Associations Between Repeated Measures of Urinary Phthalate Metabolites With Hormones and Timing of Natural Menopause

Abstract

Phthalates, ubiquitous endocrine-disrupting chemicals, may impact ovarian folliculogenesis and steroidogenesis. We examined the associations of urinary phthalate metabolites with hormones including estradiol, testosterone, follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), and anti-Müllerian hormone (AMH), and timing of natural menopause in midlife women. Data were from 1,189 multi-racial/ethnic women aged 45-56 years without hormone therapy from the Study of Women’s Health Across the Nation (SWAN). Urinary concentrations of 12 phthalate metabolites and hormones were repeatedly measured in 1999-2000 and 2002-2003, resulting in a total of 2,111 observations. Linear mixed-effect models were used to calculate percent differences (%D) and 95% confidence intervals (95% CIs) in serum concentrations of estradiol, testosterone, FSH, SHBG, and AMH. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% CIs of natural menopause. We observed significant associations of phthalate metabolites with lower testosterone concentrations: MCOP with testosterone (%D: -2.08%, 95% CI: -3.66, -0.47), and MnBP with testosterone (%D: -1.99%, 95% CI: -3.82, -0.13), after adjusting for multiple comparisons with false discovery rates<5%. Lower AMH concentrations were also found with higher MECPP (%D: -14.26%, 95% CI: -24.10, -3.14), MEHHP (%D: -15.58%, 95% CI: -24.59, -5.50), and MEOHP (%D: -13.50%, 95% CI: -22.93, -2.90). No associations were observed for other hormones or timing of natural menopause. These results suggest that exposure to phthalates may affect circulating levels of testosterone and diminish the ovarian reserve in midlife women. Given the widespread exposure, reduced exposure to phthalates may be a key step to prevent reproductive effects of phthalates.