Autoimmune Thyroid Disease: Mechanism, Genetics and Current Knowledge

Recent epidemiological studies recognized a steady increase in the incidence of different autoimmune endocrine disorders, including autoimmune thyroid disease (AITD). The etiology of AITD is multifactorial and involves genetic and environmental factors and apparently with a strong preponderance in females. There are mainly two types of AITD, Graves' disease and Hashimoto's disease and both of these show strong association in age groups above 45-50 years. Among environmental factors smoking and alcohol have significant effects, both protective as well as for aggravating the disease, even though the precise nature of these effects are not clearly known. There are elevated levels of circulating antibodies against the thyroid proteins, mainly thyroid oxidase, thyroglobulin and thyroid stimulating hormone receptor, in patients with Graves' disease or Hashimoto's disease. Linkage and association studies in AITD identified several major genes that are relevant for the onset of AITD, including the thyroid-specific genes, thyroglobulin and thyroid-stimulating hormone receptor and also many immune-regulatory genes. In this review we addressed many aspects of AITD including disease mechanisms, involved thyroid antigens, environmental factors and genetic factors.