Cluster headache is a primary headache disease, meaning it does not occur as a symptom to another underlying disease. Cluster headaches affect men six times more than women and typically begin between the ages of 20 and 50, according to the Cluster Headache Support Group. Cluster headaches are characterized by episodes of excruciating pain usually behind the eye on one side of the head. These episodes may last from 15 to 180 minutes, and tend to recur at specific times of day, usually while sleeping. Although the exact cause is not known, there are some known triggers and several hypothesis on the cause.
Hypothalamus
The hypothalamus, a small gland in the brain, releases hormones that help to regulate body temperature, food and water intake, sexual behavior and reproduction, psychological cycles, emotional responses and circadian rhythms. Hormones released by the hypothalamus stimulate or inhibit the secretion of hormones by other glands including the pituitary gland. In this way, the hypothalamus links the nervous system to the endocrine system.
Patients who suffer from cluster headaches often have abnormal levels of hormones such as cortisol, melatonin, prolactin and thyroid stimulating hormone in the blood. This implicates the hypothalamus, which directly controls the release of these hormones from the pituitary gland, adrenal gland and pineal gland.
Neurotransmitters
The Mayo Clinic says that changes in the blood levels of some neurotransmitters, chemicals that carry signals to and from the brain, may be responsible for causing cluster headaches. Serotonin is one such neurotransmitter that is predominantly found in the gastrointestinal and central nervous systems. Serotonin regulates mood, appetite, sleep, muscle contractions and cognitive function. How serotonin levels may affect the onset of cluster headaches is not understood, but it is one factor under consideration.
Environmental Triggers
Migraine headaches, which are similar yet different to cluster headaches, are known to have specific triggers. The relationship between triggers and cluster headaches is less understood; however, there are several environmental factors that may affect the onset of episodes.
The consumption of alcohol is the only recognized dietary trigger for cluster headaches, according to information published in the "Orphanet Journal of Rare Diseases." Smoking or breathing in cigarette smoke may also trigger episodes.
Other environmental factors that may affect cluster headaches include altitude, bright sunlight and heat. Certain medications, such as nitroglycerin taken for heart problems, may also trigger cluster headaches.
