constant constipation. I've recently learned of Exocrine pancreatic insufficiency (EPI) and will be contacting my doctor for further discussion. Because my brother and I are experiencing such drastic differences in our symptoms I'd like to know if there are other problems of the pancreas that can cause his symptoms which are so opposite of mine. Are there other diseases that may cause an "overactive" pancreas whereas EPI seems to be an "under active" pancreas?