Synthetic Phenolic Antioxidants and Their Metabolites in Follicular Fluid and Association with Diminished Ovarian Reserve: A Case-Control Study

Background: Diminished/decreased ovarian reserve (DOR) is a disorder of ovarian function, which severely affects women's reproductive health. Accumulating evidence has found that adverse environmental factors can affect ovarian function. However, whether synthetic phenolic antioxidants (SPAs) exposure is associated with DOR is still unknown.

Objectives: We explored whether concentrations of SPAs and their metabolites are associated with DOR.

Methods: A case-control study was conducted from January 2019 to January 2020 in China. One hundred eighty-one women 20-44 years of age, with (case group, $n=63$) and without DOR (control group, $n=118$) were included in our study. The follicular fluid concentrations of typical SPAs and their metabolites were measured, including butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), butylated hydroxytoluene (BHT), and five BHT metabolites [3,5-di-tert-butyl-4-hydroxy-benzylalcohol (BHT-OH), 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO), 3,5-di-tert-butyl-4-hydroxybenzoic acid (BHT-COOH), 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q), and 2,6-di-tert-butyl-4-hydroxy-4-methylcyclohexa-2,5-dien-1-one (BHT-quinol)]. Information about serum basal concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and anti-Müllerian hormone (AMH) and the basal antral follicle count (AFC) was collected.

Results: The measured frequencies of BHA, TBHQ, BHT, BHT-OH, BHT-CHO, BHT-COOH, BHT-Q, and BHT-quinol in follicular fluid were 1.7%, 2.2%, 40.3%, 46.4%, 57.5%, 100%, 64.6%, and 49.2%, respectively. The concentrations of BHT-CHO ( $0.49\text{ng}/\mathrm{mL}$ vs. $0.12\text{ng}/\mathrm{mL}$, $p=0.041$), BHT-COOH ( $0.45\text{ng}/\mathrm{mL}$ vs. $0.28\text{ng}/\mathrm{mL}$, $p<0.001$), BHT-Q ( $0.70\text{ng}/\mathrm{mL}$ vs. $0.13\text{ng}/\mathrm{mL}$, $p<0.001$), and the sum of five BHT metabolites ( $\Sigma 5\text{metabolites}$; $1.79\text{ng}/\mathrm{mL}$ vs. $1.0\text{ng}/\mathrm{mL}$, $p<0.001$) in the case group were significantly higher than those in the control group. The risk of DOR was further analyzed according to the tertiles of chemical concentration. Compared with the low levels of BHT metabolites, the adjusted odds ratios (ORs) for DOR were significantly increased in the high levels of BHT-CHO [ $\text{OR}=3.19$, 95% confidence interval (CI): 1.22, 8.31, $p=0.018$], BHT-COOH [ $\text{OR}=4.73$ (95% CI: 1.63, 13.71), $p=0.004$], and BHT-Q [ $\text{OR}=4.48$ (95% CI: 1.69, 11.86), $p=0.003$] after adjusting for age, body mass index, education, infertility type, triglycerides, and total Cholesterol. Moreover, compared with the low level of $\Sigma 5\text{metabolites}$, increased adjusted ORs for DOR were found both in the middle level [ $\text{OR}=4.11$ (95% CI: 1.44, 11.75), $p=0.008$] and high level [ $\text{OR}=5.51$ (95% CI: 1.81, 16.77), $p=0.003$], showing an obvious dose-response relationship ( $p_{\text{Trend}}=0.003$).

Conclusion: In this study, we report the measured frequency and concentrations of BHA, TBHQ, BHT, and their metabolites in follicular fluid. Moreover, we found the concentrations of BHT metabolites, especially BHT-CHO, BHT-COOH, and BHT-Q, are positively associated with the increased risk of DOR. https://doi.org/10.1289/EHP11309.