THE FULL ARTICLE TITLE
Curtis SW et al 2019 Thyroid hormone levels associate with exposure to polychlorinated biphenyls and polybrominated biphenyls in adults exposed as children. Environ Health 18:75. PMID: 31443693.
SUMMARY OF THE STUDY
For this study, 717 participants in the Michigan PBB Registry provided serum samples between 2004 and 2015. In these samples, 4 types of PBB and 4 types of PCBs were measured. Participants who were known to take thyroid medications were excluded. To evaluate outcomes, serum TSH, free T4, T4 and free T3 were measured.
The study population was 61.6% female, average age of exposure was 14 years, 446 were exposed before puberty and 269 after completion of puberty. The participants were found to have PCBs levels similar to those found in representative samples of the United States. However, 92% of participants had higher PBB levels when comparing to the rest of the U.S population. Older participants had higher levels of PBB and PCB; men had higher levels of both than women.
A higher PBB concentration was associated with a lower free T4 and a higher free T3 and this association was observed mainly in participants who were exposed before completion of puberty. A higher PCB concentration was associated with a higher free T4. There was no association of either chemical with TSH, total T4 or total T3.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The conclusion of this study is that exposure to PBBs during early life is associated with lower free T4 and higher free T3 concentrations during later life. Although the associations between thyroid hormone levels and PBB in this study are not consistent with actual clinical thyroid disease (the majority of the samples were within usual ranges for population), variation in thyroid hormone levels within their normal ranges can still impact health. Therefore, people with higher exposure to PBBs may be at greater risk for metabolic and reproductive problems even if their hormone levels are still within the usual population range. This is especially true about the people exposed as children. Further study of this population is needed to determine the health implications of this exposure.
— Jessie Block-Galarza, MD