Blount, B. C., Pirkle, J. L., Osterloh, J. D., Valentin-Blasini, L., & Caldwell, K. L. (2006). Urinary perchlorate and thyroid hormone levels in adolescent and adult men and women living in the United States. Environmental health perspectives. https://doi.org/10.1289/ehp.9466
Blount BC, Pirkle JL, Osterloh JD, Valentin-Blasini L, Caldwell KL. Urinary perchlorate and thyroid hormone levels in adolescent and adult men and women living in the United States. Environmental health perspectives. 2006. doi:10.1289/ehp.9466
Blount, B. C., et al. "Urinary perchlorate and thyroid hormone levels in adolescent and adult men and women living in the United States." Environmental health perspectives, 2006.
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RRM Academy Synopsis
Perchlorate exposure is linked to thyroid hormone changes in US women
In a cross-sectional analysis of a US national survey, perchlorate was linked to lower thyroxine and higher TSH in women with low iodine. Men showed no link between perchlorate and either hormone. The analysis covered 2,299 people aged 12 and older. Perchlorate is a chemical found in water and food, and TSH is thyroid stimulating hormone.
Key Findings
The analysis used 2,299 participants aged 12 and older from the 2001–2002 National Health and Nutrition Examination Survey (NHANES), with 1,111 women in the final women-only models.
Among women with low urinary iodine, higher perchlorate went with lower total thyroxine (T4, p < 0.0001) and higher TSH (p = 0.001).
Among women with higher urinary iodine, higher perchlorate went with higher TSH (p = 0.025) but showed no significant link to T4 (p = 0.550).
Men showed no significant link between perchlorate and T4 or TSH, including men with low urinary iodine.
The authors report that, for women with low urinary iodine, the predicted shifts in T4 and TSH at higher exposure can cover a sizable share of the normal range.
Interpretation
The study analyzes a CDC survey built to represent the civilian US population. Blood and urine were sampled once, so the results describe associations at a single point in time. Women who reported thyroid disease or thyroid medicine were excluded. The authors describe the pattern as consistent with perchlorate competing with iodide for uptake by the thyroid. Women with less iodine may be more vulnerable. The authors note the associations appeared at perchlorate exposure levels lower than earlier studies anticipated, and they recommend more research to confirm the findings.
RRM Context
Restorative reproductive medicine looks for root causes of hormone problems. Thyroid health belongs in that search. In this survey, the link between perchlorate and thyroid hormones differed by a woman's iodine status. The authors cite earlier work linking a mildly underactive thyroid in pregnancy to subtle deficits in children's thinking skills.
Our editorial summary of this paper, not the article's abstract.
Abstract
Background
Perchlorate is commonly found in the environment and known to inhibit thyroid function at high doses. Assessing the potential effect of low-level exposure to perchlorate on thyroid function is an area of ongoing research.
Objectives
We evaluated the potential relationship between urinary levels of perchlorate and serum levels of thyroid stimulating hormone (TSH) and total thyroxine (T4) in 2,299 men and women, > or = 12 years of age, participating in the National Health and Nutrition Examination Survey (NHANES) during 2001-2002.
Methods
We used multiple regression models of T4 and TSH that included perchlorate and covariates known to be or likely to be associated with T4 or TSH levels: age, race/ethnicity, body mass index, estrogen use, menopausal status, pregnancy status, premenarche status, serum C-reactive protein, serum albumin, serum cotinine, hours of fasting, urinary thiocyanate, urinary nitrate, and selected medication groups.
Results
Perchlorate was not a significant predictor of T4 or TSH levels in men. For women overall, perchlorate was a significant predictor of both T4 and TSH. For women with urinary iodine < 100 microg/L, perchlorate was a significant negative predictor of T4 (p < 0.0001) and a positive predictor of TSH (p = 0.001). For women with urinary iodine > or = 100 microg/L, perchlorate was a significant positive predictor of TSH (p = 0.025) but not T4 (p = 0.550).
Conclusions
These associations of perchlorate with T4 and TSH are coherent in direction and independent of other variables known to affect thyroid function, but are present at perchlorate exposure levels that were unanticipated based on previous studies.
