Developmental exposure of mice to three ubiquitous endocrine-disrupting chemicals — bisphenol S (BPS), the brominated flame retardant BDE-47, and tetrabromobisphenol A (TBBPA) — from gestational day 8 through weaning permanently reprograms gene expression in the hypothalamic–pituitary (HP) axis of adult male offspring, with all three chemicals converging on G-protein-coupled-receptor (GPCR)-mediated intracellular signaling and immune pathways (Mogus et al., Environmental Pollution, 2024). That study measured transcriptomic changes only, in males only, at a single adult time point. The open problem is to determine the mechanistic basis and the physiological consequences of this convergence within the same exposure paradigm and chemical set: whether the shared pituitary and hypothalamic changes arise from a common upstream intracellular signaling event engaged by chemically dissimilar disruptors rather than from chemical-specific receptor pathways; whether the transcriptional changes reach the protein and hormone level and alter pituitary output, circulating hormones and HP feedback in the adult animal; and to what extent they are direct actions of the chemicals on HP-axis tissues rather than secondary compensatory responses to altered peripheral (gonadal, thyroid, hepatic) feedback during development. No published work has resolved these questions for this model or chemical set. Same-paradigm studies have already characterized adult metabolic, hepatic, adipose, microbiome, body-weight and behavioral endpoints for BDE-47 or for all three chemicals (Khalil et al., 2017, 2018; Abrha and Suvorov, 2018; Kim et al., 2015; Gomez et al., 2021) and pre-pubertal female reproductive-tract estrogen responsiveness for BPS (Hill et al., 2017); pituitary protein and hormone output, HP-axis feedback integrity, and the direct-versus-compensatory question remain unaddressed.

Background

Endocrine-disrupting chemicals (EDCs) are exogenous substances that interfere with hormonal signaling; humans are exposed continuously to mixtures of them through plastics, food, dust, and consumer products. Animal studies have repeatedly shown that exposure during critical windows of development — in utero and during lactation — can permanently alter endocrine health, a phenomenon often called developmental programming. Almost all of this experimental work has addressed the hormone-producing peripheral glands (gonads, thyroid, adrenals) and circulating hormone levels. Far less is known about the central level of endocrine control: the hypothalamic–pituitary (HP) axis, in which hypothalamic neurons release peptide signals (for example gonadotropin-releasing hormone, corticotropin-releasing hormone, growth-hormone-releasing hormone, somatostatin) that govern the pituitary's secretion of tropic hormones (luteinizing hormone, LH, and follicle-stimulating hormone, FSH, for the gonadal axis; adrenocorticotropic hormone, ACTH, for the adrenal axis; thyroid-stimulating hormone, TSH, for the thyroid axis; growth hormone, GH, for the liver/somatotropic axis), which in turn regulate the peripheral glands and receive feedback from circulating hormones.

The source study (Mogus, Marin, Arowolo, Salemme and Suvorov, posted on bioRxiv in January 2024 and published in Environmental Pollution in 2024) asked whether common EDCs can permanently reprogram this central control level. Pregnant CD-1 mice (a standard outbred laboratory strain) received, once daily from gestational day 8 through lactation day 21 (weaning), one of three structurally unrelated pollutants: bisphenol S (BPS, a bisphenol-A replacement used in plastics and thermal paper), 2,2',4,4'-tetrabromodiphenyl ether (BDE-47, a polybrominated diphenyl ether flame retardant), or 3,3',5,5'-tetrabromobisphenol A (TBBPA, the highest-volume brominated flame retardant), each delivered at 0.2 mg/kg body weight/day (0.2 mg/mL solutions given at 1 µL/g body weight). Male offspring were left untreated until postnatal day 140 (PND140, young adulthood), when whole pituitaries were profiled by RNA sequencing (RNA-seq, which quantifies all transcripts genome-wide) and selected hypothalamic genes by RT-qPCR (a targeted quantitative assay for individual transcripts). All three chemicals induced long-lasting, mostly suppressive changes in pituitary genes governing endocrine function: HP-gonad and HP-liver (growth) axes were affected by all three, BPS specifically affected the HP-adrenal axis and BDE-47 the HP-thyroid axis, immune-related genes were reduced by all three, and — notably — all three converged on genes of GPCR-mediated intracellular signaling (G protein-coupled receptors are cell-surface receptors whose intracellular cascades, involving signalers such as RASD1 and DUSP1 and transcription factors such as FOS, JUNB and EGR1, are shared downstream of many hormone receptors), suggesting a common point of chemical convergence.

