Menopause and lead body burden among US women aged 45–55, NHANES 1999–2010

Abstract

Background Environmental factors in menopause have received limited attention. Lead is a known reproductive toxicant associated with delayed puberty in girls that may also affect menopause. Methods The odds of menopause among US women aged 45–55 were estimated in the National Health and Nutrition Examination Survey, 1999–2010, in relation to quartiles of blood lead. Women still menstruating (n=2158) were compared to women with natural menopause (n=1063). Logistic regression models included age, race/ethnicity, current hormone use, poverty, smoking and where available, bone density or bone alkaline phosphatase. Results Lead levels (ug/dL) were higher in menopausal women, geometric mean (standard error) = 1.71 (0.04) vs. 1.23 (0.02). Adjusted odds of menopause and 95% confidence intervals for lead quartiles (lowest quartile referent) were 1.7 (1.0–2.8), 2.1 (1.2–3.6), and 4.2 (2.5–7.0) respectively. Results adjusting for bone markers were generally similar but had less precision. Conclusions Blood lead was associated with natural menopause in US women even after adjustment for bone turnover. This raises concern that lead exposure, even at low levels, may shorten women’s reproductive lifespan.

Sex-specific Profiles of Blood Metal Levels Associated with Metal–Iron Interactions

“…Our previous study [49] suggested that these paradoxical findings are probably due to the potential confounding effect of estrogen on blood lead levels. Several studies have shown that blood lead concentrations are higher in menopausal than in menstruating women, because lead may be mobilized from the skeleton during periods of increased bone demineralization, such as in menopause [57–62] . In addition, lower blood lead levels were observed in postmenopausal women receiving estrogen replacement therapy than in past or never users [63–65] .…”

“…This decrease during pregnancy may be mainly related to physiological factors, such as increases in plasma estrogen concentrations and their effect on lead redistribution. Thus, the decreasing effect of estrogen on blood lead is a major determinant of sex-specific differences in blood lead levels as a common thread relating menstrual, reproductive, and menopausal factors ( Table 2 ) [40,49,53,57,58,61,62,67–71,74,75] . However, age-related increase in blood lead is observed because of increase in exposure with age [67,74] .…”

Toenail metal concentrations and age at menopause

“…Previous research on associations with metal biomarkers in relation to age at menopause has been focused on exposure to lead, due to its established reproductive toxicity. 11 Prior studies have included an occupational cohort exposed to very high levels from smelting, 12 a cross-sectional examination of blood lead levels in National Health and Nutrition Examination Survey, 14 and a study of bone lead for which measurements were largely conducted after menopause. 13 These studies all concluded that higher biomarker levels of lead were related to an earlier age at menopause.…”

“… 12 Higher levels of lead measured in the bone were associated with earlier menopause in a subpopulation of the Nurses’ Health Study cohort 13 and similar associations were observed for blood lead in the National Health and Nutrition Examination Survey. 14 …”

Exposição ocupacional ao chumbo (Pb): efeitos sobre o estado redox celular e a influência de polimorfismos genéticos sobre a toxicocinética do metal

“…Portanto, os ossos (e em menor escala, os dentes) são os principais sítios de armazenamento do metal, chegando a constituir 90% de todo o Pb presente no organismo (GODWIN, 2001;FLORA et al, 2006;2012;MITRA et al, 2017). Sendo assim, mesmo após anos do término da exposição, o Pb pode ser deslocado do tecido ósseo para a corrente sanguínea, tanto por mecanismos fisiológicos, tais como a gravidez e a menopausa, quanto por patologias, como a osteoporose (MANTON et al, 2003;SCHNAAS et al, 2006;MENDOLA et al, 2013;MANOCHA et al, 2017).…”