Iodine

About: Iodine is a research topic. Over the lifetime, 8936 publications have been published within this topic receiving 139981 citations. The topic is also known as: I & element 53.

Do thyroxine and thyroid-stimulating hormone levels reflect urinary iodine concentrations?

Abstract: The toxicity of environmental chemicals such as nitrates, thiocynates, and perchlorates, some therapeutics, and dietary goitrogens can lower thyroidal iodine uptake and result in hypothyroidism and goiter. Iodine sufficiency, essential for normal thyroid hormone synthesis, is critical during gestation to assure that sufficient thyroxine (T4) and iodine reach the developing fetus. Spot urinary iodide (UI) measurements are used globally to indicate and monitor iodine sufficiency of populations. In individuals, however, UI are not routinely measured; instead, normal serum thyroid-stimulating hormone (TSH) and T4 concentrations serve as surrogate indicators of iodine sufficiency as well as thyroidal health. Our objective was to examine the relationship between UI concentrations and serum T4 and TSH concentrations in individuals in an "iodine-sufficient population." Using a cross-sectional sample of the US population (n = 7628) from the National Health and Nutrition Examination Survey (NHANES III; 1988-1994) database, we examined the relationship among UI, T4, and TSH in pregnant and nonpregnant women and in men (15-44 years). There was a lack of relationship between UI (or UI/Cr) concentrations and serum T4 or TSH concentrations. Therefore, TSH and T4 are not appropriate markers of UI concentrations in this population. Monitoring the status of iodine nutrition of individuals in the United States may be important because serum TSH and T4 concentrations do not indicate low iodine status.

Formation of iodoprotein during the peripheral metabolism of 3,5,3'-triiodo-L-thyronine-125I in the euthyroid man and rat.

Abstract: 3,5,3'-Triiodo-L-thyronine-(125)I (T3-(125)I) metabolism was studied in nine euthyroid human subjects on blocking doses of nonradioactive iodide. After the intravenous injection of T3-(125)I, the fractional disappearance rate of plasma radioactivity progressively disappearance rate of plasma radioactivity progressively decreased with time. Analysis of individual plasma samples by dialysis, electrophoretic, and extraction techniques revealed three radioactive components: T3-(125)I, iodide-(125)I, and an unidentified material which was nonextractable in acid butanol (NE(125)I). Ne(125)I rose to maximal levels 24-36 hr after injection of T3-(125)I and then decreased with a fractional rate which approached, after 12-14 days, approximately 0.05 day(-1) (t(1/2) = 14 days). The plasma T3-(125)I concentration, obtained by subtraction of iodide-(125)I and NE(125)I from the plasma total (125)I, declined at a constant fractional rate with time with a t(1/2) of 1.5 days. Qualitatively similar results were obtained in rats. After 72 hr, 57% of the plasma and 40% of the liver radioactivity was NE(125)I. Chromatographic purification of the T3-(125)I before injection did not alter these results. The extrathyroidal origin of NE(125)I was further demonstrated by similar results in thyroidectomized rats maintained on thyroxine. NE(125)I from human sera separated from the other radioiodinated substances by ion-exchange chromatography was quantitatively precipitated by trichloracetic acid, not dialyzable, insoluble in CHCl(3):CH(2)OH, and migrated with albumin during starch-gel electrophoresis. Based on these properties, NE(125)I was tentatively identified as iodoalbumin. Observations in rats equilibrated with (125)I, as well as nonradioactive iodine determinations in human sera before and after acid butanol extraction, indicate that 10-20% of the serum organic iodine is in the form of iodoprotein. Our studies suggest that this moiety may be derived at least in part from the peripheral metabolism of the thyroid hormones.

Iodine separation procedure for the determination of129I and127I in soil by neutron activation analysis

Abstract: A radiochemical neutron activation analytical method for the determination of129I and127I in soil samples was studied. Iodine was separated from the sample prior to the irradiation by volatilization, i.e. by combustion of the sample and trapping of the iodine in an alkaline solution together with a reducing agent. This method enables one to digest samples containing up to 100 g dry matter. The chemical yield was mostly more than 90%. After irradiation the iodine fraction was further purified by solvent extraction. The detection limit of the129I/127I ratio was 1×10−9.

Pathogenesis of autonomous thyroid nodules: in vitro study of iodine and adenosine 3',5'-monophosphate metabolism

Abstract: The in vitro characteristics of iodide and cAMP metabolism have been compared in tissues from autonomously functioning thyroid nodules and their quiescent counterpart to test the hypothesis that autonomy may result from constitutive activation of the tissue's TSH, cAMP, and protein phosphorylation regulatory axis, as in vivo nodular tissue took up more iodide. This effect was entirely due to increased transport capacity, the affinity of iodide transport, and the fractional binding of iodide to protein remaining unchanged. However, at high concentrations total iodide binding to protein was similar in quiescent and nodular tissue. In both tissues, this metabolic step was enhanced by phorbol esters and the ionophore A23187. As evaluated by autoradiography of two-dimensional gel protein electrophoregrams, no differences in the patterns of protein synthesis or phosphorylation between quiescent and nodular tissue were found. Basal cAMP levels were similar in quiescent and nodular tissue. The cAMP response to TSH was lower in nodular tissue, with no change in sensitivity or kinetics; both tissues responded to forskolin. No systematic suppression of iodide inhibition or abnormal responses to other hormones or neurotransmitters were found. Three proteins (24K-1, 24K-2, and 26K) were phosphorylated only in the presence of TSH or forskolin in both quiescent and nodular tissue. One protein substrate (20K) was phosphorylated in the presence of TSH in the quiescent, but not in the nodular, tissue. In conclusion, 1) slices from autonomous thyroid nodules reproduce the in vivo characteristics of the lesion and are, therefore, a suitable in vitro experimental model for biochemical studies; 2) taken together with data from transplantation experiments, the reproduction in vitro or its in vivo characteristics suggest an inherent defect in the nodule; 3) the homogeneity of biochemical findings within each nodule is compatible with the clonality of the lesion; 4) the autonomous nodule is a minimal deviation tumor; and 5) the characteristics of the TSH, cAMP, protein phosphorylation cascade are qualitatively normal, and autonomy does not result from constitutive activation of this system; and 6) a 20K protein, not phosphorylated in response to TSH in the nodule, could represent an absent negative controlling element.