The Effect of Maternal Exposure to Dioxins on the Level of Thyroid Hormone in Developing Pups

Yukiko Hattori, Tomoki Takeda, Junki Taura, Hiroaki Kuroki, Yuji Ishii, Hideyuki Yamada

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1 Citation (Scopus)

Abstract

Maternal exposure to dioxins causes a number of developmental disorders in the offspring. Previous studies have suggested that lactational exposure to 2,3,7,8-tetrachlorodizenzo-p-dioxin (TCDD) reduces the pup level of thyroid hormone after weaning, leading to the damage to their development including neural maturation. However, the specificity for age and dioxin congeners as well as dose dependency in terms of a reduction in pup thyroid hormone remains to be clarified. To address this issue, we investigated whether TCDD or 2,3,4,7,8-pentachlorodibenzofuran (PenCDF), one of the dioxins which caused 'Yusho' incident, affects the status of thyroid hormone during the fetal and neonatal periods. Treating pregnant rats at gestational day (GD)15 with 1 μg/kg TCDD scarcely affected the serum concentration of thyroxine, although a significant reduction by TCDD was detected at limited endpoints [GD21 and postnatal day (PND)21]. In addition, maternal exposure to TCDD (0.05-30 μg/kg) or PenCDF (1-1,000 μg/kg) did not have any change in the serum level of thyroxine in GD20 fetuses even at the maximum dose. Neither the expression of pituitary thyroid-stimulating hormone β (TSHβ) nor hypothalamic thyrotropin-releasing hormone was sensitive to TCDD treatment. In pregnant dams, TCDD decreased the serum level of thyroxine at GD20 and 21, while the pituitary expression of TSHβ was induced. These results suggest that a single administration of dioxins to pregnant rats at GD15 have little effect on the level of thyroxine in the fetuses and infants, while a reduced level of this hormone observed in the offspring at GD21 and PND21 and pregnant dams at GD20 and 21.

Original languageEnglish
Pages (from-to)127-134
Number of pages8
JournalFukuoka igaku zasshi = Hukuoka acta medica
Volume106
Issue number5
Publication statusPublished - May 1 2015

All Science Journal Classification (ASJC) codes

  • Medicine(all)

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