[CPEO-MEF] Genetic factors in perchlorate response

[Lenny Siegel <lsiegel@cpeo.org>]

Genetic Factors That Might Lead to Different Responses in Individuals 
Exposed to Perchlorate

Franco Scinicariello, H. Edward Murray, Lester Smith, Sharon Wilbur, and 
Bruce A. Fowler

Division of Toxicology, Agency for Toxic Substances and Disease 
Registry, Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Environmental Health Perspectives
November, 2005

Abstract
Perchlorate has been detected in groundwater in many parts of the United 
States, and recent detection in vegetable and dairy food products 
indicates that contamination by perchlorate is more widespread than 
previously thought. Perchlorate is a competitive inhibitor of the sodium 
iodide symporter, the thyroid cell-surface protein responsible for 
transporting iodide from the plasma into the thyroid. An estimated 4.3% 
of the U.S. population is subclinically hypothyroid, and 6.9% of 
pregnant women may have low iodine intake. Congenital hypothyroidism 
affects 1 in 3,000 to 1 in 4,000 infants, and 15% of these cases have 
been attributed to genetic defects. Our objective in this review is to 
identify genetic biomarkers that would help define subpopulations 
sensitive to environmental perchlorate exposure. We review the 
literature to identify genetic defects involved in the iodination 
process of the thyroid hormone synthesis, particularly defects in iodide 
transport from circulation into the thyroid cell, defects in iodide 
transport from the thyroid cell to the follicular lumen (Pendred 
syndrome), and defects of iodide organification. Furthermore, we 
summarize relevant studies of perchlorate in humans. Because of 
perchlorate inhibition of iodide uptake, it is biologically plausible 
that chronic ingestion of perchlorate through contaminated sources may 
cause some degree of iodine discharge in populations that are 
genetically susceptible to defects in the iodination process of the 
thyroid hormone synthesis, thus deteriorating their conditions. We 
conclude that future studies linking human disease and environmental 
perchlorate exposure should consider the genetic makeup of the 
participants, actual perchlorate exposure levels, and individual iodine 
intake/excretion levels.

For the complete description as well as links to the full article in 
either HTML or PDF format, go to
http://ehp.niehs.nih.gov/docs/2005/8076/abstract.html
--
Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
http://www.cpeo.org

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