Inadequate Thyroid Hormone Regulation as the Main Mechanism of Fibromyalgia: A Review of the Evidence

All symptoms and most objectively verified abnormalities among fibromyalgia (FMS) patients are characteristic of subsets of patients with hypothyroidism or partial peripheral thyroid hormone resistance. Laboratory tests have shown a higher-than-normal incidence of thyroid disease among FMS patients. Among 40 objectively verified abnormalities that also occur in hypothyroidism and peripheral thyroid hormone resistance, FMS patients have abnormally low resting metabolic rates and basal body 4 temperatures. In several open and blinded treatment trials, thyroid hormone therapy other than T -replacement has reduced or eliminated FMS symptoms and many study patients have ceased to meet the criteria for FMS. In addition, a 1-to-5-year follow-up study showed that patients treated with thyroid hormone remained improved and used fewer medications to control symptoms than did matched untreated controls. These study findings constitute rigorous testing of, yet failure to refute, the inadequate thyroid hormone regulation etiological hypothesis of FMS. Competing etiological hypotheses of FMS account for only a fraction of the symptoms and objectively verified abnormalities among patients, and no treatment other than thyroid hormone therapy has been shown to relieve patients of FMS status. This review of the published research literature shows that inadequate thyroid hormone regulation is the most likely underlying mechanism of the symptoms and objective abnormalities of patients who meet the criteria for FMS. 3 4,