Hypothyroidism and Environmental Endocrine Disruption
Hypothyroidism affects approximately 5% of adults globally, with higher prevalence in women. Thyroid function is exquisitely sensitive to environmental chemicals that interfere with iodine metabolism and thyroid hormone synthesis.
PFAS Mechanisms of Thyroid Disruption
PFAS compete with thyroid hormones for binding to thyroid hormone transport proteins including transthyretin, reducing free hormone bioavailability. Additionally, PFAS inhibit thyroid peroxidase (TPO) activity, impairing T3 and T4 synthesis.
Clinical and Epidemiological Evidence
Large cross-sectional studies show inverse associations between PFAS serum levels and free T4 concentrations. TSH elevation—indicative of subclinical hypothyroidism—is more prevalent in PFAS-contaminated communities.
Treatment Considerations
Endocrinologists managing subclinical or overt hypothyroidism should screen for PFAS exposure, particularly in communities with contaminated water supplies. Levothyroxine dose optimization may need environmental context.