Thyroid hormone binding ratio

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Thyroid hormone binding ratio
Purposemeasures the "uptake" of T3 or T4

Thyroid hormone binding ratio (THBR) is a Thyroid Function Test that measures the "uptake" of T3 or T4 tracer by Thyroid Binding Globulin (TBG) in a given serum sample. This provides an indirect and reciprocal estimate of the available binding sites on TBG within the sample.

Contents

The results are then reported as a ratio to normal serum.

Indications

Attempts to correct for changes in thyroid binding globulin due to liver disease, protein losing states, pregnancy or various drugs

Previously used to calculate free thyroxine index (total T4 x T3 uptake), an estimate of free T4 (now free T4 is ordered directly.)

Examples

Other Conditions

Limitations

Invalid if other proteins or immunoglobulins compete with TBG, including Familial Dysalbuminemic Hyperthyroxinemia [1]

Related Research Articles

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Serum protein electrophoresis

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Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which stimulates the metabolism of almost every tissue in the body. It is a glycoprotein hormone produced by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid. In 1916, Bennett M. Allen and Philip E. Smith found that the pituitary contained a thyrotropic substance.

Thyroxine-binding globulin mammalian protein found in Homo sapiens

Thyroxine-binding globulin (TBG) is a globulin protein that in humans is encoded by the SERPINA7 gene. TBG binds thyroid hormones in circulation. It is one of three transport proteins (along with transthyretin and serum albumin) responsible for carrying the thyroid hormones thyroxine (T4) and triiodothyronine (T3) in the bloodstream. Of these three proteins, TBG has the highest affinity for T4 and T3 but is present in the lowest concentration. Despite its low concentration, TBG carries the majority of T4 in the blood plasma. Due to the very low concentration of T4 and T3 in the blood, TBG is rarely more than 25% saturated with its ligand. Unlike transthyretin and albumin, TBG has a single binding site for T4/T3. TBG is synthesized primarily in the liver as a 54-kDa protein. In terms of genomics, TBG is a serpin; however, it has no inhibitory function like many other members of this class of proteins.

Triiodothyronine chemical compound

Triiodothyronine, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate.

Transcortin mammalian protein found in Homo sapiens

Transcortin, also known as corticosteroid-binding globulin (CBG) or serpin A6, is a protein produced in the liver in animals. In humans it is encoded by the SERPINA6 gene. It is an alpha-globulin.

Levothyroxine chemical compound

Levothyroxine, also known as L-thyroxine, is a manufactured form of the thyroid hormone thyroxine (T4). It is used to treat thyroid hormone deficiency, including the severe form known as myxedema coma. It may also be used to treat and prevent certain types of thyroid tumors. It is not indicated for weight loss. Levothyroxine is taken by mouth or given by injection into a vein. Maximum effect from a specific dose can take up to six weeks to occur.

Sex hormone-binding globulin mammalian protein found in Homo sapiens

Sex hormone-binding globulin (SHBG) or sex steroid-binding globulin (SSBG) is a glycoprotein that binds to androgens and estrogens. Other steroid hormones such as progesterone, cortisol, and other corticosteroids are bound by transcortin. SHBG is found in all vertebrates apart from birds.

Propylthiouracil chemical compound

Propylthiouracil (PTU) is a medication used to treat hyperthyroidism. This includes hyperthyroidism due to Graves' disease and toxic multinodular goiter. In a thyrotoxic crisis it is generally more effective than methimazole. Otherwise it is typically only used when methimazole, surgery, and radioactive iodine is not possible. It is taken by mouth.

Thyroid disease type of endocrine disease

Thyroid disease is a medical condition that affects the function of the thyroid gland. The thyroid gland is located at the front of the neck and produces thyroid hormones that travel through the blood to help regulate many other organs, meaning that it is an endocrine organ. These hormones normally act in the body to regulate energy use, infant development, and childhood development.

