Urinary bisphenol A versus serum bisphenol A concentration and ovarian reproductive outcomes among IVF patients: Which is a better biomarker of BPA exposure?
Molecular and Cellular Toxicology
© 2017, The Korean Society of Toxicogenomics and Toxicoproteomics and Springer Science+Business Media B.V., part of Springer Nature. Bisphenol A (BPA) is an endocrine-disrupting compound (EDC) that is used widely in commercial products in the production of polycarbonate plastics for baby and water bottles, epoxy resins for lacquer lining of food and beverage cans and water pipes, dental sealants, dental composites and thermal receipts paper. There is inhibitory effect of BPA on nuclear estrogen (E2) production in granulosa cells of developing follicles that disrupt normal development to the antral follicles via suppression of E2 in granulosa cells of developing follicles during the menstrual cycle followed by reduction in the number of oocytes retrieved in in-vitro fertilization (IVF) patients. Several studies corroborate an inverse association between serum and/or urinary BPA concentration and the IVF outcome: Peak E2 levels and the number of oocytes retrieved. Upon oral ingestion, 99.5% of unconjugated parent BPA (free BPA) is metabolized to either BPA glucuronide (BPA-G) or BPA sulfate (BPA-S). The unconjugated BPA can bind to the estrogen receptors (ER) while conjugated BPA (biologically inactive BPA) do not bind the estrogen receptor (ER). The challenge is to assess the relationship between BPA exposure among infertile patients with respect to follicular response and health during IVF. The establishment of temporal sequence between BPA exposure and infertility would be the research question to answer: Which route is a better biomarker? The advantages of urine BPA collection would provide pragmatic advantages for clinicians in order to practice cost-effective medicine. However, unconjugated BPA measurement (compared to total BPA) introduces challenges in measurement accuracy since unconjugated BPA requires higher magnitude of limit of detection (LOD) with higher risk of contamination from the medical equipment. The difference in route of BPA assessment could introduce bias in the interpretation of results in terms of the association between BPA levels and the number of oocytes. Fujimoto et al. and Bloom et al. analyzed the relationship between serum BPA and IVF outcome in infertile women. It may sound hypothetically justified due to utilizing serum unconjugated BPA, this strategy is not successful in choosing a practical biomarker of BPA exposure due to toxicokinetic properties of BPA metabolism and excretion in humans.