Exogenous iodide ameliorates perchlorate-induced thyroid phenotypes in threespine stickleback.

Area of Science:

• Environmental toxicology
• Endocrinology
• Aquatic toxicology

Background:

• Perchlorate is a widespread environmental contaminant.
• It causes endocrine disruption in vertebrates, targeting thyroid tissue.
• Effects include altered thyroid follicle organization, activation, and morphology.

Purpose of the Study:

• To investigate if perchlorate toxicity phenotypes are mediated by thyroid hormone.
• To examine the effects of iodide and thyroxine (T4) supplementation on perchlorate-induced toxicity.
• To assess temporal differences in response before and after sexual maturation.

Main Methods:

• Chronic exposure of threespine stickleback (Gasterosteus aculeatus) to perchlorate (10, 30, 100ppm) from fertilization.
• Concurrent supplementation with iodide or thyroxine (T4) or control water.
• Sampling across a one-year timespan for thyroid histomorphology and hormone analysis.

Main Results:

• Iodide supplementation ameliorated most perchlorate-induced thyroid histomorphological changes.
• Thyroxine (T4) supplementation did not correct thyroid histopathologies.
• Perchlorate exposure increased erythrocyte area (adults) and lipid droplet number (subadults), with mixed responses to supplementation.

Conclusions:

• Some perchlorate toxicity is not mediated by thyroid hormone.
• Iodide is effective in mitigating thyroid disruption, while T4 is not.
• Early perchlorate exposure may have obesogenic effects, indicated by increased lipid droplets.