Bisphenol A (BPA) is a synthetic phenolic compound first synthesized in the late 19th century and widely used since the mid-20th century to make polycarbonate plastics and epoxy resins. It is classified as an endocrine-disrupting chemical because it can bind to hormone receptors and modulate signaling pathways in laboratory and observational studies. BPA is not produced by the body; human contact typically comes from food packaging, canned-lining resins, thermal paper receipts, and other consumer products. In people, BPA is rapidly processed by Phase II pathways (mainly glucuronidation and sulfation) and eliminated in urine, so urinary measurements primarily reflect recent exposure and clearance rather than long-term body stores.

Elevated urinary BPA generally indicates recent or ongoing exposure to BPA-containing products or environments and higher internal burden at the time of sampling. In some studies, higher BPA exposure has been associated with changes in hormone signaling, metabolic markers, and stress-related pathways, but any single BPA result must be interpreted alongside hormone metabolites, cortisol timing, oxidative stress, and clinical context. Low or nondetectable BPA levels usually mean low recent exposure or effective metabolic clearance at the time the sample was collected. Low values do not rule out past or intermittent exposures and can be affected by timing of collection, individual metabolism, and laboratory limits of detection; interpretation is most meaningful when combined with the rest of the Hormone Zoomer panel.

BPA is included in the Hormone Zoomer to quantify recent environmental exposure to a common endocrine disruptor and to allow comparison with hormone metabolites, cortisol rhythms, oxidative stress, and bone markers. This helps providers see whether chemical burden aligns with shifts in hormone metabolism or stress signaling and supports more targeted, individualized evaluation.