What is MIT and DIT?
Through a reaction with the enzyme thyroperoxidase, iodine is bound to tyrosine residues in the thyroglobulin molecules to form monoiodotyrosine (MIT) and diiodotyrosine (DIT). Linking two moieties of DIT produces T4.
What is the function of T3 and T4?
The thyroid gland releases triiodothyronine (T3) and thyroxine (T4). These hormones play an important role in regulation of your weight, energy levels, internal temperature, skin, hair, nail growth, and more.
What is the function of thyroxine?
Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland. It plays vital roles in digestion, heart and muscle function, brain development and maintenance of bones.
What causes overactive thyroids?
Hyperthyroidism (overactive thyroid) occurs when your thyroid gland produces too much of the hormone thyroxine. Hyperthyroidism can accelerate your body’s metabolism, causing unintentional weight loss and a rapid or irregular heartbeat.
What is the cretinism?
Cretinism refers to severe hypothyroidism in an infant or child. This is classically the result of maternal iodine deficiency, and thankfully is increasingly rare.
What is the significance of the slight swelling called a goiter?
A goiter can occur in a gland that is producing too much hormone (hyperthyroidism), too little hormone (hypothyroidism), or the correct amount of hormone (euthyroidism). A goiter indicates there is a condition present which is causing the thyroid to grow abnormally.
How does T4 convert to T3?
T4 is converted into T3, the active form of thyroid hormone, by two enzymes called deiodinases. People with hypothyroidism are treated with a synthetic T4 hormone, which the enzymes convert to T3. This treatment is usually effective, but some people continue to have symptoms even after treatment.
What happens cretinism?
Congenital hypothyroidism, previously known as cretinism, is a severe deficiency of thyroid hormone in newborns. It causes impaired neurological function, stunted growth, and physical deformities.
What does cretinism mean?
All rights reserved. Acretin, from the French chrétien (Christian), is defined in Webster’s Encyclopedic Unabridged Dictionary (1) as “one who is human despite deformities”. The medical definition of cretinism is untreated congenital hypothyroidism, with or without a goiter.
What is thyroxine made from?
Thyroxine hormone is produced in the thyroid gland from tyrosine and iodine. Thyrotropin-releasing hormone (TRH) is produced by the hypothalamus. It stimulates the production of thyroid-stimulating hormone (TSH) in the anterior pituitary gland, which affects the thyroid-stimulating hormone receptor (TSHR).
What is the meaning thyroxine?
(thy-ROK-seen) A hormone that is made by the thyroid gland and contains iodine. Thyroxine increases the rate of chemical reactions in cells and helps control growth and development. Thyroxine can also be made in the laboratory and is used to treat thyroid disorders.
How is iodotyrosine made from tyrosine?
Iodotyrosine is made from tyrosine via thyroid peroxidase and then further iodinated by this enzyme to make the di-iodo and tri-iodo variants. Two molecules of di-iodotyrosine combine to form T4, and one molecule of mono-iodotyrosine combines with one molecule of di-iodotyrosine to form T3.
What is the major abnormality in the pathophysiology of iodotyrosine deficiency?
The major abnormality is an impairment of both intrathyroidal and peripheral deiodination of iodotyrosines, presumably because of the dysfunction of the iodotyrosine DEHAL1B gene (see discussion regarding iodide metabolism in Chapter 11 ). 153,154
How do you catalyze iodothyronine oxidation?
Iodide oxidation and binding to thyroglobulin and iodotyrosine coupling in iodothyronines are catalyzed by the same enzyme, thyroperoxidase, with H 2 O 2 used as a substrate. 154 The same regulations therefore apply to the two steps.
Is iodination required for iodotyrosine coupling?
Iodotyrosine coupling to iodotyrosines is catalyzed by the same system and is therefore subject to the same regulations as iodination. However, coupling requires that suitable tyrosyl groups in thyroglobulin be iodinated, that is, that the level of iodination of the protein be sufficient.