Although this test does not provide information about the flux through the beta-oxidation system, since the end products of beta-oxidation are not measured, the test provides information about VLCFA metabolism and allows detection of peroxisomal disorders with a defect in peroxisomal beta-oxidation of VLCFAs (ZSD, X-ALD, ACOX1 and DBP deficiency). The gene discussed is ACOX1; the disease is hyperinsulinemic hypoglycemia, familial, 4.