Review of Overlap Between Thermoregulation and Pain Modulation in Fibromyalgia

Fibromyalgia syndrome is characterized by widespread pain that is exacerbated by cold and stress but relieved by warmth. We review the points along thermal and pain pathways where temperature may influence pain. We also present evidence addressing the possibility that brown adipose tissue activity is linked to the pain of fibromyalgia given that cold initiates thermogenesis in brown adipose tissue via adrenergic activity, while warmth suspends thermogenesis. Although females have a higher incidence of fibromyalgia as well as more resting thermogenesis, they are less able to recruit brown adipose tissue in response to chronic stress than males. In addition, conditions that are frequently comorbid with fibromyalgia compromise brown adipose activity making it less responsive to sympathetic stimulation. This results in lower body temperatures, lower metabolic rates, and lower circulating cortisol/corticosterone in response to stress - characteristics of fibromyalgia. In the periphery, sympathetic nerves to brown adipose also project to surrounding tissues, including tender points characterizing fibromyalgia. As a result, the musculoskeletal hyperalgesia associated with conditions like fibromyalgia may result from referred pain in the adjacent muscle and skin.