Fibromyalgia - Causes

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Stress Hormones. Researchers have also found abnormalities in the hormone system known as the hypothalamus-pituitary-adrenal gland (HPA) axis. The HPA axis controls important functions, including sleep, the stress response, and depression. Changes in the HPA axis appear to produce lower levels of the stress hormones norepinephrine and cortisol. (By contrast, levels of stress hormones in depression are higher than normal.) Lower levels of stress hormones lead to impaired responses to psychological or physical stresses. (Examples of physical stress include infection or exercise.)

Certain factors may inappropriately trigger a person's stress response and contribute to the development of fibromyalgia, including:

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• Infections (Epstein-Barr virus, Lyme disease)
• Physical trauma (such as a car accident)
• Emotional stress
• Hormonal changes (such as an underactive thyroid gland)
• Medications

Click the icon to see an image of the adrenal glands.

Low IGF-1 Levels. Some studies have reported low levels of insulin-like growth factor-1 (IGF-1) in about a third of fibromyalgia patients. IGF-1 is a hormone that promotes bone and muscle growth. Low levels of growth hormone may lead to impaired thinking, lack of energy, muscle weakness, and intolerance to cold. Studies suggest that changes in growth hormone likely stem from the hypothalamus in the brain. Although researchers have not found a link between IGF-1 levels and fibromyalgia, growth hormone levels in the blood may be a marker of the disorder.

Abnormal Pain Perception and Substance P. Some studies have suggested that people with fibromyalgia may perceive pain differently than healthy people. Fibromyalgia may involve too much activity in the parts of the central nervous system that process pain (the nociceptive system). Brain scans of fibromyalgia patients have found abnormalities in pain processing centers. For example, researchers have detected up to three times the normal level of substance P (a chemical messenger associated with increased pain perception) in the cerebrospinal fluid of fibromyalgia patients.