ATTR-CM is caused by a deposition of abnormal misshapen proteins on the heart muscles. This protein, called transthyretin, is normally produced by the liver. Its main function is to transport the thyroid hormone and vitamin A in our bloodstream. Due to either genetic mutation or the ageing process, this transport protein can become misshapen. The abnormal proteins can then be deposited in the heart and various organs, resulting in disease.There are two types of ATTR-CM: