Phthalate exposure linked to lower SHBG, higher risk for obesity in women
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Exposure to moderate or high levels of some phthalates is associated with lower levels of sex hormone-binding globulin and a higher risk for obesity among women, according to study data.
“Phthalates are harmful chemicals used as plasticizers in numerous products, including personal care items, cosmetics and cleaning supplies,” Alok Dwivedi, PhD, associate professor and director of the division of biostatistics and epidemiology in the department of molecular and translational medicine at Texas Tech University Health Sciences Center in El Paso, Texas, told Healio. “Using the [National Health and Nutrition Examination Survey] data sets, we observed that exposure to most phthalate metabolites is associated with low SHBG levels, which is a critical protein for maintaining sex hormones. As women are more likely to be exposed to phthalates, women should avoid the use of products containing harmful plasticizers and substances.”
Dwivedi and colleagues analyzed data from 2,004 reproductive and postmenopausal women who participated in NHANES from 2013 to 2016 (mean age, 46.6 years; 62.7% white, 14.7% Hispanic, 13.2% Black). Exposure to 13 phthalate metabolites was measured through urinary samples. Women were divided into tertiles for each phthalate compound based on concentration levels. Total testosterone, SHBG and BMI were acquired for all participants. Metabolic syndrome was defined as the presence of three or more abnormal cardiometabolic symptoms.
The findings were published in JAMA Network Open.
Of the study cohort, 11.8% had high total testosterone levels, 10.4% had low SHBG levels, 39.8% had obesity and 45.5% had metabolic syndrome.
No phthalates were associated with high testosterone levels. Women in the middle tertile of monocarboxyoctyl phthalate exposure had lower testosterone levels than those in the low tertile.
In adjusted analysis, women in both the middle and highest tertiles for monocarboxyoctyl phthalates, mono-n-butyl phthalates, mono(3-carboxypropyl) phthalates, monoethyl phthalates, mono-isobutyl phthalates and mono(2-ethyl-5-oxohexyl) phthalates; and those in the highest tertile of monocarboxynonyl phthalates, mono(2-ethyl-5-carboxypentyl) phthalates, mono(2-ethyl-5-hydroxyhexyl) phthalates and monobenzyl phthalates were more likely to have low SHBG levels compared with those in the lowest tertiles.
Women in the middle and highest tertiles for mono(2-ethyl-5-carboxypentyl) phthalates, mono-n-butyl phthalates, monoethyl phthalates and mono(2-ethyl-5-oxohexyl) phthalates had a higher risk for obesity than those in the lowest tertiles. There were no associations between phthalates and metabolic syndrome in adjusted data for the full cohort.
In an analysis of combined phthalate metabolites, women with a higher combined exposure to high molecular weight metabolites were more likely to have lower SHBG levels (beta = –0.09; 95% CI, –0.13 to –0.05) and a higher risk for obesity (RR = 1.12; 95% CI, 1.04-1.21).
The researchers noted that the associations between phthalates and SHBG, obesity and metabolic syndrome were different when the cohort was separated into premenopausal and postmenopausal groups.
“We observed that phthalate metabolites are associated with low SHBG levels, obesity, and metabolic syndrome to a greater extent among premenopausal women than postmenopausal women,” Dwivedi said. “Some phthalate metabolites and their composite exposures are more associated with obesity among postmenopausal women. This suggests that exposure to phthalates may have adverse effects in menopausal women as well. But we need to do more studies to understand how phthalate metabolites may affect clinical outcomes in different age groups.”
Dwivedi said the findings reveal that women with obesity or at high risk for cardiovascular disease need to be screened for phthalate exposure.
“Women with extremely low SHBG levels of less than 30 nmol/L may use guided treatments, including dietary and lifestyle modifications, as low SHBG levels can potentially lead to multiple disorders including polycystic ovary syndrome, CVD and cancer,” Dwivedi said. “Government authorities may develop feasible strategies and impose regulations and restrictions on the use of harmful and toxic phthalates in the products.”
For more information:
Alok Dwivedi, PhD, can be reached at alok.dwivedi@ttuhsc.edu.
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