Sex‐specific changes in thyroid gland function and circulating thyroid hormones in nestling American kestrels ( Falco sparverius) following embryonic exposure to polybrominated diphenyl ethers by maternal transfer

• Published in: Environmental Toxicology and Chemistry
• Main Authors: Fernie, Kim J., Marteinson, Sarah C.
• Other Authors: Natural Sciences and Engineering Research Council of Canada, Environment Canada
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Avian Studies
• Online Access: http://dx.doi.org/10.1002/etc.3366; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fetc.3366; https://setac.onlinelibrary.wiley.com/doi/pdf/10.1002/etc.3366

Abstract High concentrations of polybrominated diphenyl ethers (PBDEs) accumulate in predatory birds. Several PBDE congeners are considered thyroid disruptors; however, avian studies are limited. The authors examined circulating thyroid hormones and thyroid gland function of nestling American kestrels ( Falco sparverius ) at 17 d to 20 d of age, following embryonic exposure by maternal transfer only to environmentally relevant levels of PBDEs (DE‐71 technical mixture). Nestlings were exposed to in ovo sum (Σ) PBDE concentrations of 11 301 ± 95 ng/g wet weight (high exposure), 289 ± 33 ng/g wet weight (low exposure), or 3.0 ± 0.5 ng/g wet weight (controls, background exposure). Statistical comparisons are made to controls of the respective sexes and account for the relatedness of siblings within broods. Circulating concentrations of plasma total thyroxine (TT 4 ) and total triiodothyronine (TT 3 ) in female nestlings were significantly influenced overall by the exposure to DE‐71. Following intramuscular administration of thyroid‐stimulating hormone, the temporal response of the thyroid gland in producing and/or releasing TT 4 was also significantly affected by the females' exposure to DE‐71. The altered availability of T 4 for conversion to T 3 outside of the gland and/or changes in thyroid‐related enzymatic activity may explain the lower TT 3 concentrations (baseline, overall) and moderately altered temporal TT 3 patterns ( p = 0.06) of the treatment females. Controlling for the significant effect on TT 3 levels of the delayed hatching of treatment females, baseline TT 3 levels were significantly and positively correlated with body mass (10 d, 15 d, 20 d), with PBDE‐exposed females generally being smaller and having lower TT 3 concentrations. Given that exposure concentrations were environmentally relevant, similar thyroidal changes and associated thyroid‐mediated processes relating to growth may also occur in wild female nestlings. Environ Toxicol Chem 2016;35:2084–2091. © 2016 SETAC