Temporal patterns in perchlorate, thiocyanate, and iodide excretion in human milk
Andrea B Kirk1, Jason V Dyke, Clyde F Martin
1Department of Chemistry, University of Texas at Arlington, Arlington, TX 76009-0065, USA.
Insights
Perchlorate and thiocyanate are common in human milk, potentially reducing iodide levels. Further research is needed to understand their impact on thyroid hormone synthesis and iodine intake.
Area of Science:
- Environmental Health
- Endocrinology
- Human Nutrition
Background:
- Perchlorate and thiocyanate can disrupt thyroid hormone synthesis by interfering with iodide uptake.
- Perchlorate is a widespread contaminant found in water, food, and human milk.
- While serum and urinary iodide levels show diurnal variations, milk iodide variations are less understood.
Purpose of the Study:
- To examine the variability of perchlorate, thiocyanate, and iodide in human milk.
- To investigate the excretion patterns of these substances in serially collected milk samples.
Main Methods:
- Ten lactating women provided serial human milk samples over three days.
- Milk samples were analyzed for perchlorate, iodide, and thiocyanate using ion chromatography coupled with mass spectrometry.
Main Results:
- Significant individual and temporal variations were observed for perchlorate, iodide, and thiocyanate levels in human milk.
- Mean iodide levels were 87.9 microg/L, perchlorate 5.8 microg/L, and thiocyanate 35.6 microg/L, with considerable variation.
- Data distribution showed means higher than medians, indicating skewed levels for all measured substances.
Conclusions:
- Perchlorate and thiocyanate are prevalent in human milk.
- Inadequate iodine intake may affect a substantial portion of the studied population.
- The impact of perchlorate and thiocyanate on reducing breast milk iodide requires further investigation.
Background:
Perchlorate and thiocyanate interfere with iodide uptake at the sodium-iodide symporter and are potential disruptors of thyroid hormone synthesis. Perchlorate is a common contaminant of water, food, and human milk. Although it is known that iodide undergoes significant diurnal variations in serum and urinary excretion, less is known about diurnal variations of milk iodide levels.
Objectives:
Variability in perchlorate and thiocyanate excretion in human milk has not been examined. Our objective was to determine variability of perchlorate, thiocyanate, and iodide in serially collected samples of human milk.
Methods:
Ten lactating women were asked to collect six milk samples on each of 3 days. As an alternative, subjects were asked to collect as many milk samples as comfortably possible over 3 days. Samples were analyzed for perchlorate, iodide, and thiocyanate by ion chromatography coupled with mass spectrometry.
Results:
Individual perchlorate, iodide, and thiocyanate levels varied significantly over time; there was also considerable variation among individuals. The iodide range, mean +/- SD, and median for all samples (n = 108) were 3.1-334 microg/L, 87.9 +/- 80.9 microg/L, and 55.2 microg/L, respectively. The range, mean +/- SD, and median of perchlorate in all samples (n = 147) were 0.5-39.5 microg/L, 5.8 +/- 6.2 microg/L, and 4.0 microg/L. The range, mean +/- SD, and median of thiocyanate in all samples (n = 117) were 0.4 -228.3 microg/L, 35.6 +/- 57.9 microg/L, and 5.6 microg/L. The data are not symmetrically distributed; the mean is higher than the median in all cases.
Conclusions:
Iodine intake may be inadequate in a significant fraction of this study population. Perchlorate and thiocyanate appear to be common in human milk. The role of these chemicals in reducing breast milk iodide is in need of further investigation.
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