Thyroid function changes related to use of iodinated water in the U.S. Space Program.
BACKGROUND
The National Aeronautics and Space Administration (NASA) has used iodination as a method of microbial disinfection of potable water systems in U.S. spacecraft and long-duration habitability modules. A review of thyroid function tests of NASA astronauts who had consumed iodinated water during spaceflight was conducted.


METHODS
Thyroid function tests of all past and present astronauts were reviewed. Medical records of astronauts with a diagnosis of thyroid disease were reviewed. Iodine consumption by space crews from water and food was determined. Serum thyroid-stimulating hormone (TSH) and urinary iodine excretion from space crews were measured following modification of the Space Shuttle potable water system to remove most of the iodine.


RESULTS
Mean TSH significantly increased in 134 astronauts who had consumed iodinated water during spaceflight. Serum TSH, and urine iodine levels of Space Shuttle crewmembers who flew following modification of the potable water supply system to remove iodine did not show a statistically significant change. There was no evidence supporting association between clinical thyroid disease and the number of spaceflights, amount of iodine consumed, or duration of iodine exposure.


CONCLUSIONS
It is suggested that pharmacological doses of iodine consumed by astronauts transiently decrease thyroid function, as reflected by elevated serum TSH values. Although adverse effects of excess iodine consumption in susceptible individuals are well documented, exposure to high doses of iodine during spaceflight did not result in a statistically significant increase in long-term thyroid disease in the astronaut population.
McMonigal
K A
KA
Space and Life Sciences Directorate, NASA-Johnson Space Center, Houston, TX 77058, USA. kathleen.a.mcmonigal1@jsc.nasa.gov
Braverman
L E
LE
Dunn
J T
JT
Stanbury
J B
JB
Wear
M L
ML
Hamm
P B
PB
Sauer
R L
RL
Billica
R D
RD
Pool
S L
SL
D018480:Astronauts; D005260:Female; D006801:Humans; D007454:Iodides / Q000009:adverse effects* / Q000032:analysis; D007455:Iodine / Q000009:adverse effects* / Q000032:analysis / Q000652:urine; D008297:Male; D009784:Occupational Diseases / Q000097:blood / Q000139:chemically induced* / Q000145:classification / Q000652:urine; D016273:Occupational Exposure / Q000009:adverse effects* / Q000032:analysis; D011446:Prospective Studies; D012189:Retrospective Studies; D013026:Space Flight; D018531:Spacecraft; D013959:Thyroid Diseases / Q000097:blood / Q000139:chemically induced* / Q000145:classification / Q000652:urine; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood* / Q000187:drug effects*; D013997:Time Factors; D014481:United States; D018557:United States National Aeronautics and Space Administration; D018508:Water Purification / Q000379:methods*
D007454:Iodides; D013972:Thyrotropin; D007455:Iodine