Sally P. Stabler

Adverse Event Associated With Methionine Loading Test: A Case Report

The death of a control subject after an oral load of methionine for a study of the possible relationship between homocysteine and Alzheimer’s disease is reported. The subject developed postload plasma concentrations of methionine far beyond those reported previously in humans given the usual oral loading dose of methionine (100 mg/kg body wt). Her preload plasma metabolite values rule out known genetic diseases that might predispose one to unusually high methionine concentrations. The most likely explanation for these events is that the subject received a substantial overdose of methionine. The possibility that extremely high methionine concentrations may lead to severe cerebral effects is discussed, and it is recommended that any move to increase the sensitivity of the usual methionine loading test by increasing the dose of methionine either not be undertaken or be taken only with extreme care.

Homocysteine and Other Metabolites in the Diagnosis and Follow-Up of Cobalamin and Folate Deficiencies

The development and clinical application of new assays for serum metabolites of vitamin B12 and folate have resulted in advances that allow for better diagnosis and differentiation between deficiencies of the two. This is particularly important given the high prevalence of subclinial B12, folate, and possibly pyridoxine deficiency in the elderly.