Tryptamine levels are low in plasma of chronic migraine and chronic tension-type headache
The primary aim of this study (TA-CH, Tryptophan Amine in Chronic Headache) was to investigate a possible role of tryptophan (TRP) metabolism in chronic migraine (CM) and chronic tension-type headache (CTTH). It is not known if TRP metabolism plays any role in CM and/or CTTH. Plasma levels of serotonin (5-HT), 5-hydroxyindolacetic acid (5-HIAA), metabolite of 5-HT, and tryptamine (TRY) were tested in 73 patients with CM, 15 patients with CTTH and 37 control subjects. Of these, plasmatic TRY was significantly lower in CM (p < 0.001) and in CTTH (p < 0.002) patients with respect to control subjects, while 5-HIAA levels in plasma were within the same range in all groups. 5-HT was undetectable in the plasma of almost all subjects. Our results support the hypothesis that TRP metabolism is altered in CM and CTTH patients, leading to a reduction in plasma TRY. As TRY modulates the function of pain matrix serotonergic system, this may affect modulation of incoming nociceptive inputs from the trigeminal endings and posterior horns of the spinal cord. We suggest that these biochemical abnormalities play a role in the chronicity of CM and CTTH.