The presence of perchlorate (ClO(4) (-)) in some U.S. drinking water supplies has raised concern about potential adverse thyroidal health effects, because ClO(4) (-) is known to competitively inhibit iodide uptake at the sodium iodide symporter (NIS). Humans are nutritionally and environmentally exposed to other competitive inhibitors of iodide uptake, including thiocyanate (SCN(-)) and nitrate (NO(3) (-)). The joint inhibiting effects of these three anions was studied by exposing Chinese hamster ovary cells stably expressing human NIS to varying concentrations of each anion separately, and in combination, and conducting measurements of (125)I(-) uptake. The entire data set was fit to a single Hill equation using maximum likelihood. The relative potency of ClO(4) (-) to inhibit (125)I(-) uptake at the NIS was found to be 15, 30 and 240 times that of SCN(-), I(-), and NO(3) (-) respectively on a molar concentration basis, with no evidence of synergism. These results are consistent with a common mode of action by these anions of simple competitive interaction, in which a concentration of any one of ClO(4) (-) SCN(-), and NO(3) (-), occurring either individually or as part of a mixture of the three anions, is indistinguishable from a concentration or dilution of either one of the remaining two ions in inhibiting iodine uptake at the NIS.

3-iodothyronamine (T1AM) is a novel relative of thyroid hormone, able to interact with specific G protein-coupled receptors, known as trace amine-associated receptors. Significant functional effects are produced by exogenous T1AM, including a negative inotropic and chronotropic effect in cardiac preparations. This work was aimed at estimating endogenous T1AM concentration in different tissues and determining its cardiac metabolism. A novel HPLC tandem mass spectrometry assay was developed, allowing detection of T1AM, thyronamine, 3-iodothyroacetic acid, and thyroacetic acid. T1AM was detected in rat serum, at the concentration of 0.3±0.03 pmol/ml, and in all tested organs (heart, liver, kidney, skeletal muscle, stomach, lung, and brain), at concentrations significantly higher than the serum concentration, ranging from 5.6±1.5 pmol/g in lung to 92.9±28.5 pmol/g in liver. T1AM was also identified for the first time in human blood. In H9c2 cardiomyocytes and isolated perfused rat hearts, significant Na+-dependent uptake of exogenous T1AM was observed, and at the steady state total cellular or tissue T1AM concentration exceeded extracellular concentration by more than 20-fold. In both preparations T1AM underwent oxidative deamination to 3-iodothyroacetic acid. T1AM deamination was inhibited by iproniazid but not pargyline or semicarbazide, suggesting the involvement of both monoamine oxidase and semicarbazide-sensitive amine oxidase. Thyronamine and thyroacetic acid were not detected in heart. Finally, evidence of T1AM production was observed in cardiomyocytes exposed to exogenous thyroid hormone, although the activity of this pathway was very low.

Both mRNA and protein expression of the chemokines IP-10/CXCL10 and Mig/CXCL9, as well as of their receptor, CXCR3, were assessed in the thyroid glands of 16 patients suffering from Graves' disease (GD). In addition, IP-10/CXCL10 levels were measured in the serum of 50 GD patients. Expression of IP-10/CXCL10, Mig/CXCL9, and CXCR3 was poor or absent in normal thyroid tissue from patients undergoing thyroidectomy because of primary localized thyroid tumors, while both the chemokines and their receptor were present in most thyroid glands of patients affected by GD. IP-10/CXCL10 and Mig/CXCL9 localized to infiltrating lymphocytes and macrophages, as well as to resident epithelial follicular cells, whereas CXCR3 was mainly found at the level of infiltrating inflammatory cells and endothelial cells from large and small vessels. Of note, maximal expression of IP-10/CXCL10 and Mig/CXCL9 was found in the thyroid gland of patients with recent-onset GD and was correlated with interferon (IFN)-gamma. Accordingly, high levels of IP-10/CXCL10 could be measured in the serum of patients with short-duration GD. Taken together, the results of this study demonstrate that the CXCR3-binding chemokines IP-10/CXCL10 and Mig/CXCL9 play an important role in the recruitment of cells and in the amplification of inflammation in GD. They also suggest that the production of these chemokines by resident follicular epithelial cells may contribute to the recruitment of CXCR3-expressing type 1 T-helper cells in the initial phases of GD.

A series of somatic mutations of the TSH receptor gene have been demonstrated in hyperfunctioning thyroid adenomas. The mutations studied up to now cause constitutive (i.e. TSH-independent) activation of the cAMP-regulatory cascade only. As a follow-up to our original study, we have now completely sequenced exon number 10 of the TSH receptor gene in the same series of toxic adenomas. An activating mutation was found in nine of 11 tumors. In addition to the mutations already described, two isoleucine residues belonging to the first and second extracellular loops of the receptor (Ile486 and Ile568) were found mutated. Two different adenomas were found to harbor a different amino acid substitution at residue 486 (Ile486Phe, Ile486Met). Ile568 was mutated to threonine in one. When studied by transfection in COS-7 cells, all three mutations caused very strong activation of the cAMP-regulatory cascade. In addition, the Ile486Phe and, to a lesser extent, the Ile486Met and Ile568Thr mutants stimulated constitutively the inositol phosphate-diacylglycerol cascade. Our results demonstrate that 1) the first and second extracellular loops contribute to the silencing of the unliganded TSH receptor; 2) the two regulatory cascades normally under TSH control can be constitutively activated by somatic mutations of the receptor; 3) the TSH receptor can be activated by mutation of a large number of residues distributed over the first and second extracellular loops, the third intracellular loop, and the third, sixth, and seventh transmembrane segments; 4) activating mutations of the TSH receptor constitute the major cause of toxic adenomas, accounting for about 80% of the cases.

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