Associations of pharmaceutical and personal care product chemical exposure with thyroid nodules and thyroid homeostasis

Pharmaceuticals and personal care products (PPCPs) have been considered as potential contributors to thyroid nodule (TN) and abnormal thyroid homeostasis, but epidemiological evidence is scarce. A total of 1261 individuals comprised of 367 TN patients and 895 controls were recruited from Sichuan, China. The urinary concentrations of fourteen PPCPs were measured. Five thyroid hormones (THs) in serum were determined as indicators of thyroid homeostasis, including thyroid-stimulating hormone, triiodothyronine (T3), thyroxine (T4), free-T3 and free-T4. Serum levels of thyroglobulin antibody (TGAb) and thyroperoxidase antibody (TPOAb) were quantified to identify individual thyroid antibody (TA) statuses. TN patients exhibited higher propyl-paraben (PrP) (median: 1.30 µg/g Cr) level than controls (0.64 µg/g Cr). PrP were significantly associated with TN risk with ORs of 1.060 (95 % CI: 1.002, 1.122). The relationship of methyl-paraben with TN risk was nonlinear (p = 0.049). PPCP exposure was significant with TN risk only in females and TA positive (TPOAb or TGAb) groups, indicating that PPCP susceptibility to TN differs by sex and TA status. Linear regression models showed ethyl-paraben was significantly negatively associated with T4 (β: -0.005, 95 % CI: -0.011, -0.002) and T3 (β: -0.007, 95 % CI: -0.015, -0.002), and positively associated with TPOAb (β: 0.059, 95 % CI: 0.000, 0.119), suggesting that certain PPCP exposure could affect thyroid homeostasis and autoimmunity. The effects of PPCP exposure on TH and TA levels presented sex-specific. Our findings suggest that PPCP exposure increases TN risk and affects thyroid homeostasis, exhibiting sex and antibody status dependence.