Thiourea and cyanamide as inhibitors of thyroid peroxidase: the role of iodide.

doi:10.1210/ENDO-104-4-919

Paper

Thiourea and cyanamide as inhibitors of thyroid peroxidase: the role of iodide.

Published Apr 1, 1979 · B. Davidson, M. Soodak, H. Strout

Endocrinology

Q1 SJR score

29

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0

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Abstract

Thiourea, methylmercaptoimidazole, propylthiouracil, and thiouracil are all potent inhibitors of thyroid peroxidase (TPO)-catalyzed iodination. Unlike the cyclic thioureylenes, thiourea at 5 mM has no effect on guaiacol oxidation. If iodide is added to guaiacol assays containing thiourea, enzyme activity is lost. The latter observation may be explained as follows. In the presence of iodide, the iodinating species [TPO.Ioxid], oxidizes thiourea to formamidine disulfide. This product decomposes to cyanamide at neutral pH. We have shown cyanamide to be an inhibitor of the peroxidative and iodinating functions of TPO. Studies in rats demonstrate that doses of thiourea which completely inhibit in vivo protein-bound iodine formation have no irreversible effect on TPO, as measured by guaiacol peroxidation after removal of the thyroids. The major in vivo action of cyanamide is similar to that of thiourea. The data suggest that the primary in vivo and in vitro mode of action of thiourea is the reversible Ioxid-trapping mechanism. The anomalous inhibition of guaiacol peroxidation seen in the presence of thiourea plus iodide derives from the formation of formamide disulfide, followed by its nonenzymic decomposition to cyanamide.

Study Snapshot

Thiourea and cyanamide both inhibit thyroid peroxidase, with iodide playing a crucial role in their reversible Ioxid-trapping mechanism and guaiacol peroxidation inhibition.

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

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Paper

Thiourea and cyanamide as inhibitors of thyroid peroxidase: the role of iodide.

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References

Citations

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