Clinical relevance of environmental factors in the pathogenesis of autoimmune thyroid disease

Abstract

Genetic factors contribute for about 70% to 80% and environmental factors for about 20% to 30% to the pathogenesis of autoimmunethyroid disease (AITD). Relatives of AITD patients carry a risk to contract AITD themselves. The 5-year risk can be quantifiedby the so-called Thyroid Events Amsterdam-score, based on serum thyroid-stimulating hormone, thyroid peroxidase(TPO)-antibodies and family history. Subjects at risk may ask what they can do to prevent development of AITD. This reviewsummarizes what is known about modulation of exposure to environmental factors in terms of AITD prevention. To stop smokingdecreases the risk on Graves disease but increases the risk on Hashimoto disease. Moderate alcohol intake provides someprotection against both Graves and Hashimoto disease. Low selenium intake is associated with a higher prevalence of thyroid autoimmunity,but evidence that selenium supplementation may lower TPO antibodies and prevent subclinical hypothyroidism remainsinconclusive. Low serum vitamin D levels are associated with a higher prevalence of TPO antibodies, but interventionstudies with extra vitamin D have not been done yet. Stress may provoke Graves hyperthyroidism but not Hashimoto thyroiditis.Estrogen use have been linked to a lower prevalence of Graves disease. The postpartum period is associated with an increasedrisk of AITD. Taking together, preventive interventions to diminish the risk of AITD are few, not always feasible, and probably oflimited efficacy.