Thyroid Metabolism

They may interfere with thyroid metabolism and have effects on neurological development (RCEP, 2003, p2 Covaci et al, 2006 Langley, 2004). These effects should not be weighed against the deaths and damage caused by fires, because those affected can do almost nothing to reduce them. 

Thyroid disorders. Disturbances in thyroid metabolism can occur at any level of the hypothalams-pituitary-thyroid-peripheral tissue axis. Several of these disorders have been discussed previously. Hyperthyroidism is more prevalent in women than men. The three most common causes of hyperthyroidism are Graves hyperthyroidism, toxic multinodular goiter, and toxic adenoma. The clinical features of hyperthyroidism include hyperkinesis, weight loss, cardiac anomalies (e.g., atrial fibrillation), fatigue, weakness, sweating, palpitations, and nervousness. The typical biochemical laboratory parameters are increased serum free T4 and decreased serum TSH. 

Studies of complexes of iodine with imidazoles have demonstrated that the 1 1 charge transfer complexes are of the n-a type with donation of the electron pair from N-3. Formation constants determined for the complexes with 1-methylimidazole, methimazole, and clotrimazole indicate strong donor-receptor interaction, implying an expected effect on thyroid metabolism of these imidazoles <83BSB923, 86H(24)1955>. 

It had been reported earlier (Uthus and Nielsen 1990, Nielsen 1991) that vanadium-deficient nutrition of rats led to increased thyroid weights and thyroid bo-dyweight ratios, and decreased growth. These studies showed that stress factors which alter thyroid status or iodine metabolism also enhance the response to vanadium deprivation. Indeed, it is possible that vanadium is essential in the control not only of certain enzyme reactions but also thyroid metabolism. 

It has also been mentioned that salt iodization efficacy, the preferred strategy for IDD, might be influenced by ID, because this disorder impairs thyroid metabolism (WHO, 2001, Zimmermann et al., 2000). It has been observed that two initial steps in thyroid hormone synthesis are catalyzed by Fe-dependent thyroid peroxidase (TPO). One Fe-defl-ciency anemia study in rats showed reduced TPO activity, and decreased plasma T4 and triiodothyronine (T3) levels (Hess et al, 2002). IDA may also alter the central nervous systems thyroid metabolism control, and reduce T4 to T3 peripheral conversion (Beard etal, 1998), modify nuclear T3 binding (Smith et al, 1994), and increase circulating thyrotropin (TSH) (Beard et at, 1990). The therapeutic response to oral iodized oil is impaired in children with IDA compared with Fe-sufficient children (Zimmermann et al, 2000). 

Zimmermann et al. (2002) remind us that, in less industrialized countries, children are at high risk for both goiter and anemia, and that ID adversely effects thyroid metabolism, reducing the efficacy of iodine prophylaxis in areas... 

It has been shown that Se, in addition to I, is directly related to thyroid hormone metabolism because the deiodi-nases (I, II, and III types) contain Se. Zn, Ca and Mg, are also involved in thyroid metabolism (Arthur, 1991 Simsek... 

An altered thyroid metabolism may play an important role in the complex pathophysiology of HF progression arising... 

Some hereditary diseases affecting thyroid metabolism manifest themselves only at a later age. Two examples will be given. 

Marracdni P. Prevalence of thyroid dysfunction and effect of contrast medium on thyroid metabolism in cardiac patients undergoing coronary angiography. Acta Radiol 2013 54(l) 42-7. 

Izumi M, Larsen PR. 1978. Correlation of sequential changes in serum thyroglobulin, triiodothyronine and thyroxine in patients with Graves disease and subacute thyroiditis. Metabolism, 27, 449-460. 

Effect of graded doses of iodide administered 30 min before killing on the thyroidal metabolism of iodine in rats. Values shown are mean SE (in brackets) of values obtained in 5 rats. For purposes of reference, the curve of total organic iodinations is shown as a dotted line in the lower 3 panels ( ). 

The demonstration that 5 D-I, like glutathione peroxidase, is a selenoenzyme has led to the recognition of a key role for selenium in thyroid hormone metabolism. In male rats, selenium deficiency results in decreased 5 D-I activity, increased serum T4 concentrations and little change in serum T3, rTs and TSH concentrations. In selenium-deficient pregnant rats, in contrast to what is observed in selenium-deficient male rats, maternal serum T4 concentrations are normal and serum rTs concentations are markedly increased, suggesting that the influence of selenium-deficiency on the thyroid metabolism of the mother and the fetus might be different than in the adult rat. 

Role of Iodine in Thyroid Metabolism. Turnover of Diiodotyrosine and... 

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