Beta-endorphin levels are reduced in peripheral blood mononuclear cells of cluster headache patients

Opioid system hypofunction has been postulated in cluster headache (CH) on the basis of reduced opioid levels found in the cerebrospinal fluid (CSF). In this study beta-endorphin levels were monitored in the peripheral blood mononuclear cells of 65 episodic CH patients (32 in remission and 33 in cluster period) and 50 healthy controls. Beta-endorphin levels were significantly lower than controls in CH patients experiencing both phases of the illness (ANOVA, p <0.0001). The persistence of this abnormality during pain-free remission suggests a primary alteration in the regulation of beta-endorphin in peripheral blood mononuclear cells. We speculate that these findings reflect reduced CNS levels of beta-endorphin in CH.