CASZ1 and Hyperammonemia: They confirm central predictions of the CASTOR hypothesis in an inborn error of acyl-CoA metabolism: they demonstrate chronically abnormal levels of tissue acyl-CoAs, which intensify during stress, and provide the most complete evidence to date for a direct role of acyl-CoAs in the cardinal signs of hypoglycemia and hyperammonemia common to many inborn errors of acyl-CoA metabolism.