title: Thyroid function tests in persons with occupational exposure to fipronil.
abstract: 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. The primary objective of this study was to test the hypothesis that chronic occupational fipronil exposure may be associated with abnormal thyroid function tests.
  
  
  METHODS
  In 2008, 159 workers of a factory manufacturing fipronil-containing veterinary drugs were assessed. Serum concentrations of TSH, total thyroxine, free thyroxine, fipronil, and fipronil sulfone were measured.
  
  
  RESULTS
  A positive and significant correlation was observed between serum fipronil or fipronil sulfone levels and duration of fipronil exposure. Serum fipronil sulfone concentration was negatively correlated with TSH concentration in fipronil-exposed workers, but with no significant increase in thyroid function test abnormalities.
  
  
  CONCLUSIONS
  This study did not show that chronic fipronil exposure was associated with an increase of thyroid function test abnormalities. But, despite the fact that fipronil exposure in rats has been associated with increased serum TSH, fipronil sulfone concentrations were negatively correlated with serum TSH concentrations in fipronil-exposed workers, raising the possibility that fipronil has a central inhibitory effect on TSH secretion in humans. Close occupational medical surveillance, therefore, appears to be required in factory workers manufacturing fipronil-containing veterinary drugs. Larger epidemiological studies as well as investigations on possible thyroid-disrupting mechanisms of fipronil are also required.
authors: 1 Inserm U558, National Institute of Health and Medical Research (INSERM) and The University Paul Sabatier, Toulouse, France.
authors: Fabrice
authors: F
authors: Herin
authors: Elisa
authors: E
authors: Boutet-Robinet
authors: Aude
authors: A
authors: Levant
authors: Sylvain
authors: S
authors: Dulaurent
authors: Mimoza
authors: M
authors: Manika
authors: Florence
authors: F
authors: Galatry-Bouju
authors: Philippe
authors: P
authors: Caron
authors: Jean-Marc
authors: JM
authors: Soulat