2018: Are Populations with Low Iodine Intakes More Vulnerable to Thyroid-Disrupting Effects of Perfluorinated Alkyl Acid

[pfpcnews]

ISES-ISEE 2018 Joint Annual Meeting: Addressing Complex Local and Global Issues in Environmental Exposure and Health
Glynn et al. - "Are Populations with Low Iodine Intakes More Vulnerable to Thyroid-Disrupting Effects of Perfluorinated Alkyl Acids (PFAAs)?"
ISEE Conference Abstracts 2018(1) (2018)
https://doi.org/10.1289/isesisee.2018.O04.01.43

Abstract:

It has been proposed that populations exhibiting a "stressed" thyroid system may be susceptible to perfluoroalkyl acid (PFAA) exposure (1). In this study, we explored the correlations between serum PFAA and thyroid hormone (TH) levels (TSH, free T4, free T3) in 10-12-year-old children (N=181) and assessed whether these associations varied based on iodine intake (urinary iodine). Serum PFAAs (12 homologues) and THs were quantified using LC/MS/MS and standard clinical methods, respectively, while urinary iodine was determined using a modified Sandell-Kolthoff method. Multiple linear regression analyses incorporated covariates such as child sex, BMI, nursing, maternal birth country, parental education, number of older siblings, passive smoking, and urine iodine. Participants were stratified into a low iodine group (urine iodine concentrations <median, N=90) and a high iodine group (≥median, N=91).

Across all study participants, statistically significant (p≤0.05) negative associations were identified for free T3 concerning PFOS (β coefficient -0.087±0.030, mean±SE), PFNA (-0.40±0.15), PFDA (-1.9±0.56), and PFUnDA (-1.2±0.50), as well as for PFOA and TSH (-0.13±0.060). Significant relationships were also observed between PFOS and free T4 (0.20±0.086) and between PFHpA and free T3 (2.4±1.2). Notably, these associations appeared more pronounced in the low iodine group than in the high iodine group. In the low iodine group, significant free T3 associations were noted for PFOS (-0.089 ± 0.041), PFDA (-2.4 ± 0.81), and PFHpA (3.8 ± 1.8), with the TSH association being significant for PFOA (-0.22 ± 0.082). Although not statistically significant in the overall study group, the association between PFHxS and free T3 was significant in the low iodine group (-0.052 ± 0.019). These findings suggest that the thyroid-disrupting effects of PFAAs may be more pronounced in populations with low iodine intakes, although the cross-sectional design and the limited sample size warrant caution in drawing definitive conclusions (1).

Reference:
(1) Webster GM, et al. 2016. Environ Health Perspect 124, 935-942.