Hexanoyl glycine is an acylated amino acid that is used as a urinary biomarker for several indications. It is normally biosynthesized from hexanoyl-CoA and glycine by the mitochondrial enzyme glycine N-acyltransferase. Increased urinary excretion of hexanoyl glycine in humans is indicative of a deficiency in medium-chain acyl-CoA dehydrogenase. Increased urinary hexanoyl glycine can also be used as a biomarker for exposure to gamma radiation. Levels of hexanyl glycine can also be elevated during cancer, while they are decreased 20-fold in mice following treatment with the PPARα ligand Wy 14643.