Excess iodine

An aqueous 1 % starch (amylose) spray can be sprayed on later to intensify the color contrast between the chromatogram zones and the layer background the well known blue-colored iodine starch inclusion complexes are formed. This later treatment with starch solution should only be carried out when the iodine excess has evaporated from the layer background so that only traces of iodine remain in the chromatogram zones. Otherwise the whole chromatogram will be colored dark blue (test at a corner of the chromatogram ). 

Iodine excess (including radiocontrast, amiodarone) Thyrotoxicosis without hyperthyroidism Subacute thyroiditis Silent (painless) thyroiditis... 

Amiodarone may induce thyrotoxicosis (2% to 3% of patients) or hypothyroidism. It interferes with type I 5 -deiodinase, leading to reduced conversion of T4 to T3, and iodide release from the drug may contribute to iodine excess. Amiodarone also causes a destructive thyroiditis with loss of thyroglobulin and thyroid hormones. 

Regiospecific hydrocyanation of alkenes. Reaction of /-butyl isocyanide with the adducts of 1 with alkenes results in products (2) that are converted by iodine (excess) into hydrocyanides (3) and /-butyl iodide with release of ClCp2ZrI. (CH1).,SiN=C can be used in place of (CH,)3CN=C, but yields are generally lower.2... 

Pitsiavas V, Semerdely P, Li M, Boyages SC (1997) Amiodarone induces a different pattern of ultrastructural change in the thyroid to iodine excess alone in both BBAV rat and the Wislar rat. Eur J Endocrinol 137 89-98... 

Sleight SD, Mangkoewidjojo S, Akoso BT, et al. 1978. Polybrominated biphenyl toxicosis in rats fed an iodine-deficient, iodine-adequate, or iodine-excess diet. Environ Health Perspect 23 341-346. 

Because of reports of severe hyperthyroidism after the introduction of iodized salt in two severely iodine-deficient African counties (Zimbabwe and the Democratic Republic of the Congo), a multicenter study has been conducted in seven countries in the region to evaluate whether the occurrence of iodine-induced hyperthyroidism after the introduction of iodized salt was a generalized phenomenon or corresponded to specific local circumstances in the two affected countries (46). Iodine deficiency had been successfully eliminated in all of the areas investigated and the prevalence of goiter had fallen markedly. However, it was clear that some areas were now exposed to iodine excess as a result of poor monitoring of the quality of iodized salt and of the iodine intake of the population. In these areas, iodine-induced hyperthyroidism occurred only when iodized salt had been recently introduced. 

Minelli R, Braverman LE, Valli MA, Schianchi C, Pedrazzoni M, Fiaccadori F, Salvi M, Magotti MG, Roti E. Recombinant interferon alpha (rIFN-alpha) does not potentiate the effect of iodine excess on the development of thyroid abnormalities in patients with HCV chronic active hepatitis. Clin Endocrinol (Oxf) 1999 50(1) 95-100. 

In the adulL hypothyroidism may rarely be caused by iodine deficiency and goitrogens. Rarely, iodine ingestion in the form of expectorants can lead to hypothyroidism. In sensitive persons, the iodide blocks the synthesis of thyroid hormone, leading to an increased secretion of TSH, which causes thyroid enlargement. Thus both iodine excess and iodine deficiency can cause decreased secretion of thyroid hormone. 

Deficiency of iodine, a component of thyroid hormones, may result in goiter formation (see Chap. 73). However, not everyone with an iodine-deficient diet will develop a goiter. Thyroxine (T4) and triiodothyronine (T3) can be used to assess iodine status (see Table 135-8). Intravenous iodine supplements typically are not necessary except during long-term parenteral nutrition with minimal enteral intake. Iodine needs generally are met by cutaneous absorption of iodine from germicides (e.g., povidone-iodine) used in catheter care or consumption of iodized salt. " Use of povidone-iodine wiU likely decrease with the increased use of chlorhexidine for catheter care, and the need for iodine supplementation must be individualized. Iodine excess is rarely a clinical concern when thyroid function is normal. 

In this respect, the suggested maximum tolerable dietary levels of iodine for common livestock in the European Union is lOmgkg feed DM. For solipeds (horses, etc.), the highest tolerable iodine concentration has been limited to 4 mg kg feed DM. Horses are considerably less tolerant to iodine excess (5 mg kg feed DM) than cattle, sheep, and poultry (NRG 1980, Hetzel and Maberly 1986, McDowell 1992). Supplementation in the amounts stated above is dangerous for the reproductive performance. An influence on the growth of chicken embryos and brain development has also been reported (Travnicek et al. 1997). 

Koutras da, Moulopoulou DS, Marafelia P, PiPERiNGOs GD, Karaiskos KS et al. (1999) The optimum iodine intake and the undesirable effects of iodine excess. In Bauch K-H ed. 2. Symposium, interdisziplinare Probleme des lodmangels, der lodprophylaxe, des lodexzesses und antithyreoidaler Substanzen, pp. 140—143. Berlin Chemie, Berlin, Germany. 

An increase in thyroid weight and incidence of colloid goiter are useful in the diagnosis of iodine excess. The finding of goitrous foals from mares consuming a highly iodized feed (Baker and Lindsey, 1968) is justifiably a frequently cited example of iodine excess in domestic animals. 

Thyroxine is critical for the developing human brain and it is likely to be compromised whether serum T4 levels are reduced through transient hypothyroxinemia, with a contribution from iodine deficiency, or from transient hypothyroidism caused by iodine excess. 

Iodine deficiency during the perinatal period and exposure to an iodine excess is quite conspicuos. The iodine intake of newborns is entirely dependent on the iodine content of breast milk and formula preparations used to feed them. The minimum recommended dietary allowance (RDA) for different age groups is summarized in Table 50.1. To meet such requirements, the iodine content of formulas for premature newborns should contain 20 j,g/dl, and that of first and follow-up preparations 10 j,g/dl. We refer here to these new... 

There are several causes for exposure to an iodine excess, caused by iodine-containing antiseptics (10000 pg of iodine/ ml) and radiologic contrast media (250-370 mg of iodine/ ml).The aim is to bring to attention the evidence that even a minor iodine overload may impair thyroid function during a period of development when thyroid hormones are very important for the brain (Ares et aL, 1995, 2007). The precocious diagnosis and treatment of changes in thyroid function associated with iodine excess could have beneficial effects in the prevention of developmental abnormalities. We surest a protocol to evaluate thyroid function when iodine... 

Figure 50.3 Mean total T4 (a) and T3 (b) serum concentration in preterm babies related to low or high iodine urinary excretion. Effect of iodine excess in the neonatal period.

Tabie 50.9 Percentage of normal thyroid function and incidence of hypothyroidism in newborns with iodine excess due to angiocardiography in the neonatal period... 

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