Thyroid function tests in persons with occupational exposure to fipronil.

Background: Fipronil represents a chemical class of insecticides acting at the γ-aminobutyric acid receptor in pests. [corrected] Fipronil has been associated with a significant increase in the incidence of thyroid gland tumors concomitant with prolonged exposure to thyroid-stimulating hormone (TSH) in rats. An association between human TSH concentration and thyroid cancer has been also reported.