Thyroid storm is a rare but severe and potentially life-threatening complication of hyperthyroidism. It is characterized by a high fever, fast and often irregular heart beat, elevated blood pressure, vomiting, diarrhea, and agitation. Hypertension with a wide pulse pressure occurs in early to mid crisis, with hypotension accompanying shock occurring in the late stage. Heart failure and heart attack may occur. Death may occur despite treatment. Most episodes occur either in those with known hyperthyroidism whose treatment has been stopped or become ineffective, or in those with untreated mild hyperthyroidism who have developed an intercurrent illness.

Hypoalbuminemia medical sign in which the level of albumin in the blood is abnormally low

Hypoalbuminemia is a medical sign in which the level of albumin in the blood is low. This can be due to decreased production in the liver, increased loss in the gastrointestinal tract or kidneys, increased use in the body, or abnormal distribution between body compartments. Patients often present with hypoalbuminemia as a result of another disease process such as sepsis, cirrhosis in the liver, nephrotic syndrome in the kidneys, or protein-losing enteropathy in the gastrointestinal tract. One of the roles of albumin is being the major driver of oncotic pressure in the bloodstream and the body. Thus, hypoalbuminemia leads to abnormal distributions of fluids within the body and its compartments. As a result, associated symptoms include edema in the lower legs, ascites in the abdomen, and effusions around internal organs. Laboratory tests aimed at assessing liver function diagnose hypoalbuminemia. Once identified, it is a poor prognostic indicator for patients with a variety of different diseases. Yet, it is only treated in very specific indications in patients with cirrhosis and nephrotic syndrome. Treatment instead focuses on the underlying cause of the hypoalbuminemia. Albumin is an acute negative phase respondent and NOT a reliable indicator of nutrition status

Liothyronine chemical compound, salt of a drug

Liothyronine is a manufactured form of the thyroid hormone triiodothyronine (T3). It is most commonly used to treat hypothyroidism and myxedema coma. It is generally less preferred than levothyroxine. It can be taken by mouth or by injection into a vein.

Thyroid function tests (TFTs) is a collective term for blood tests used to check the function of the thyroid.

Albumin Family of globular proteins

Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins are commonly found in blood plasma and differ from other blood proteins in that they are not glycosylated. Substances containing albumins, such as egg white, are called albuminoids.

clinically euthyroid patients do not have elevated thyroid-stimulating hormone (TSH) levels. Pathogenesis is unknown but may include decreased peripheral conversion of T4 to T3, decreased clearance of rT3 generated from T4, and decreased binding of thyroid hormones to thyroxine-binding globulin (TBG).

Hypothalamic–pituitary–thyroid axis part of the neuroendocrine system responsible for the regulation of metabolism.

The hypothalamic–pituitary–thyroid axis is part of the neuroendocrine system responsible for the regulation of metabolism and also responds to stress.

Euthyroid sick syndrome (ESS) is a state of adaptation or dysregulation of thyrotropic feedback control wherein the levels of T3 and/or T4 are abnormal, but the thyroid gland does not appear to be dysfunctional. This condition may result from allostatic responses of hypothalamsus-pituitary-thyroid feedback control, dyshomeostatic disorders, drug interferences and impaired assay characteristics in critical illness.

Thyroid hormones hormones produced by the thyroid gland

Thyroid hormones are two hormones produced and released by the thyroid gland, namely triiodothyronine (T3) and thyroxine (T4). They are tyrosine-based hormones that are primarily responsible for regulation of metabolism. T3 and T4 are partially composed of iodine. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3. In humans, the ratio of T4 to T3 released into the blood is approximately 14:1. T4 is converted to the active T3 (three to four times more potent than T4) within cells by deiodinases (5′-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (T1a) and thyronamine (T0a). All three isoforms of the deiodinases are selenium-containing enzymes, thus dietary selenium is essential for T3 production.

The liver plays the major role in producing proteins that are secreted into the blood, including major plasma proteins, factors in hemostasis and fibrinolysis, carrier proteins, hormones, prohormones and apolipoprotein:

References

  1. "T3 or T4 uptake". Pathology outlines. Retrieved 2016-02-25.