Hashimoto thyroiditis

The vast majority of hypothyroid patients have thyroid gland failure (primary hypothyroidism). The causes include chronic autoimmune thyroiditis (Hashimoto s disease), iatrogenic hypothyroidism, iodine deficiency, enzyme defects, thyroid hypoplasia, and goitrogens. 

Pituitary TSH suppressants In the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, subacute, or chronic lymphocytic thyroiditis (Hashimoto), multinodular goiter, and in the management of thyroid cancer (except liothyronine). 

Hypothyroidism, known as myxedema in adults, when severe, is the most common disorder of the thyroid gland. Worldwide, hypothyroidism is most often the result of endemic iodine deficiency. In nonendemic areas, where iodine is sufficient in the diet, chronic autoimmune thyroiditis (Hashimoto s thyroiditis) accounts for the majority of cases. This disorder is primarily characterized by high levels of circulating antibodies against a key enzyme (thyroid peroxidase) in the processing of iodine in the thyroid gland. Blocking antibodies directed at the TSH receptor may also be present. Thyroid destruction may also occur via apoptotic cell death. 

Graves ophthalmopathy develops in more than 80% of cases within 6 months of the diagnosis of Graves hyperthyroidism. Graves ophthalmopathy may occasionally develop before the diagnosis of hyperthyroidism. Thyroid-related orbitopathy is associated with Graves hyperthyroidism in 90% of cases and with autoimmime thyroiditis (Hashimoto s disease) in some 5%. No laboratory evidence of thyroid disease is fiaimd in 5% to 10% of patients. This condition is called ophthalmic or euthyroid Graves ophthalmopathy. 

Treatment of thyroiditis (Hashimoto s thyroiditis, subacute thyroiditis of de Quervain). Where hyperthyroidism is a feature, treatment is by a P-adrenoceptor blocking drug. Antithyroid drugs should not be used. Where there is permanent hypothyroidism, the treatment is thyroid hormone replacement. 

Tg is primarily used as a tumor marker in patients carrying a diagnosis of differentiated thyroid carcinoma (DTC). Although serum Tg is elevated in patients with thyroid cancer, including thyroid follicular and papillary carcinoma, elevations are also are seen in nonneoplastic conditions such as thyroid adenoma, subacute thyroiditis, Hashimoto s thyroiditis, and Graves disease. Serum Tg concentrations are not increased in patients with medullary thyroid carcinoma. 

Thyroid Hypofunction Hypothyroidism is the most common disorder of thyroid function. It can be divided into patients who have a failure of the thyroid gland to produce sufficient thyroid hormone (primary hypothyroidism) and patients in which pituitary or hypothalamic disease is associated with impaired TSH stimulation (central or secondary hypothyroidism). Worldwide, primary hypothyroidism is caused most often by iodine deficiency. In areas where iodine is sufficient, chronic autoimmune thyroiditis (Hashimoto s thyroiditis) accounts for most cases. Other causes include postpartum thyroiditis, surgical removal, or radioactive iodine ablation of the gland. Hypothyroidism present at birth (cretinism) is the most common preventable cause of mental retardation in the world. 

Inoue etal. (1975) Observational study Japan Higher prevalence of juvenile chronic lymphocytic thyroiditis (Hashimoto s thyroiditis) among schoolchildren from a seaside area compared with an urban area with high iodine intake of seaweed as a potential causative factor... 

The detection of thyroid autoantibodies is important in the diagnosis of chronic lymphocytic thyroiditis (Hashimoto s disease) and the rarer forms of autoimmune thyroid disease, as the earlier reviews showed (D6, H2, 014). There are three antigen-antibody systems to be considered, namely, the two antibodies reacting with thyroid colloid [thyro-globulin and second colloid antigen (CA2), respectively], and in addition the antibody reacting with thyroid microsomes. 

In another recent example, Hashimoto reported photoaffinity experiments on retinoic acid receptors (RAR). Retinoic acid plays a critical role in cell proliferation and differentiation. RARs belong to the superfamily of nuclear/ thyroid hormone receptors. They consist of six transmembrane domains (A-F) which is a general feature of these receptors. The A/B domains have an autonomous transactivation function while the C-domain contains the Zn-finger, which binds to DNA. The large E-domain participates in ligand binding, dimerization, and ligand dependent transactivation. Finally, D- and F-domains help the orientation and stabilization of the E-domain. 