Prior and adjacent work frames why the observation matters but also what it leaves open. Perinatal bisphenol A exposure was earlier shown to alter hypothalamic–pituitary–gonadal axis gene expression in CD-1 mice (Xi et al., 2011), and the CLARITY-BPA consortium (a multi-institution United States research program on bisphenol A toxicity) reported both gene-expression and DNA-methylation changes in the hypothalamus of adult rats developmentally exposed to BPA or ethinyl estradiol (Cheong et al., 2018), indicating that developmental EDC exposure can leave epigenetic marks in neuroendocrine tissue. In rats, prenatal exposure to a human-relevant EDC mixture (NeuroMix) produced physiological and behavioral phenotypes (Topper et al., 2019) and sex- and tissue-specific transcriptomic changes across the HPG axis in the same animals (Milewski et al., 2025), and perinatal BPS alters hypothalamic kisspeptin (a key reproductive neuropeptide) signaling and sexual behavior in both male and female mice (Bonaldo et al., 2025). None of these, however, establishes for the BPS/BDE-47/TBBPA mouse model what the reprogramming means: the source study itself measured no protein levels, no pituitary hormones, and no functional endocrine endpoints, examined only males (females were excluded because endocrine gene expression in females varies with the estrous cycle), sampled only one adult time point, used a single dose, and could not distinguish a direct reprogramming of HP-axis cells from indirect adaptation to developmentally altered peripheral hormone feedback.

Problem Statement

In the mouse developmental-exposure model of Mogus et al. (CD-1 mice exposed developmentally — gestational day 8 through weaning — to BPS, BDE-47, or TBBPA at 0.2 mg/kg body weight/day, offspring analyzed in adulthood), the persistent reprogramming of hypothalamic–pituitary gene expression is established at the transcript level only. Determine the mechanistic basis and the physiological consequences of this convergence within this exposure paradigm and chemical set, specifically: (i) the mechanism of convergence — whether the shared pituitary and hypothalamic changes arise from a common upstream intracellular signaling event engaged by chemically dissimilar disruptors (for example GPCR-linked intracellular cascades in pituitary cells, such as cAMP–PKA–CREB or MAPK–ERK signaling, or a shared inflammatory/immune trigger) rather than from chemical-specific receptor pathways; (ii) whether these transcriptional changes reach the protein and hormone level and alter pituitary output and HP feedback in the adult animal — pituitary hormone content and secretion (LH, TSH, GH), circulating gonadal, thyroid and IGF-1 (insulin-like growth factor 1, the growth-hormone mediator) hormones, ACTH/corticosterone, and the integrity of negative feedback along those axes, together with the functional consequences that the source could only infer (it reasons that reduced Lhb expression, and potentially reduced LH protein, would imply low testicular steroidogenesis, decreased testosterone and an altered rate of spermiogenesis) and the field gap it names, namely how the pituitary and hypothalamus respond to developmental EDC exposures "and how these changes may affect HP feedback functions"; (iii) the extent to which the observed pituitary and hypothalamic changes are direct actions of the chemicals on those tissues or secondary compensatory responses to altered peripheral feedback during development — the source offers both readings for its own data without resolving them (BDE-47 "may have some direct effect on pituitary Gnrhr expression specifically, or by altering feedback sensitivity to gonadal steroids"; the thyroid-axis changes may reflect "compensatory changes during development when the axis was overstimulated"; the HP-liver axis is read against a published "long term increase in IGF-1 plasma levels" after developmental BDE-47); and (iv) an optional generalizability assessment of whether the converging signaling and immune genes qualify as candidate shared targets of EDC action on the HP axis, where a gene qualifies only if it is reported differentially expressed in the source study and in at least one independent published EDC transcriptomic dataset (for example the HPG-axis dataset of Milewski et al. 2025 or the hypothalamic dataset of Cheong et al. 2018), and whether the pituitary is a point of disrupting convergence that merits further attention, the source naming the HP-gonad and HP-liver axes as "priority targets for future EDC study" and stating that the shared pituitary immune responses "warrant further investigation". Sub-questions (i)–(iii) are the scientific questions this problem poses; (iv) is a secondary question the problem does not require. Because the source study supplies transcript-level measurements only, each of (i)–(iii) rests on an evidence-based assessment drawn from the source data and the published literature.

This problem concerns the mechanism and the consequences of the established expression phenotype within the source paradigm, not a re-description of that phenotype. Female offspring were excluded from the source study because endocrine gene expression in females may be affected by the estrous cycle; extending the analysis to female offspring is an optional extension of the problem, and the problem does not additionally require an epigenetic account of persistence or a multi-dose characterization of the exposure.

