Does bisphenol A reduce bioactive testosterone by disrupting androgen signaling and testicular steroidogenesis?

Bisphenol A (BPA) is a ubiquitous environmental chemical widely recognized as an endocrine-disrupting compound. Substantial evidence from molecular and animal models confirms that BPA directly interferes with the signaling and production of male sex hormones, specifically targeting the mechanisms that regulate testosterone synthesis.

Clinical and epidemiological findings

The impact of BPA on testosterone levels in human populations presents a complex and sometimes paradoxical picture.

• Total vs. Bioactive Testosterone: While animal models consistently show that BPA exposure reduces serum testosterone, human epidemiological studies often report a positive association between urinary BPA concentrations and total testosterone levels. However, recent evidence, including a 2024 meta-analysis, suggests that BPA exposure is associated with reduced levels of free (biologically active) testosterone.
• Role of SHBG: The apparent increase in total testosterone may be a compensatory response to BPA-induced elevations in Sex Hormone-Binding Globulin (SHBG). By increasing SHBG, BPA reduces the fraction of testosterone available to tissues, even if total circulating levels appear stable or elevated.
• Population Studies: Large-scale studies in the US and Italy have documented these complex hormonal shifts, highlighting that BPA exposure likely disrupts the androgenic balance rather than causing a simple, linear decline in total hormone volume.

Mechanistic explanations

BPA exerts its effects through several well-defined molecular pathways that disrupt both the production and the action of androgens.

• Steroid Receptor Interference: BPA acts as a competitive antagonist at the androgen receptor (AR). It binds to the ligand-binding domain, preventing natural androgens like dihydrotestosterone (DHT) from activating the receptor. Furthermore, BPA inhibits AR translocation to the nucleus by blocking its dissociation from the chaperone protein Hsp90.
• Impairment of Steroidogenesis: BPA disrupts the enzymatic pathway that converts cholesterol into testosterone. It specifically suppresses the expression of critical rate-limiting enzymes, including CYP11A1, 3β-HSD, and 17β-HSD.
• Mitochondrial and Epigenetic Damage: BPA induces the overproduction of reactive oxygen species (ROS), leading to mitochondrial dysfunction in Leydig cells (the primary site of testosterone production). It also triggers epigenetic modifications, such as the hypermethylation of the Sf1 promoter, which silences the transcriptional program required for steroidogenic enzyme synthesis.

Bottom line

BPA is a confirmed endocrine disruptor that impairs the machinery of testosterone production and blocks androgen receptor signaling. While human data on total testosterone levels are inconsistent, the evidence strongly suggests that BPA reduces the levels of bioactive free testosterone, potentially contributing to androgen deficiency in exposed men.