Epidemiology

Epidemiology

DOI: 10.4018/978-1-5225-9655-4.ch002

Abstract

Hashimoto thyroiditis (HT) remains the most common cause of spontaneous hypothyroidism in areas of adequate iodine intake, such as North America. The incidence of HT is estimated to be 10-15 times higher in females. The most commonly affected age range is 30-50 years, with the peak incidence in men occurring 10-15 years later, but it may be seen in any age group, including children. Hashimoto's thyroiditis appears to occur in more than 10% of patients presenting with thyroid nodule and may be associated with other autoimmune disorders. The occurrence of papillary thyroid carcinoma in HT ranges widely from 0.5-30% of cases. The prevalence of thyroid antibodies is twice more common in women than in men, and higher in whites and Asians than Blacks or Mexicans. There is approximately a 30-fold increase in risk for developing HT in children and 20-fold increased risk in siblings of patients with HT, with females being significantly more often affected than males. This chapter explores the epidemiology of Hashimoto's disease.
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Introduction

The most common cause of hypothyroidism Worldwide is iodine deficiency. However, Hashimoto thyroiditis remains the most common cause of spontaneous hypothyroidism in areas of adequate iodine intake, such as North America.

Iodine is a trace element (mineral) with the symbol “I” and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black non-metallic solid at standard conditions that melts to form a deep violet liquid at 114 degrees Celsius, and boils to a violet gas at 184 degrees Celsius (Meija et al., 2016). Iodine is essential in the synthesis of thyroid hormones; thyroxine (T4) and triiodothyronine (T3). The two thyroid hormones regulate the metabolism in every cell of the body. This is required for the development of skeletal and nervous system. Iodine is is naturally present in some foods (Pennington, 1995; Teas, 2004; Dasgupta, 2008), added to others (iodized table salt) (World Health Organization, 2007; Food and Drug Administration, 2009), and available as a dietary supplement (Aquaron, Delange, Marchal, Lognoné, & Ninane, 2002).

Incidence

Worldwide Incidence

The annual incidence of Hashimoto's thyroiditis seen in practice Worldwide is unknown, but is approximately, 0.3-1.5 cases per 1,000 population per year) (Gordin, 1979; Ling, 1969; Tunbridge, 1977; Vanderpump, 1995; Vanderpump, 1998), which is roughly equal to that of Graves' disease (an autoimmune disease that affects the thyroid, frequently resulting in hyperthyroidism and an enlarged thyroid; also known as toxic diffuse goiter).

Incidence in United States

Hashimoto thyroiditis is the most common cause of hypothyroidism in the United States after the age of 6 years, with the incidence estimated to be 1.3% in a series of 5000 children aged 11-18 years. In adults, the incidence is estimated to be 3.5 per 1000 per year in women and 0.8 per 1000 per year in men. Incidence may be as high as 6% in the Appalachian region (Weetman, 2006).

The incidence of Hashimoto's thyroiditis is estimated to be 10-15 times higher in females. The most commonly affected age range is 30-50 years, with the peak incidence in men occurring 10-15 years later, but it may be seen in any age group, including children. The overall incidence of hypothyroidism increases with age in men and women. It is certain that Hashimoto's disease exists with a much higher frequency than is diagnosed clinically, and its frequency seems to be increasing (Meng et al., 2015).

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