Association between metal exposure and Follicle Stimulating Hormone (FSH) and thyroid hormone among women of reproductive age: Korean Nationwide Biomonitoring Studies

BackgroundHeavy metals including mercury, lead, and cadmium are known as endocrine disrupting chemicals. There are few epidemiological studies available to present the relationship between metal exposures and changes in hormones. Infertility, polycystic syndrome, and uterine myoma are quite prevalent among women, which are related to hormonal abnormalities. In this study, we analyzed measurement data from nationwide biomonitoring studies in Korea and examine the association between co-exposure to heavy metals and sex and thyroid hormone among women of reproductive age. MethodsThis study involved 3,088 women of reproductive age (15-49 years) included in the 2th Korean National Environmental Health Survey in 2012-2014 and the 6th Korea National Health and Nutrition Examination Survey in 2013. The concentrations of mercury, lead, and cadmium in either urine or blood, serum follicle-stimulating hormone (FSH), thyroid stimulating hormone (TSH), triiodothyronine (T3), tetraiodothyronine (T4), and free tetraiodothyronine (FT4) were analyzed using multiple regression analysis. Age, body mass index, smoking status, alcohol, income, and urinary creatinine were adjusted in the statistical model. The statistical analysis was performed using R (ver. 3.6.3). ResultsMercury in urine was negatively associated with FSH [β (95% CI): -0.064 (-0.120, -0.008)]. Mercury in blood was positively associated with the FT4 [0.119 (0.030, 0.208)]. Lead in blood was positively associated with FSH [0.119 (0.030, 0.208)]. Cadmium had no significant association with any hormones. The results are comparable to other previous studies analyzing the association between single metal exposure and hormonal effects. Still, the effect (β) of metals seems greater in co-exposure models. Many the previous studies of the single exposure to heavy metals have reported that exposure to lead and cadmium increases FSH. For thyroid hormones, significant hormones or directions were different from the previous findings. ConclusionsFSH levels is related to infertility. Further studies of metals exposure are needed to protect the women of reproductive age.