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.

The effect of small increases in dietary iodine on thyroid function in euthyroid subjects.

Abstract: Dietary iodine intake in the United States is greater than that considered necessary for the maintenance of normal thyroid function. The administration of pharmacologic quantities of iodine (10 to 1,000 mg daily) to euthyroid subjects results in small decreases in the serum T4 and T3 concentrations and a compensatory increase in the basal and TRH-stimulated serum TSH concentrations. Studies were carried out to determine whether a far smaller increase in iodine intake would also affect thyroid function. Normal volunteers received 1,500, 500, or 250 micrograms supplemental iodine daily for 14 days. Following the administration of 1500 micrograms iodine daily, there were small but significant decreases in the serum T4 and T3 concentrations and a small compensatory increase in the serum TSH concentration and the serum TSH response to TRH. In contrast, no changes in pituitary-thyroid function occurred during the administration of 500 or 250 micrograms iodine daily. These findings indicate that a small increase in dietary iodine can induce subtle changes (all values remaining within the normal range) in pituitary-thyroid function, probably by inhibiting thyroid hormone release. The smaller iodine supplements of 500 and 250 micrograms daily, quantities that may easily be achieved under normal conditions, did not, however, affect thyroid function.

Isolation of Iodide-Oxidizing Bacteria from Iodide-Rich Natural Gas Brines and Seawaters

Abstract: Iodide-oxidizing bacteria (IOB), which oxidize iodide (I-) to molecular iodine (I2), were isolated from iodide-rich (63 microM to 1.2 mM) natural gas brine waters collected from several locations. Agar media containing iodide and starch were prepared, and brine waters were spread directly on the media. The IOB, which appeared as purple colonies, were obtained from 28 of the 44 brine waters. The population sizes of IOB in the brines were 10(2) to 10(5) colony-forming units (CFU) mL(-1). However, IOB were not detected in natural seawaters and terrestrial soils (fewer than 10 CFU mL(-1) and 10(2) CFU g wet weight of soils(-1), respectively). Interestingly, after the enrichment with 1 mM iodide, IOB were found in 6 of the 8 seawaters with population sizes of 10(3) to 10(5) CFU mL(-1). 16S rDNA sequencing and phylogenetic analyses showed that the IOB strains are divided into two groups within the alpha-subclass of the Proteobacteria. One of the groups was phylogenetically most closely related to Roseovarius tolerans with sequence similarities between 94% and 98%. The other group was most closely related to Rhodothalassium salexigens, although the sequence similarities were relatively low (89% to 91%). The iodide-oxidizing reaction by IOB was mediated by an extracellular enzyme protein that requires oxygen. Radiotracer experiments showed that IOB produce not only I2 but also volatile organic iodine, which were identified as diiodomethane (CH2I2) and chloroiodomethane (CH2ClI). These results indicate that at least two types of IOB are distributed in the environment, and that they are preferentially isolated in environments in which iodide levels are very high. It is possible that IOB oxidize iodide in the natural environment, and they could significantly contribute to the biogeochemical cycling of iodine.

A furan fatty acid and indoxyl sulfate are the putative inhibitors of thyroxine hepatocyte transport in uremia

Abstract: We studied the effects of 3-carboxy-4-methyl-5-propyl-2-furan-propanoic acid (CMPF), indoxyl sulfate, and hippuric acid on iodide production by rat hepatocytes in primary cultures. We questioned whether these substances could explain the alteration of serum thyroid hormone parameters observed in renal failure. Iodide production from [125I]T4 by rat hepatocytes was significantly inhibited in the presence of serum from uremic patients. Serum concentrations of CMPF, indoxyl sulfate, and hippuric acid were markedly elevated in uremic patients. The minimum concentration that inhibited iodide production, when expressed as a molar ratio of the inhibitor to BSA, was 0.13 for CMPF, 0.53 for indoxyl sulfate, and 1.33 for hippuric acid. This molar ratio was lower than the corresponding mean molar ratio in uremic sera for CMPF (0.38) and indoxyl sulfate (0.63), while it was higher than that found for hippuric acid (0.85). The inhibition was reproduced when the inhibitors were added to normal human serum. The decreased iodide production was not due to the inhibition of deiodinase activity. The deiodination of rT3 by rat liver microsomes was unaffected by these inhibitors. Charcoal adsorption of uremic serum normalized the iodide production by hepatocytes. This normalization coincided with almost complete removal of CMPF and indoxyl sulfate, with a concomitant reduction of the free T4 fraction. Dialysis of uremic serum only partially restored iodide production. Even though indoxyl sulfate and hippuric acid were no longer detectable, a high concentration of CMPF remained in the serum. The serum free T4 fraction remained elevated in uremic patients after dialysis. Our studies indicate that CMPF and indoxyl sulfate in concentrations normally present in the serum of uremic patients inhibit cellular transport and subsequent deiodination of T4. These substances may account for the low total T3 level in uremic patients.

Iodine nutrition: iodine content of iodized salt in the United States.

Abstract: Adequacy of iodine nutrition in the United States has lately been of concern. A major source of dietary iodine for the U.S. population is iodized salt. The U.S. Food and Drug Administration (USFDA) recommends 60–100 mg KI/kg salt, equivalent to 46–76 mg I/kg salt. All U.S. iodized salt contains 45 mg I/kg according to labels. We collected samples of table salt from freshly opened containers from U.S. volunteers. A sample was sent to us when the can was first purchased. Subsets of volunteers sent further samples when the salt container became half-empty through normal use and a further final sample when the container was nearly finished. We also looked at iodine distribution homogeneity within individual containers, loss of iodine from salt upon exposure to humidity and sunlight, and upon short-term heating (dry and in solution) as may be encountered in cooking. Measurements were made in 0.01% w/v salt solutions by induction coupled plasma−mass spectrometry with 72Ge as an internal standard. The median and...