Plasma Methionine Enkephalin Levels — A Biological Marker for Migraine?

SYNOPSIS Migraine patients, either during an attack or when pain‐free, have significantly higher platelet‐rich and platelet‐poor plasma methionine‐enkephalin levels than healthy race‐ and sex‐matched and age‐comparable controls. Although we did not observe differences in the platelet‐rich samples between the patients subgroups, platelet‐poor samples had higher peptide levels during a pain‐free period than the values obtained for the patients during a migraine episode. Similarly, platelet‐rich samples obtained from controls and patients during an attack had higher methionine‐enkephalin levels than their corresponding platelet‐poor plasma samples. These results provide new evidence supporting the involvement of the endogenous peptides in the etiology of migraine headache and suggest that plasma methionine‐enkephalin levels could serve as a biological marker for this condition.