Thyroglobulin

Thyroglobulin (Tg) is a 660 kDa, dimeric protein produced by the follicular cells of the thyroid and used entirely within the thyroid gland. Thyroglobulin protein accounts for approximately half of the protein content of the thyroid gland.

Each thyroglobulin molecule contains approximately 100-120 tyrosyl (Tyrosine) residues. However, because only a small number (>20) of these tyrosine residues are subject to iodination by thyroperoxidase in the follicular colloid, each Tg molecule is only able to form very small amounts of thyroid hormone (5-6 molecules of either T4 and T3).

Function

Tg is used by the thyroid gland to produce the thyroid hormones thyroxine (T4) and triiodothyronine (T3). The active form of triiodothyronine, 3, 5, 3' triiodothyronine, is produced both within the thyroid gland and in the periphery by 5'-deiodinase (which has been referred to as tetraiodothyronine 5' deiodinase). It is presumed that Tg and thyroid are also an important storage of iodine for all body needs, in particular, for many iodine-concentrating organs such as breast, stomach, salivary glands, thymus, choroid plexus and cerebrospinal fluid, etc. (see iodine in biology).

Hashimoto's thyroiditis

Hashimoto's thyroiditis or chronic lymphocytic thyroiditis is an autoimmune disease in which the thyroid gland is attacked by a variety of cell- and antibody-mediated immune processes, causing primary hypothyroidism. It was the first disease to be recognized as an autoimmune disease. It was first described by the Japanese specialist Hakaru Hashimoto in a paper published in Germany in 1912.

Signs and symptoms

There are many symptoms that are attributed to Hashimoto's thyroiditis or Hashimoto's disease. The most common symptoms include the following: fatigue, weight gain, pale or puffy face, feeling cold, joint and muscle pain, constipation, dry and thinning hair, heavy menstrual flow or irregular periods, depression, panic disorder, a slowed heart rate, and problems getting pregnant and maintaining pregnancy.

Hashimoto’s disease is about seven times more common in women than in men. It can occur in teens and young women, but more commonly shows up in middle age, particularly for men. People who develop Hashimoto’s disease often have family members who have thyroid or other autoimmune diseases, and sometimes have other autoimmune diseases themselves.

Autoimmune disease

Autoimmune diseases arise from an abnormal immune response of the body against substances and tissues normally present in the body (autoimmunity). This may be restricted to certain organs (e.g. in autoimmune thyroiditis) or involve a particular tissue in different places (e.g. Goodpasture's disease which may affect the basement membrane in both the lung and the kidney).

The treatment of autoimmune diseases is typically with immunosuppression—medication that decreases the immune response.

A large number of autoimmune diseases are recognized. A major understanding of the underlying pathophysiology of autoimmune diseases has been the application of genome wide association scans that have identified a striking degree of genetic sharing among the autoimmune diseases.

Definition

For a disease to be regarded as an autoimmune disease it needs to answer to Witebsky's postulates (first formulated by Ernst Witebsky and colleagues in 1957 and modified in 1994):