Etiology and Risk Factors

Abstract

The etiology of Hashimoto's thyroiditis (HT) arises from an interaction between genetic and non-genetic factors. The genes implicated vary in different ethnic groups and the incidence is increased in people with chromosomal disorders. HT is usually associated with auto-antibodies against thyroglobulin (Tg) and thyro-perioxidase (TPO) leading to primary hypothyroidism. Having other autoimmune diseases is a risk factor to develop HT. First-degree relatives of persons with HT have greater risk of developing the disease. Female gender is associated with an eight-fold increased risk for HT possibly due to the effects of sex hormones, X-chromosome-encoded susceptibility, skewed X-chromosome inactivation, pregnancy, and fetal micro-chimerism. In genetically susceptible individuals, environmental factors, including high iodine intake, selenium deficiency, infectious diseases, stress, and certain drugs, have been implicated in initiating the autoimmune process. This chapter explores the etiology and risk factors of Hashimoto's disease.