CALCA and migraine disorder: This is mainly based on clinical observations, including increased CGRP plasma levels during migraine attacks [37,38] (but see also [39]), delayed headache attacks after CGRP infusion in patients suffering from primary headaches [7], and the effective treatment of migraine with CGRP receptor antagonists (like olcegepant/gepants; [40,41,42] and monoclonal antibodies targeting CGRP or its receptor [43].