Associations of Urinary Metabolites of Parabens and Bisphenol a with Premature Thelarche Among a Sample of Iranian Girls.

Endocrine-disrupting chemicals (EDC) may influence the process of puberty including the development of premature thelarche (PT). This study aimed to investigate the relation between exposure to bisphenol A (BPA) and parabens with PT among a sample of Iranian girls. This case-control study was conducted in 2022-2023 on girls with a mean (SD) age of 7.5(0.6) years in Isfahan, Iran. Participants were 90 newly diagnosed PT cases and 114 healthy controls. Spot urine samples were collected from both groups to measure the levels of BPA and paraben metabolites. We performed analyses of BPA and paraben metabolites including methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), and butylparaben (BuP) and benzylparaben (BzP) using gas chromatography-mass spectrometry. The association between concentrations of creatinine-standardized urinary bisphenol A and parabens and PT was analyzed with multiple logistic regression models, after adjusting for potential confounders. The results showed that individuals in the highest quartile of methyl paraben (OR=4.3, 95% CI:1.2-14.9, P=0.023), ethyl paraben (OR=4.7, 95% CI:1.3-17.2, P=0.018) and BPA (OR=5.03, 95% CI:1.4-17.9, P=0.013) had a significantly higher odds for PT compared to those in the lowest quartile. The findings of this study suggest that exposure to BPA, MeP and EtP is related to increased odds of early breast development in girls. Limiting the exposure to these chemicals may help to reduce the risk of precocious puberty.