HADH is part of the 3-hydroxyacyl-CoA dehydrogenase enzyme family. HADH is involved in mitochondrial matrix to catalyze the oxidation of straight-chain 3-hydroxyacyl-CoAs as part of the beta-oxidation pathway. HADH enzymatic activity is at its peak with medium-chain-length fatty acids. Mutations in HADH cause familial hyperinsulinemic hypoglycemia. HADH participates in fatty acid oxidation, where some enzymes work in a step-wise fashion to break metabolize fats and convert them to energy.