Alternative names: Hashimoto's Thyroiditis, Hashimoto's Disease, Autoimmune Thyroiditis, Chronic Lymphocytic Thyroiditis
Thyroiditis is an inflammation – not an infection – of the thyroid gland. Hashimoto's thyroiditis is the most common type of thyroiditis and manifests itself as a painless, diffuse enlargement of the thyroid gland occurring predominantly in middle-aged women. Thyroid function is often normal, but hypothyroidism may develop, and rarely, hyperthyroidism. Often, autoantibodies (antibodies your body makes against itself) are present.
Postpartum thyroiditis is the most common thyroid disease to occur after delivery and results in temporary hyperthyroidism or hypothyroidism. Some 5-7% of women worldwide develop the disease after giving birth, according to the American Thyroid Association.
When the thyroid becomes inflamed, it will first emit larger quantities of thyroid hormone into the bloodstream (hyperthyroidism). During this phase, most women are unaware of any symptoms, which are often mild and short-lived. Once this initial phase passes, a woman either recovers completely or has sustained damage to her thyroid. If the thyroid gland was damaged, this damage – together with a depleted reservoir of thyroid hormones – can lead to hypothyroidism. This condition also may clear up or result in further damage and complications. Postpartum thyroiditis symptoms usually do not appear until three to eight months after childbirth. Symptoms are also often mistaken for normal signs of recovery from childbirth.
Hashimoto's disease may rarely be associated with other endocrine disorders caused by the immune system. When Hashimoto's disease occurs with adrenal insufficiency and type 1 diabetes mellitus, the condition is called type 2 polyglandular autoimmune syndrome (PGA II).
Less commonly, Hashimoto's disease occurs with hypoparathyroidism, adrenal insufficiency, and fungal infections of the mouth and nails in a condition called type 1 polyglandular autoimmune syndrome (PGA I).
The onset of the disease is slow, and it may take months or even years for the condition to be detected. Chronic thyroiditis is most common in women and individuals with a family history of thyroid disease. It is estimated to affect between 0.1% and 5% of all adults in Western countries.
Hashimoto's thyroiditis occurs when autoantibodies attack the thyroid tissue, confusing it with a foreign substance. Theories about why this occurs emphasize a basic abnormality in the immune system, which in many patients somehow allows autoimmunity to develop against thyroid tissues as well as other tissues, including those of the stomach, adrenal glands and ovaries. Other autoimmune diseases are frequently seen in these patients, such as rheumatoid arthritis, SLE (lupus), and Sjogren's syndrome.
Some researchers believe that Hashimoto's thyroiditis, primary myxedema and Graves' disease (hyperthyroidism) are different expressions of a basically similar autoimmune process, and that the clinical appearance reflects the immune response in that particular patient.
Diagnosis is made by the finding of a painless, smooth, firm goiter in a young woman, with positive levels of anti-thyroid hormones and a euthyroid (normal thyroid) or hypothyroid metabolic status. Since progression of symptoms may be subtle, thyroiditis is difficult to diagnose at times.
A patient with a small goiter and euthyroidism does not require therapy unless the TSH level is elevated. The presence of a large gland, progressive growth of the goiter, or hypothyroidism indicates the need for replacement thyroid hormone. Surgery is rarely indicated. Development of a lymphoma, though very unusual, must be considered if there is growth or pain in the involved gland.
People with celiac disease are more likely to develop Autoimmune Thyroid Disease (ATD) than the general public, and the reverse is also true. Consuming gluten triggers an autoimmune process in those with celiac disease, causing the immune system to attack the body itself. In the case of ATD, the target of the attack is thyroid gland, resulting in a deficiency or excess of hormones, which causes unpredictable metabolic changes. The most common type of ATD is hypothyroidism.
In one study, 83 patients with autoimmune thyroid disorder were screened for celiac disease. Three patients with asymptomatic celiac disease were found along with one who had previously been diagnosed, giving an overall frequency of 4.8%. By contrast, only one of 249 age- and sex-matched blood donors was found to have celiac disease.
A study of 91 patients with rheumatoid arthritis found 29 patients had evidence of thyroid dysfunction compared to 10 of the 93 controls. The excess thyroid dysfunction was due to either hypothyroidism or Hashimoto's thyroiditis. In this study, thyroid dysfunction is seen at least 3 times more often in women with rheumatoid arthritis than in women with similar demographic features with non-inflammatory rheumatoid diseases such as osteoarthritis and fibromyalgia. [Annals of Rheumatic Diseases, 1993;52 pp.454-456]
Amongst patients with chronic hives and either treated hypothyroidism or a normally functioning thyroid gland, it is reasonable to test for anti-thyroid antibodies. In a study of 10 patients with chronic hives, thyroxine (T4) was administered for a minimum of 12 weeks. Of 7 patients with elevated anti-thyroid antibodies at baseline, all had complete resolution of hives or marked improvement within 4 weeks. Two patients required an increase in the thyroxine before complete resolution was seen. In 2 others, already on thyroxine therapy for hypothyroidism, an increase in the dose also resulted in resolution of the hives.
The initial dose was on average 100mcg per day, which was increased if the initial dose failed to produce clinical improvement. The highest dose used was 250mcg per day. The 3 patients without elevated anti-thyroid antibodies did not respond to thyroxine therapy. There was a recurrence of hives after treatment was stopped which resolved again after treatment was restarted. There was no consistent correlation between improvement in symptoms and reduction in thyroid antibody levels. [J Allergy Clin Immunol 1995;96: pp.901-5]
A study of 132 pairs of twins (264 subjects) showed that smoking can have negative effects on the endocrine system, causing a 3- to 5-fold increase in the risk of all types of thyroid disease. The association was most pronounced in autoimmune disorders (Graves' disease and autoimmune thyroiditis), although there was still a strong association for non-autoimmune thyroid disorders.
Three months of supplementation with 200mcg selenium daily reduced thyroid peroxidase antibodies (TPOAb) but had no effect on Tg antibodies (TgAb) in a well-controlled study of 70 women with autoimmune thyroiditis. TPOAb and/or TgAb levels were above 350 IU/ml. [ J Clin Endocrinol Metab 2002;87(4): pp.1687-1691]
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