References

  1. Mogus JP, Marin M, Arowolo O, Salemme V, Suvorov A. Developmental Reprogramming of Hypothalamic-Pituitary Axis in Mice by Common Environmental Pollutants. bioRxiv preprint, posted 2024-01-05. DOI 10.1101/2024.01.04.574224. https://doi.org/10.1101/2024.01.04.574224
  2. Mogus JP, Marin M, Arowolo O, Salemme V, Suvorov A. Developmental exposures to common environmental pollutants result in long-term Reprogramming of hypothalamic-pituitary axis in mice. Environmental Pollution 2024;361:124890. DOI 10.1016/j.envpol.2024.124890. https://doi.org/10.1016/j.envpol.2024.124890
  3. Milewski TM, Streifer M, Thompson LM, Sheinhaus D, Hynes A, Gore AC. Transcriptomic Changes Across the HPG Axis Following Prenatal Exposure to the EDC Mixture NeuroMix. Endocrinology 2025;166(10):bqaf135. DOI 10.1210/endocr/bqaf135. https://doi.org/10.1210/endocr/bqaf135
  4. Topper VY, Reilly MP, Wagner LM, Thompson LM, Gillette R, Crews D, Gore AC. Social and neuromolecular phenotypes are programmed by prenatal exposures to endocrine-disrupting chemicals. Molecular and Cellular Endocrinology 2019;479:133-146. DOI 10.1016/j.mce.2018.09.010. https://doi.org/10.1016/j.mce.2018.09.010
  5. Bonaldo B, Casile A, Bettarelli M, Marraudino M, Gotti S. Perinatal exposure to bisphenol A or S alters differently sexual behavior and kisspeptin system in mice. Environmental Research 2025;269:120888. DOI 10.1016/j.envres.2025.120888. https://doi.org/10.1016/j.envres.2025.120888
  6. Stub M, Ramhøj L, Axelstad M, Pedersen M, Svingen T. Effects of perfluorooctane sulfonate (PFOS) and tetrabromobisphenol A (TBBPA) on reproductive development in rats. Reproductive Toxicology 2026;140:109170. DOI 10.1016/j.reprotox.2026.109170. https://doi.org/10.1016/j.reprotox.2026.109170
  7. Kim B, Colon E, Chawla S, Vandenberg LN, Suvorov A. Endocrine disruptors alter social behaviors and indirectly influence social hierarchies via changes in body weight. Environmental Health 2015;14:64. DOI 10.1186/s12940-015-0051-6. https://doi.org/10.1186/s12940-015-0051-6
  8. Gomez MV, Dutta M, Suvorov A, Shi X, Gu H, Mani S, Yue CJ. Early Life Exposure to Environmental Contaminants (BDE-47, TBBPA, and BPS) Produced Persistent Alterations in Fecal Microbiome in Adult Male Mice. Toxicological Sciences 2021;179(1):14-30. DOI 10.1093/toxsci/kfaa161. https://doi.org/10.1093/toxsci/kfaa161
  9. Cheong A, Johnson SA, Howald EC, Ellersieck MR, Camacho L, Lewis SM, Vanlandingham MM, Ying J, Ho SM, Rosenfeld CS. Gene expression and DNA methylation changes in the hypothalamus and hippocampus of adult rats developmentally exposed to bisphenol A or ethinyl estradiol: a CLARITY-BPA consortium study. Epigenetics 2018;13(7):704-720. DOI 10.1080/15592294.2018.1497388. https://doi.org/10.1080/15592294.2018.1497388
  10. Xi W, Lee CKF, Yeung WSB, Giesy JP, Wong MH, Zhang X, Hecker M, Wong CKC. Effect of perinatal and postnatal bisphenol A exposure to the regulatory circuits at the hypothalamus–pituitary–gonadal axis of CD-1 mice. Reproductive Toxicology 2011;31(4):409-417. DOI 10.1016/j.reprotox.2010.12.002. https://doi.org/10.1016/j.reprotox.2010.12.002
  11. Gherman-Lencu CC, Alexescu TG, Mureșanu C, Gerdanovics CA, Milaciu MV, Iancu DM. Implications of Endocrine-Disrupting Chemicals for Human Health and Effective Methods for Prevention and Reduction. Toxics 2026;14(6):515. DOI 10.3390/toxics14060515. https://doi.org/10.3390/toxics14060515
  12. Khalil A, Parker M, Mpanga R, Cevik SE, Thorburn C, Suvorov A. Developmental Exposure to 2,2',4,4'-Tetrabromodiphenyl Ether Induces Long-Lasting Changes in Liver Metabolism in Male Mice. Journal of the Endocrine Society 2017;1(4):323-344. DOI 10.1210/js.2016-1011. https://doi.org/10.1210/js.2016-1011
  13. Khalil A, Cevik SE, Hung S, Kolla S, Roy MA, Suvorov A. Developmental Exposure to 2,2',4,4'-Tetrabromodiphenyl Ether Permanently Alters Blood-Liver Balance of Lipids in Male Mice. Frontiers in Endocrinology 2018;9:548. DOI 10.3389/fendo.2018.00548. https://doi.org/10.3389/fendo.2018.00548
  14. Abrha A, Suvorov A. Transcriptomic Analysis of Gonadal Adipose Tissue in Male Mice Exposed Perinatally to 2,2',4,4'-Tetrabromodiphenyl Ether (BDE-47). Toxics 2018;6(2):21. DOI 10.3390/toxics6020021. https://doi.org/10.3390/toxics6020021
  15. Hill CE, Sapouckey SA, Suvorov A, Vandenberg LN. Developmental exposures to bisphenol S, a BPA replacement, alter estrogen-responsiveness of the female reproductive tract: a pilot study. Cogent Medicine 2017;4(1):1317690. DOI 10.1080/2331205x.2017.1317690. https://doi.org/10.1080/2331205x.2017.1317690