Exposure to heavy metals and hormone levels in midlife women Original paper

What was studied?

This study examined the associations between urinary heavy metals, including arsenic, cadmium, mercury, and lead, and the levels of key sex hormones (estradiol, follicle-stimulating hormone, testosterone, and sex hormone-binding globulin) in midlife women. The research used data from the Study of Women’s Health Across the Nation (SWAN), a multi-ethnic cohort of women aged 45-56 years, followed over several years. The focus was on understanding how environmental exposures to heavy metals might influence hormone profiles during the menopausal transition, a critical period of reproductive aging, which can have long-term health implications for women, including cardiovascular disease, osteoporosis, and metabolic disorders.

Who was studied?

The study included 1,355 women from the SWAN cohort, representing a diverse range of racial and ethnic groups, including White, Black, Chinese, and Japanese women. Participants were aged 45-56 years at baseline (1999-2000). The analysis focused on midlife women who were followed through their menopausal transition, with hormone levels repeatedly measured up until 2017. Urinary metal concentrations were assessed at baseline, and serum hormone levels were measured annually. The cohort included women from different geographic locations across the U.S., providing insights into how environmental exposures affect sex hormone levels across various populations.

Most important findings

The study found that exposure to heavy metals significantly influenced hormone levels in midlife women. Specifically, a doubling in urinary mercury and lead concentrations was associated with lower estradiol (E2) levels by 2.2% and 3.6%, respectively. Additionally, higher lead concentrations were associated with higher follicle-stimulating hormone (FSH) levels, by 3.4%. Cadmium exposure was linked to increased levels of sex hormone-binding globulin (SHBG) by 3.6%. However, no significant association was found between metals and testosterone levels. The joint effects of metal mixtures showed a negative association with E2 and a positive association with FSH. The study also noted that the associations were stronger in early and late perimenopausal stages.

Key implications

The findings of this study highlight the significant role that environmental heavy metals can play in altering sex hormone levels during midlife, a crucial period for women’s health. The associations between higher lead and mercury concentrations with reduced estradiol levels and increased follicle-stimulating hormone levels suggest that metal exposure may accelerate ovarian aging, a factor that could impact menopause timing and related health risks, such as cardiovascular diseases and osteoporosis. The study emphasizes the need for public health strategies to minimize heavy metal exposure and further underscores the importance of monitoring environmental toxins as part of women’s healthcare during midlife.