Early postnatal decabromodiphenyl ether exposure reduces thyroid hormone and astrocyte density in the juvenile mouse dentate gyrus

•Decabromodiphenyl ether is the fully brominated member of the PBDE flame retardants.•Decabromodiphenyl ether has become a global environmental contaminant.•Decabromodiphenyl ether is a thyroid hormone disrupter.•Thyroid hormone disruption during development reduces astrocytes in the hippocampus.•Altered development of the hippocampus can impair learning and memory. Decabromodiphenyl ether (decaBDE) is a flame retardant that was widely-applied to many consumer products for decades. Consequently, decaBDE and other members of its class have become globally-distributed environmental contaminants. Epidemiological and animal studies indicate that decaBDE exposure during critical periods of brain development produces long-term behavioral impairments. The current study was designed to identify potential neuroendocrine mechanisms for learning and response inhibition deficits observed by our lab in a previous study. C57BL6/J mouse pups were given a single daily oral dose of 0 or 20 mg/kg decaBDE from day 1 to 21. Serum thyroid hormone levels and astrocyte-specific staining in three regions of the hippocampus were measured on day 22. DecaBDE exposure significantly reduced serum triiodothyronine, thyroxine, and astrocyte density in the subgranular zone but not the hilus or granular layer in both male and female mice. The reduction of thyroid hormone and/or glia activity could impair hippocampal development, leading to behavior dysfunction.