TH and thyroid gland carcinoma: Studies showing disruption of thyroid hormone functions after As exposure in rodents include an increase in thyroid cancer (Yamamoto 1995), a synergistic effect between As and TH on oxidative stress (Allen and Rana 2003), and a disregulation of deiodinase levels in fetal brain with concurrent As exposure and selenium depletion (Miyazaki et al. 2005).