Thyroid Thyroxine, Triiodothyronine

Thyroid-stimulating hormone (TSH) Thyrotropin-releasing hormone (TRH)(+) Thyroid Thyroxine, triiodothyronine... 

Thyroid effect. Goffee oil, administered orally to 11 healthy normolipemic volunteers at a dose of 2 g/day for 3 weeks, produced no effect on serum total and free thyroxine, triiodothyronine, and thyroid-stimulating hormone... 

The normal thyroid gland secretes sufficient amounts of the thyroid hormones—triiodothyronine (T3) and tetraiodothyronine (T4, thyroxine)—to normalize growth and development, body temperature, and energy levels. These hormones contain 59% and 65% (respectively) of iodine as an essential part of the molecule. Calcitonin, the second type of thyroid hormone, is important in the regulation of calcium metabolism and is discussed in Chapter 42. 

Three types of iodothyronine deiodinase remove iodine atoms from thyroxine to form the active thyroid hormone triiodothyronine and also to inactivate the hormone by removing additional iodine531 541-546 (see also Chapter 25). In this case the - CH2- Se- may attach the iodine atom, removing it as I+ to form -CH2-Se-I. The process could be assisted by the phenolic -OH group if it were first tautomerized (Eq. 15-60). 

Eukaryote organisms primarily respond to external signals by an initial signal perception by receptors. In general, such receptors can be either cytosolic or located on the plasma membrane [13-15]. The former mechanism applies to thyroid hormones (triiodothyronine and tetraiodothyronine or thyroxine), retinoids (e.g. retinoic acid), the insect developmental hormones such as ecdysone, steroid hormones (such as... 

Thyroid Thyroxine (T4], Triiodothyronine (T3] Increase cellular metabolism facilitate normal growth and development... 

FIGURE 31-1 Structure of the thyroid hormones triiodothyronine (T3] and thyroxine (T4X Addition of one iodine atom [I] to tyrosine produces monoiodotyrosine addition of a second iodine atom produces diiodotyrosine. A monoiodotyrosine and diiodotyrosine combine to form triiodothyronine (T3X Coupling of two diiodotyrosines forms thyroxine (T4X... 

Thyroxine, triiodothyronine (iodine- Thyroid Various tissues responses in lymphatic system Regulate metabolism required for... 

Q3 Make a summary of the actions of the thyroid hormones triiodothyronine (T3) and thyroxine (T4)... 

Hyperthyroidism is associated with an increase in the levels of thyroid hormone, triiodothyronine (T3) and thyroxin (T4), in the body, which in turn raises the metabolic rate of all tissues. 

Thyroid-stimulating hormone (TSH) that regulates the growth of the thyroid gland and the iodination of amino acids to produce the thyroid hormones triiodothyronine and thyroxine (see Chapter 52)d... 

Iodine is an essential element with an important role in mammals in the regulation of metabolism, through the action of the two related hormones produced by the thyroid gland, triiodothyronine (T3) and thyroxine (T4). Iodine, which is relatively scarce, is actively concentrated in the thyroid gland where both T3 and T4 are produced. 

Iodine is an essential element in humans and other mammals, which is used for the synthesis of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). These hormones play a prominent role in the metabolism of most cells of the organism and in the process of early growth and development of most organs, especially brain (Anderson et al., 2000). Besides T3 and T4, reverse T3 (rT3), monoiodotyrosine (MIT), and diiodotyrosine (DIT) are also synthesized and distributed in the body of humans and animals, but only T3 and T4 have a biological function. Iodine in the human body mainly comes through dietary and water intake, and inhalation of atmospheric iodine. Due to low concentrations of iodine in the air (10—20ng/m ), food and water intake form the major source of iodine for adults, while for infants it is milk. The concentration of iodine in foodstuffs is directly related to that in the environment where the foods come from. Iodine deficiency disorders are mainly found in places where the concentration of iodine in the soil and drinking water is very low. In the water, foodsmffs, and... 

Iodine is essential for the synthesis of the thyroid hormones — triiodothyronine (T3) and thyroxine (T4). An iodine-deficient diet results directly in decreased production of thyroid hormones, which adversely affects not only brain development, but also its functions such as attention, learning and memory. In areas with iodine deficiency, besides the occurrence of more frequent thyroid nodules, the intelligence quotient (IQ) of children is much lower than that in areas with adequate iodine. 

Oral administration of thyroxine (T4) is the treatment of choice for all forms of hypothyroidism. Other thyroid hormone preparations, including desiccated thyroid and triiodothyronine (T3) alone, should not be used for treatment of patients with hypothyroidism (Levy, 1991). The absorption of T3 is very rapid, and high serum levels of T3 are reached rapidly. Furthermore, elderly persons are very sensitive to the effects of T3. A recent meta-analysis of controlled clinical trials has shown that there is no benefit of combined T3 and T4 therapy when compared with T4 therapy alone (Grozinsky-Glasberg et at, 2006). 

Description. Iodine, a nonmetallic trace element, is required by humans for the synthesis of thyroid hormones, triiodothyronine (Tj) and thyroxine (T4). Iodine deficiency is an important health problem throughout much of the world. Most of the Earth s iodine is found in its oceans. In general, the older an exposed soil surface, the more likely the iodine has been leached away by erosion. Mountainous regions, such as the Himalayas, the Andes, and the Alps, and flooded river valleys, such as the Ganges, are among the most severely iodine-deficient areas in the world. ° ... 

Iodine speciation has been successfully carried out using capillary electrophoresis coupled to inductively coupled plasma mass spectrometry. The status of iodine species (such as thyroxine, triiodothyronine or iodide) in serum or urine can give information about the malfunction of the thyroid gland and can explain other metabolic abnormalities. Chromium speciation is not normally required in biological samples because the body converts all of the Cr + to Cr + and so the measurement of total chromium in blood and urine is referred to when in fact Cr + has been determined. Chromium speciation has been carried out in bacteria culture medium, which has used to convert Cr + to Cr ". ... 

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