Potassium iodide changes the levels of thyroid hormones in goitrogenic rats on selenium deficient diet.

OBJECTIVE: A possible link was proposed between selenium [Se(-)], iodine deficiency and thyroid pathology. The aim of the study was to examine changes in FT3 and FT4 concentrations, weights of the thyroid glands and ioduria after potassium iodide (KI) in normal and goitrogenic rats on Se(-) diet.

METHODS: Wistar rats in Group 1 received the standard diet. Other animals remained (3 months) either on a Se(-) diet alone [Groups 2-5] or supplemented with selenium [Se(+)] (Group 6-8). After 9 weeks, Groups 3, 4, 6, 7 received sodium perchlorate [I(-); 1 month]. KI (1 mg/rat) was injected in Groups 4, 5, 7, 8. The animals were decapitated 3 days after the injections.

RESULTS: FT4 was higher in serum of Se(-) rats than in that of Se(+). The differences of FT3 were not statistically significant. In I(-) Groups, the levels of FT3 and FT4 were very low. KI increased both thyroid hormones in I(-) rats but the effect was especially pronounced for FT3. KI decreased the weights of the glands, enlarged in the I(-) animals, both on Se(-) and Se(+) diet. Urine iodide concentrations were lower in Se(-) animals; KI increased ioduria.

CONCLUSIONS: These data demonstrate that selenium and iodine deficiencies may play an essential role in thyroid hormone metabolism.

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