The Incidence of Autoimmune Thyroid Disease: A Systematic Review of the Literature

Anita McGrogan; Helen E. Seaman; John W. Wright; Corinne S. de Vries

Disclosures

Clin Endocrinol. 2008;69(5):687-696. 

In This Article

Summary and Introduction

Summary

Objective: To undertake a systematic review of literature published between 1980 and 2008 on the incidence of autoimmune thyroid disease.
Design: All relevant papers found through searches of Medline, EMBASE and ScienceDirect were critically appraised and an assessment was made of the reliability of the reported incidence data.
Results: The reported incidence of autoimmune hypothyroidism varied between 2·2/100 000/year (males) and 498·4/100 000/year (females) and for autoimmune hyperthyroidism, incidence ranged from 0·70/100 000/year (Black males) to 99/100 000/year (Caucasian females). Higher incidence rates were found in women compared to men for all types of autoimmune thyroid disease. The majority of studies included in the review investigated Caucasian populations mainly from Scandinavia, Spain, the UK and the USA. It is possible that nonautoimmune cases were included in the incidence rates reported here, which would give an overestimation in the incidence rates of autoimmune disease presented.
Conclusion: To our knowledge this is the most comprehensive systematic review of autoimmune thyroid disease conducted in the past two decades. Studies of incidence of autoimmune thyroid disease have only been conducted in a small number of mainly western countries. Our best estimates of the incidence of hypothyroidism is 350/100 000/year in women and 80/100 000/year in men; the incidence of hyperthyroidism is 80/100 000/year in women and 8/100 000/year in men.

Introduction

Endocrine disease of the thyroid may result in either under- or overactivity of the gland and may be due to congenital factors, inadequate levels of dietary iodine intake, pregnancy, radiotherapy, viral infection, surgery, underlying disease such as infiltrative disorders, or autoimmunity.[1,2,3,4,5] The incidence of thyroid disease caused by iatrogenic factors and iodine deficiency is clearly determined by environmental and clinical factors.[6] However, the pathogenesis of autoimmune thyroid disease is poorly understood although genetic factors are clearly important in both Graves' disease and autoimmune hypothyroidism.[7] Insight into the incidence of disease is important for the identification of trends in relation to patient characteristics such as sex and geographical location and to determine any changes in incidence following the introduction of new environmental factors.

Previous reviews on the epidemiology of thyroid disease have evaluated the incidence and prevalence of the different types of thyroid disease, with emphasis being given to the well-known Whickham study from the UK.[1,6,8,9] Other subject areas covered include the prevalence of subclinical hyper- and hypothyroidism,[2] the epidemiology of hypothyroidism[10,11] and thyrotoxicosis.[11] Typically, the prevalence of hypothyroidism has been found to be between 0 and 7·8/1000 men and between 0 and 20·5/1000 women, and for hyperthyroidism, between 2·0 and 19·4/1000 women.[11] To our knowledge, no systematic investigation of the incidence of all types of autoimmune thyroid disease has been conducted within the past two decades. This literature review critically appraises relevant published work on the incidence of primary autoimmune thyroid disease classified clinically as hypothyroidism, hyperthyroidism, thyrotoxicosis, Graves' disease or Hashimoto's thyroiditis throughout the world.

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