#Hypothyroidism up to date free

Many patients also have antibodies that block the action of TSH on the TSH receptor or that are cytotoxic to thyroid cells. These antibodies have little, if any, functional activity. In addition, more than 90 percent of patients with chronic autoimmune thyroiditis have high serum concentrations of autoantibodies to thyroglobulin, thyroid peroxidase (thyroid microsomal antigen), or the thyroid sodium-iodide transporter ( table 2).

Cytotoxic T cells may directly destroy thyroid cells. They differ in the extent of lymphocytic infiltration, fibrosis, and thyroid follicular cell hyperplasia of the thyroid gland but not in their pathophysiology.īoth cellular and humoral factors may contribute to the thyroid injury and hypothyroidism in chronic autoimmune thyroiditis. The disorder has two forms: goitrous and atrophic. (See 'Clinical manifestations of hypothyroidism'.)Īll of the thyroid disorders considered below can cause either subclinical or overt hypothyroidism.Ĭhronic autoimmune (Hashimoto's) thyroiditis - The most common cause of hypothyroidism in iodine-sufficient areas of the world is chronic autoimmune (Hashimoto's) thyroiditis, which is caused by cell- and antibody-mediated destruction of thyroid tissue.

Most of these patients have symptoms and signs of hypothyroidism.

#Hypothyroidism up to date free

Overt hypothyroidism – Overt hypothyroidism is defined as a high serum TSH concentration in the presence of a low serum free T4 concentration.(See 'Subclinical hypothyroidism in nonpregnant adults'.) These patients have few, if any, symptoms and signs of hypothyroidism. This combination of findings reflects the great sensitivity of TSH secretion to very small reductions in thyroid secretion. Subclinical hypothyroidism – Subclinical hypothyroidism is defined as a high serum TSH concentration in the presence of normal serum free T4 and T3 concentrations.We recognize two degrees of primary hypothyroidism: Thus, the combination of a low serum T4 and a high serum TSH concentration both confirms the diagnosis of hypothyroidism and indicates that it is due to primary thyroid disease. PRIMARY HYPOTHYROIDISM - In patients with hypothyroidism caused by disease of the thyroid gland, decreased secretion of thyroxine (T4) and triiodothyronine (T3) leads to a reduction in the serum concentrations of the two hormones, which results in a compensatory increase in TSH secretion. (See 'Diagnosis of and screening for hypothyroidism in nonpregnant adults' and 'Treatment of primary hypothyroidism in adults'.) The diagnostic approach to and treatment of hypothyroidism are discussed separately. This topic will review the major causes of hypothyroidism. The cause can often be identified, or at least strongly inferred, from the history and physical examination. It may be the first or only manifestation of hypothalamic or pituitary disease.It may be caused by a drug, such as lithium or an iodine-containing drug, and disappear when the drug is discontinued.Hypothyroidism may be transient and require no or only short-term therapy, as in patients with painless thyroiditis or postpartum thyroiditis.The cause of hypothyroidism should be identified in every patient for the following reasons: Much less often it is caused by decreased secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary gland or by decreased secretion of thyrotropin-releasing hormone (TRH) from the hypothalamus ( table 1). In the vast majority of cases, it is caused by thyroid disease (primary hypothyroidism). INTRODUCTION - Hypothyroidism can result from a defect anywhere in the hypothalamic-pituitary-thyroid axis.