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Braverman
Breast Milk Iodine and Perchlorate Concentrations in Lactating Boston-Area Women.Pearce EN, Leung AM, Blount BC, Bazrafshan HR, He X, Pino S, Valentin-Blasini L, Braverman LE. J Clin Endocrinol Metab. 2007 Feb 20; [Epub ahead of print]
"Context: Breastfed infants rely on adequate maternal dietary iodine intake.
Objective: To measure breast milk iodine and perchlorate, an inhibitor of iodide transport into the thyroid and potentially into breast milk, in Boston-area women.
Participants: 57 lactating healthy volunteers in the Boston area. Measurements: Breast milk iodine and perchlorate concentrations, and urine iodine, perchlorate, and cotinine concentrations were measured. For comparison, iodine and perchlorate levels in infant formulae were also measured.
Results: Median breast milk iodine content in 57 samples was 155 microg/L (range 2.7 - 1968 microg/L). Median urine iodine was 114 microg/L (range 25 - 920 microg/L). Perchlorate was detectable in all 49 breast milk samples (range 1.3 - 411 microg/L), all 56 urine samples (range 0.37 - 127 microg/L), and all 17 infant formulae samples (range 0.22 - 4.1 microg/L) measured. Breast milk iodine content was significantly correlated with urinary iodine per gram creatinine and urinary cotinine, but was not significantly correlated with breast milk or urinary perchlorate.
Conclusions: Perchlorate exposure was not significantly correlated with breast milk iodine concentrations. Perchlorate was detectable in infant formula, but at lower levels than in breast milk. 47% of women sampled may have been providing breast milk with insufficient iodine to meet infants' requirements."
Effects of six months of daily low-dose perchlorate exposure on thyroid function in healthy volunteers.Braverman LE, Pearce EN, He X, Pino S, Seeley M, Beck B, Magnani B, Blount BC, Firek A. J Clin Endocrinol Metab. 2006 Jul;91(7):2721-4. Epub 2006 Apr 24. [abstract only]
"CONTEXT: Perchlorate
has been detected in U.S. drinking water supplies at levels
ranging from 4 to 200 microg/liter as well as in agricultural
products. Perchlorate is known to be a competitive inhibitor of
iodine uptake by the thyroid through the sodium-iodide symporter.
OBJECTIVE: The objective of the study was to determine whether
prolonged exposure (6 months) to low levels of perchlorate would
perturb thyroid function. DESIGN: This was a prospective,
double-blinded, randomized trial. PARTICIPANTS: The study
population consisted of 13 healthy volunteers. Intervention:
Interventions included placebo vs. 0.5 mg or 3.0 mg potassium
perchlorate daily. MAIN OUTCOME MEASURES: Serum thyroid function
tests, 24-h radioactive iodine uptake, serum thyroglobulin (Tg),
urinary iodine and perchlorate, and serum perchlorate were
measured. RESULTS: Mean urinary perchlorate value during
ingestion of 0.5 mg perchlorate daily was 332.7 +/- 66.1 microg
per 24 h or 248.5 +/- 64.5 microg/g creatinine and mean values
for the four subjects who received 3 mg perchlorate daily were
2079.5 +/- 430.0 microg per 24 h or 1941.7 +/- 138.5 microg/g
creatinine. There was no significant change in the thyroid (123)I
uptakes during perchlorate administration. There were no
significant changes in serum T(3), free T(4) index, TSH, or Tg
concentrations during the exposure period, compared to baseline
or postexposure values. Urine iodine values for the 3-mg
perchlorate group were higher, but not significantly so, at
baseline than during perchlorate exposure. CONCLUSIONS: We
observed that a 6-month exposure to perchlorate at doses up to 3
mg/d had no effect on thyroid function, including inhibition of
thyroid iodide uptake as well as serum levels of thyroid
hormones, TSH, and Tg." |
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