Melatonin as adjunctive therapy in the prophylaxis of cluster headache: a pilot study.

Background: The periodicity of cluster headache suggests involvement of the suprachiasmatic nucleus of the hypothalamus, the biological clock. The secretion of melatonin, a hormone produced by the pineal gland and regulated by the suprachiasmatic nucleus, is altered in patients with cluster headache. Melatonin shifts circadian rhythms.