Plasma serotonin increase during episodes of tension-type headache.

The mechanisms of tension-type headache remain to be determined. Biochemical abnormalities have been rarely demonstrated. We performed a controlled study of 5-hydroxytryptamine (5HT) in platelet poor plasma obtained from 13 female patients during and between episodes of tension-type headache. The 5HT concentration in patients free of headache was not different from controls, whereas a significant increase in 5HT concentration was seen during headache (p < 0.02). This finding is attributed to release of 5HT from platelets or disordered 5HT metabolism during headache attacks, possibly related to pain in the latter case. We conclude that 5HT may be involved in the pathogenesis of tension-type headache but by different mechanisms than migraine.