Thyroid autoimmunity may represent a predisposition for the development of fibromyalgia?

In our previous study, we observed that the presence of autoimmune thyroid disease worsens fibromyalgia (FM) symptoms. The aims of this study are to evaluate whether there is a predisposition for the development of FM in patients with Hashimoto's thyroiditis (HT) with or without subclinical hypothyroidism (SCH) and in patients with SCH alone and what is the weight of antithyroid antibody positivity and SCH on FM comorbidity. Fifty-two patients, 39 affected by HT with or without SCH and 13 by SCH, were matched with 37 patients affected by FM and 25 healthy subjects. Blood samples were collected from all study subjects for the determination of serum TSH, free triiodothyronine, free thyroxine, antithyroperoxidase antibody (TPOAb), antithyroglobulin antibody (TgAb) and non-organ-specific autoantibodies. Clinical assessment of patients and controls included the "Fibromyalgia Impact Questionnaire" (FIQ), while pain severity was evaluated using a visual analogue scale (VAS). Patients and controls were also characterized by the presence of diffuse pain, fatigue, paresthesiae, muscle spasms, non-restful sleep, tension headache and presence of mood disorders. FM comorbidity resulted in twelve HT subjects (31%) and none in SCH patient. In particular, FM comorbidity in HT patients without SCH was 33.3% and in HT patients with SCH was 28.5%. Based on our data, we speculate that maybe there is more than a hypothesis regarding the cause-effect relation between thyroid autoimmunity and the presence of FM, thus suggesting a hypothetical role of thyroid autoimmunity in FM pathogenesis.

Gain of function TSH receptor mutations and iodine deficiency: implications in iodine prophylaxis.

Iodine deficiency is widely known to be the main cause of nodular goiter (NG). In iodine deficient areas subclinical and overt hyperthyroidism is the major cause of morbidity and it is mainly due to toxic NG rather than Graves' disease. Toxic NG, including toxic multinodular goiter and toxic thyroid adenoma is usually encountered in subjects with long-standing NG, in whom thyrotoxicosis is usually preceded by a long phase of euthyroidism and then subclinical hyperthyroidsm (abnormally low TSH with normal circulating thyroid hormones). Epidemiological studies indicate that, compared to Graves' disease, the incidence and prevalence of non-autoimmune hyperthyroidism due to toxic adenoma and toxic multinodular goiter differ in different regions of the world, being much more frequent in areas of iodine deficiency. Recently, mutations of the TSH receptor (TSHr) gene causing permanent activation of the thyroid follicular cell adenylate-cyclase, have been shown to be the most probable cause of the hyperfunction and growth of toxic adenoma. In this review we will focus our attention on the role of external factors (i.e. iodine deficiency) with respect to individual factors (i.e. genetic mutations) in the pathogenesis of toxic NG.