DPYD and hyperinsulinemic hypoglycemia, familial, 4: The postulated causative mechanisms involved in 5-FU cardio-toxicity are the following: an autoimmune response to damaged cells; an increased oxygen demand in patients receiving 5-FU; a coronary spasm caused by protein kinase C-mediated vasoconstriction; dihydropyrimidine dehydrogenase deficiency (Milano et al, 1999) and the 5-FU contaminant fluoroacetate.