Aetiology of thyroid autoimmunity

Abstract

Autoimmune thyroid disease (AITD) is characterised by the development of thyroid autoantibodies, mainly anti-thyroid peroxidase antibodies, anti-thyroglobulin antibodies (primarily involved in the development of Hashimoto’s thyroiditis [HT]) and thyroid stimulating hormone receptor antibodies (mostly involved in the development of Graves’ disease [GD]). While genetic factors provide 70 to 80% of the risk for the development of thyroid autoimmunity (TAI), environmental factors contribute about 20 to 30% to the immunopathogenesis of AITD. Such environmental factors include smoking (predisposes to GD but protects against HT), alcohol (moderate consumption protects against both HT and GD), stress (predisposes to GD) and iodine (possibly increases risk of AITD). Low selenium and vitamin D levels might increase the risk of TAI, although data remains indeterminate and selenium supplementation did not always improve TAI in clinical studies. Additionally, certain drugs, toxic chemicals, infections, birth in winter and autumn and radiation exposure have also been implicated in the development of TAI. Preventive interventions to decrease the risk of AITD are limited and not always feasible, though personal and public health interventions might help with smoking and iodine exposure.