MTHFR and hyperinsulinemic hypoglycemia, familial, 4: Values reported in adolescent/adult onset MTHFR deficiency were consistently above 100 μM (4.5 < N < 15), even for very late onset patients, strongly evoking a genetically-sustained metabolic defect, and notvitamins or renal filtration deficiencies, which can also be associated withhyperhomocysteinemia.