Endocrine Abstracts

Objectives: The worldwide incidence of thyroid cancer (TC) is increasing at an alarming rate in the last decades and environmental pollution has been suggested to be involved in this rise. Some environmental pollutants, namely endocrine disruptive chemicals (EDCs), have been linked to endocrine system disruption, including thyroid dysfunction, and increased risk of cancer. Among EDCs, per- and polyfluoroalkyl substances (PFAS) are widely used in many industrial and consumer products, including common household goods, and have raised global concern as persistent organic pollutants that threaten ecosystems and human health. To date few studies, mainly focused on high-risk populations, reported an association between PFAS and TC. The present case-control study aims to evaluate the possible association between serum PFAS concentrations and risk of thyroid cancer.

Materials and methods: We recruited 224 participants, of which 112 patients with a diagnosis of TC in the last five years and 112 sex and age-matched controls with no known history of thyroid diseases, primitive gonadic diseases, or other malignancies. Blood samples were taken from all participants and serum concentrations of some legacy PFAS were measured using liquid chromatography coupled to mass spectrometry. The possible association between serum PFAS levels and the risk of thyroid cancer was explored by the odds ratio (OR) and 95% confidence intervals (CI).

Results: The median age of case and control populations was 50 (range 20-89) and 51.5 (range 19-86) years respectively, with 77.7% of female participants in both groups. Among PFAS tested, perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorononanoic acid (PFNA) were detected in more than 95% of samples, with a median concentration of 0.5, 1.8, 4.1 and 0.4 ng/ml respectively. On the other hand, perfluorodecanoid (PFDA) were detected in 42,9% of participants, with a median concentration of 0.1 ng/ml. After the adjustment for some confounder variables, a positive association between PFDA and the presence of thyroid cancer was observed (OR= 1,96, P = 0.024) in subjects with measurable levels of PFDA. On the contrary, a negative association was found for PFHxS (OR= 0.31, P = 0.021).

Conclusions: This study shows, for the first time, a positive association between PFDA exposure and thyroid cancer, suggesting that it may be considered as a risk factor for TC development. On the contrary, an inverse correlation was found with PFHxS, as previously reported, likely due to a potential reverse causality.