Symptoms in Euthyroid Hashimoto's Thyroiditis: Is There a Role for Autoimmunity Itself?

The possible effect of autoimmunity per se on general health and overall quality of life of women with Hashimoto's thyroiditis (HT) has been recently evaluated by Ott J et al. In 426 euthyroid women, the authors evaluated either the quality of life or symptom load with regard to both histological diagnosis of thyroiditis and serum anti-thyroid peroxidase (anti-TPO) antibody levels. The authors found that women with positive anti-TPO titer reported a significantly higher prevalence of general health symptoms as compared to those without HT. Besides the histological thyroiditis grade, anti-TPO levels were positively correlated with the symptom score. Moreover, higher anti-TPO levels were associated with a quality of life, despite levothyroxine supplementation. The authors conclude that women with HT suffer from a high symptom load independently from hypothyroidism, which results just a contributing factor to the development of the clinical syndrome. In agreement with these results, we recently reported on the presence of symptoms and signs consistent with fibromyalgia (FM) in patients with HT regardless thyroid dysfunction, focusing to the weight of anti-thyroid autoimmunity in the HT-associated clinical syndrome. Indeed, FM comorbidity resulted in almost one third of patients (all females) suffering from HT with or without mild hypothyroidism (SCH). Moreover, the prevalence of fibromyalgia was slightly higher in euthyroid HT patients (33.3%) than in those suffering also from SCH (28.5%). In this setting, it is noteworthy that SCH patients without autoimmunity did not show any clinical symptom consistent with FM. Therefore, our data support the hypothesis that thyroid autoimmunity per se plays a role in the development of FM comorbidity, although the specific underlying mechanism is still not completely known. So far, HT is commonly considered a well-defined clinical entity and it is widely assumed that hypothyroidism at various degree is the main, if not the only cause of the broad clinical spectrum. However, our data and those from the study by Ott et al. share new insights into the patho-physiological features of Hashimoto's thyroiditis with special reference to the peculiar role of autoimmunity per se, thus leading to a novel understanding of this apparently well-defined disease.