Background: Parabens are chemical substances used as preservatives for their antibacterial and antifungal properties in many personal care products, and also sometimes in pharmaceutical and food products. Concerns for adverse human health effects arise from in vitro and in vivo studies showing endocrine disrupting effects, such as changes in the timing of puberty and alterations in reproductive hormones activity.Objective: To assess the associations between urinary levels of parabens and serum sex steroid hormones (estradiol and progesterone) and gonadotropins (follicle stimulating hormone [FSH] and luteinizing hormone [LH]) in girls and teens ages 6 to 17 years.Methods: We used data from the Canadian Health Measures Survey (2014-2015), and excluded participants taking medication influencing hormones and those who were pregnant. Methylparaben, ethylparaben, propylparaben, and butylparaben levels were measured in urine, summed, and standardized for creatinine. Hormones and parabens were natural-log-transformed and analyzed with multivariable linear regressions, adjusting for potential confounders (i.e., age, body mass index, sampling season, household income, and ethnicity).Results: The girls and teens included in the study (n=382) had a mean age of 11.0 years (standard deviation, 3.1), were white in majority (76%), and most had a normal BMI (73%). We observed significantly lower levels of hormones with higher paraben levels. A doubling in urinary parabens was associated with lower estradiol by 5.8% (95% CI -9.3, -2.1), lower FSH by 4.2% (95% CI -7.9, -0.3), and lower LH by 10.8% (95% CI -17.4, -3.7). Parabens were not associated with progesterone levels. Restricting the sample to girls who had not begun menstruation yielded similar results.Discussion: Similar to studies in animal models, we observed that exposure to parabens was associated with reduced levels of circulating reproductive hormones. These findings suggest that these compounds could alter the development and function of the reproductive system in girls and teens.