From the Guidelines
There is evidence suggesting that Aqueous Film Forming Foam (AFFF) exposure may potentially contribute to hypothyroidism. AFFF contains per- and polyfluoroalkyl substances (PFAS), particularly PFOS and PFOA, which have been associated with thyroid hormone disruption in some studies 1. These chemicals can interfere with thyroid hormone production, transport, and metabolism by competing with natural thyroid hormones, affecting thyroid hormone receptors, and disrupting the hypothalamic-pituitary-thyroid axis. Some key points to consider:
- People with significant occupational exposure to AFFF, such as firefighters, military personnel at bases where AFFF was used, and those living near contaminated sites may be at higher risk.
- If you're concerned about AFFF exposure, consider having your thyroid function tested through blood tests measuring TSH, T3, and T4 levels.
- While a direct causal relationship hasn't been definitively established, the scientific evidence points to PFAS compounds potentially affecting thyroid function, making monitoring advisable for those with known exposure.
- The most common cause of hypothyroidism in the United States is chronic autoimmune (Hashimoto) thyroiditis, and risk factors for an elevated TSH level include female sex, advancing age, white race, type 1 diabetes, Down syndrome, family history of thyroid disease, goiter, previous hyperthyroidism, and external-beam radiation in the head and neck area 1. However, the evidence provided does not directly link AFFF exposure to hypothyroidism, and more research is needed to fully understand the relationship between AFFF and thyroid function. In clinical practice, it is essential to prioritize the patient's health and well-being, and if there is a suspicion of AFFF exposure, it is crucial to monitor thyroid function and adjust treatment accordingly.
From the Research
Aqueous Film Forming Foam (AFFF) and Hypothyroidism
- AFFF contains perfluoroalkyl substances (PFASs), which have been linked to thyroid disruption in several studies 2, 3, 4, 5, 6
- Exposure to PFASs has been shown to be associated with changes in thyroid hormone levels, including decreased total T4 and increased TSH 4, 6
- Firefighters, who are occupationally exposed to AFFF, have been found to have elevated serum levels of long-chain PFASs and an increased risk of thyroid cancer 3
- The mechanisms by which PFASs affect thyroid function are not fully understood, but may involve disruption of the hypothalamic-pituitary-thyroid axis and binding to thyroid receptors 5, 6
- Some studies have found correlations between PFAS exposure and thyroid hormone levels, including positive correlations between PFOS and free T4, and negative correlations between PFOA and total T4 4
- The effects of PFASs on thyroid function may vary depending on the specific compound, concentration, and population being studied 4, 6
Key Findings
- PFASs in AFFF have been linked to thyroid disruption and cancer risk in firefighters 3
- Exposure to PFASs has been associated with changes in thyroid hormone levels, including decreased total T4 and increased TSH 4, 6
- The mechanisms by which PFASs affect thyroid function are not fully understood, but may involve disruption of the hypothalamic-pituitary-thyroid axis and binding to thyroid receptors 5, 6
Population-Specific Effects
- Firefighters: elevated serum levels of long-chain PFASs and increased risk of thyroid cancer 3
- Infants: exposure to PFASs has been linked to congenital hypothyroidism 2
- Adults: exposure to PFASs has been associated with changes in thyroid hormone levels, including decreased total T4 and increased TSH 4, 6
- Pregnant women: exposure to PFASs has been linked to changes in thyroid hormone levels and fetal development 5, 6