Thyroid function and autoimmunity in β-Thalassemia (β-Thal)
Maria Chiara Cocco1, Francesca Pigliaru1, Stefania Vacquer2, Maria Paola Carta2, Maria Eliana Lai2 & Stefano Mariotti1
Introduction: Primary endocrine failure in β-Thal is caused by iron overload in epithelial cells and in interstitial macrophages. Autoimmune phenomena are not believed to play any significant role, although iron overload, through non-specific inflammatory process, could trigger autoimmunity, as recently suggested for the pathogenesis of diabetes mellitus in β-Thal patients.
Purpose: We investigated thyroid function and anti-thyroid autoantibodies (ATA) in 132 β-Thal patients (94 with β-Thal major, 60 F and 34 M and 38 with β-Thal intermedia, 16 F and 22 M, age range 2845 years) compared with a large age-matched group (1002 subjects) from general population. All β-Thal patients and control subjects come from Sardinia, Italy, where a high the prevalence of both β-Thal and autoimmunity is well documented.
Results: The prevalence of primary overt and subclinical hypothyroidism in β-Thal patients was 28.7% (38/132), without significant difference between M and F; ATA were detected in 3/38 (7.8%) hypothyroid β-Thal patients, a prevalence similar to that observed in euthyroid β-Thal (7/94=7.4%). Although the prevalence of ATA observed in the entire group of β-Thal patients was not different when compared to controls, it is worth noting that the prevalence of ATA in β-Thal women was 7/76=9.2%, a value significantly lower (P<0.01) than that found in control women (81/408=19.8%).
Conclusions: Our study confirms that thyroid autoimmunity has no role in the pathogenesis of hypothyroidism in β-Thal even in Sardinia, where the prevalence of autoimmunity is elevated. Moreover, β-Thal women show a lower ATA prevalence than control women, suggesting a possible role of iron overload as inhibiting rather triggering factor in the development of thyroid autoimmunity.