Is calcitonin gene-related peptide a reliable biochemical marker of migraine?

The aim of this study was to provide an overview of clinical studies on calcitonin gene-related peptide (CGRP) measurements in body fluids of migraine patients and to discuss the validity of CGRP measurement as a clinical biomarker of migraine.Several studies have reported increased CGRP levels in venous blood, saliva and tear fluid of migraine patients compared with healthy controls and in migraine patients during attacks compared with the interictal state, suggesting that CGRP may be a feasible biomarker of migraine. However, the findings of studies investigating CGRP levels in migraine patients are generally conflicting and measurements of CGRP levels are challenged by several methodological issues. Reported differences in CGRP levels between patients with chronic migraine relative to episodic migraine have also been inconsistent. There is also a well documented involvement of CGRP in several nonmigraine pain disorders, including cluster headache and common pain conditions such as osteoarthritis.Current evidence does not justify the usage of CGRP levels as a biomarker for diagnosing migraine or for determining the severity of the disease in individual patients. However, CGRP measurements could prove useful in the future as clinically relevant biomarkers for predicting the response to therapy, including anti-CGRP migraine drugs.