Miyamoto, T, Kaneko, A., Kakizawa, T, Yajima, H., Kamijo, K., Sekine, R., Hiramatsu, K., Nishii, Y, Hashimoto, T. Hashizume, K. (1997) Inhibition of peroxisome proliferator signaling pathways by thyroid hormone receptor. Competitive binding to the response element. J. biol. Chem., Ill, 7752-7758... 

Hypothyroidism, a condition in which the circulating concentrations of thyroid hormones are too low, is the most prevalent thyroid disease. Primary hypothyroidism, the commonest form, is an autoimmune disease (Hashimoto s thyroiditis) often associated with goitre. Like other autoimmune diseases, it is more prevalent in women (4 per 1000) than in men (1 per 1000). Other causes include thyroidectomy, radioac tive ablation and, in some countries, iodine deficiency. Hypothyroidism can also be caused by several drugs, including lithium, interleukin-2 and interferon. Secondary hypothyroidism is a disease caused by decreased secretion of TSH by the pituitary. 

The thyroid gland also regulates its uptake of iodide and thyroid hormone synthesis by intrathyroidal mechanisms that are independent of TSH. These mechanisms are primarily related to the level of iodine in the blood. Large doses of iodine inhibit iodide organification (Wolff-Chaikoff block, see Figure 38-1). In certain disease states (eg, Hashimoto s thyroiditis), this can inhibit thyroid hormone synthesis and result in hypothyroidism. Hyperthyroidism can result from the loss of the Wolff-Chaikoff block in susceptible individuals (eg, multinodular goiter). 

Hashimoto s thyroiditis Autoimmune destruction of thyroid Present early, absent later Mild to severe... 

The most common cause of hypothyroidism in the USA at this time is probably Hashimoto s thyroiditis, an immunologic disorder in genetically predisposed individuals. In this condition, there is evidence of humoral immunity in the presence of antithyroid antibodies and lymphocyte sensitization to thyroid antigens. Certain medications can also cause hypothyroidism (Table 38-5). 

The effectiveness of immunosuppressive drugs in autoimmune disorders varies widely. Nonetheless, with immunosuppressive therapy, remissions can be obtained in many instances of autoimmune hemolytic anemia, idiopathic thrombocytopenic purpura, type 1 diabetes, Hashimoto s thyroiditis, and temporal arteritis. Improvement is also often seen in patients with systemic lupus erythematosus, acute glomerulonephritis, acquired factor VIII inhibitors (antibodies), rheumatoid arthritis, inflammatory myopathy, scleroderma, and certain other autoimmune states. 

Reinhardt W, Luster M, Rudorff KH, Heckmann C, Petrasch S, Lederbogen S, Haase R, Sailer B, Reiners C, Reinwein D, Mann K. Effect of small doses of iodine on thyroid function in patients with Hashimoto s thyroiditis residing in an area of mild iodine deficiency. Eur J Endocrinol 1998 139(l) 23-8. 

Shibata H, Hayakawa H, Hirukawa M, Tadokoro K, Ogata E. Hypersensitivity caused by synthetic thyroid hormones in a hypothyroid patient with Hashimoto s thyroiditis. Arch Intern Med 1986 146(8) 1624-5. 

Watanabe U, Hashimoto E, Hisamitsu T, Obata H, Hayashi N. The risk factor for development of thyroid disease during interferon-alpha therapy for chronic hepatitis C. Am J Gastroenterol 1994 89(3) 399-403. 

Nobuyuki Takasu, Masaki Takara, Ichiro Komiya. Rifampicin induced hypothyroidism in patients with Hashimoto s thyroiditis. N Engl J Med 2005 352(5) 518-9. 

Kifor et al. (2003) found autoantibodies to the CaR in four patients who had a clinical picture resembling that of FHH in the setting of other autoimmune conditions (e.g., Hashimoto s thyroiditis and sprue). The patients sera stimulated PTH secretion and inhibited high calcium-stimulated inositol phosphate accumulation and MAPK activation, presumably owing to antibody-mediated inhibition of the CaR. Further studies of a larger number of patients are required to determine the incidence of autoimmune, PTH-dependent hypocalciuric hypercalcemia in the presence of various types of autoimmunity. 

There are many forms of hypothyroidism, differing in their cause and age of onset (see Table 31-1). Severe adult hypothyroidism (myxedema) may occur idio-pathically or may be caused by specific factors such as autoimmune lymphocytic destruction (Hashimoto disease). In the child, thyroid function may be congenitally impaired, and cretinism will result if this condition is untreated. Hypothyroidism may result at any age if the dietary intake of iodine is extremely low. Several other forms of hypothyroidism that have a genetic or familial basis also exist.54... 

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