title: Perchlorate versus other environmental sodium/iodide symporter inhibitors: potential thyroid-related health effects.
abstract: OBJECTIVE
  Perchlorate is a known competitive inhibitor of the sodium/iodide symporter (NIS). Possible thyroid-related effects of environmental perchlorate have created great health concerns, especially in the US, resulting in a debated reference dose (RfD) of 0.0007 mg/kg per day in drinking water recommended by the National Academy of Sciences (NAS). However, the impact of other environmental NIS inhibitors and the role of iodine seem to have received little attention in the whole debate.
  
  
  METHODS
  We performed a PubMed search for articles published up to February 2006, using the key terms perchlorate, nitrate, thiocyanate, iodine, NIS, RfD, thyroid (alone or in combinations), with particular attention for human studies. In parallel, we critically analysed the January 2005 NAS' report, entitled 'Health implications of perchlorate ingestion'.
  
  
  RESULTS
  The relative potencies of prevalent environmental NIS inhibitors (nitrate, thiocyanate and perchlorate) to inhibit iodine uptake have been estimated repeatedly with robust results. Our calculations show that nitrate and thiocyanate, acquired through drinking water or food, account for a much larger proportion of iodine uptake inhibition than perchlorate. Furthermore, the iodine uptake inhibitory effects of nitrate and thiocyanate - as defined by their legally accepted maximal contaminant levels in drinking water - exceed the potential effect of the proposed RfD for perchlorate by far.
  
  
  CONCLUSIONS
  Iodine uptake inhibition and any potential downstream effect by perchlorate are highly dependent on the presence of other environmental NIS inhibitors and iodine intake itself. These potential confounders should therefore be considered in future studies and calculations for risk assessment.
authors.affiliation: Laboratory of Experimental Medicine and Endocrinology (LEGENDO), Faculty of Medicine and.
authors.forename: Bert
authors.initials: B
authors.lastname: De Groef
authors.forename: Brigitte R
authors.initials: BR
authors.lastname: Decallonne
authors.forename: Serge
authors.initials: S
authors.lastname: Van der Geyten
authors.forename: Veerle M
authors.initials: VM
authors.lastname: Darras
authors.forename: Roger
authors.initials: R
authors.lastname: Bouillon
mesh_terms: D000818:Animals; D004032:Diet; D004785:Environmental Pollutants / Q000633:toxicity*; D005504:Food Analysis; D006801:Humans; D007455:Iodine / Q000494:pharmacology; D009566:Nitrates / Q000633:toxicity; D019055:No-Observed-Adverse-Effect Level; D010472:Perchlorates / Q000633:toxicity*; D027981:Symporters / Q000037:antagonists & inhibitors*; D013861:Thiocyanates / Q000633:toxicity; D013959:Thyroid Diseases / Q000139:chemically induced*; D014874:Water Pollutants, Chemical / Q000633:toxicity; D000099209:Sodium-Iodide Symporters
chemical_list: D004785:Environmental Pollutants; D007455:Iodine; D009566:Nitrates; D010472:Perchlorates; D027981:Symporters; D013861:Thiocyanates; D014874:Water Pollutants, Chemical; D000099209:Sodium-Iodide Symporters; C494474:perchlorate