While d31-C16 is hardly formed in PBMCs from patients with CPT-I deficiency, d7-C4 is normally formed both in patients with CPT-I deficiency and in controls from d15-OA, which is transported into mitochondria without the action of CPT-I and is metabolized thorough beta-oxidation. This evidence concerns the gene CPT1A and hyperinsulinemic hypoglycemia, familial, 4.