CHICAGO, IL – Male rats exposed to di-(2-ethylhexyl) phthalate (DEHP), a ubiquitous plasticizer found in numerous consumer products, during critical early developmental stages exhibited significantly higher levels of anxiety in adulthood. These findings, presented at ENDO 2026, the Endocrine Society’s annual scientific meeting held in Chicago, Illinois, raise concerns about the potential long-term behavioral impacts of endocrine-disrupting chemicals (EDCs) on human development.
The research, conducted by a team from the University of Buenos Aires School of Medicine, highlights a critical window of vulnerability during prenatal and immediate postnatal development. "This research demonstrates that one of the most widely used plasticizers worldwide is capable of causing behavioral changes when the subject is exposed during the prenatal and immediate postnatal developmental stages, with this effect lasting over time," stated Osvaldo Juan Ponzo, M.D., Ph.D., a professor of physiology at the University of Buenos Aires School of Medicine and a lead investigator on the study. While acknowledging the study’s focus on rodents, Dr. Ponzo emphasized the suggestive implications for human health.
Unpacking the Chemical: DEHP and Its Pervasiveness
DEHP is a phthalate ester, a class of chemicals widely employed as plasticizers to impart flexibility, durability, and longevity to plastics. Its widespread use means it is integrated into a vast array of everyday items, underscoring the potential for broad human exposure. The chemical is a common additive in medical devices such as intravenous tubing and blood bags, children’s toys, shower curtains, flooring, and various packaging materials. Its presence in such diverse applications makes it a significant component of the modern material landscape.
Previous scientific investigations have established DEHP and its metabolic byproducts as substances capable of interfering with the endocrine system, impacting multiple organ systems in both animal models and humans. Of particular concern are its documented effects on the reproductive and nervous systems. Building upon this existing body of knowledge, the University of Buenos Aires researchers specifically aimed to explore DEHP’s influence on anxiety-related behaviors in adult male rats. Their investigation also sought to elucidate the potential roles of gamma-aminobutyric acid (GABA), a crucial inhibitory neurotransmitter in the central nervous system, and testosterone, a key sex hormone, in mediating these observed behavioral changes.
The Experimental Design: Tracing Anxiety from Development to Adulthood
The study commenced with the administration of DEHP to pregnant female rats. Commencing on the first day of gestation, the rodents received daily oral doses of the plasticizer, a regimen that continued uninterrupted until their offspring were weaned. This approach ensured that the developing fetuses and neonates were exposed to DEHP during critical periods of neurodevelopment and hormonal differentiation.
The male offspring were then monitored until they reached adulthood, a stage defined in the study as 70 days of age. At this point, the researchers employed a well-established behavioral paradigm known as the elevated plus maze (EPM) to assess anxiety-related behaviors. The EPM leverages rodents’ innate aversion to open, elevated spaces. The maze is constructed in the shape of a plus sign, featuring four arms: two enclosed arms providing a sense of security and two open arms extending into the surrounding environment.
During their exploration of the maze, the rats’ behavior was meticulously recorded and analyzed. Key metrics included the frequency of entries into both open and enclosed arms, the duration of time spent in each type of arm, and the extent of "freezing" behavior – a state of immobility often indicative of fear or anxiety. Rats exhibiting higher levels of anxiety are typically expected to spend more time in the enclosed, safer arms and less time exploring the open, potentially threatening areas, along with increased freezing durations.
Reversing the Tide: The Protective Roles of GABA and Testosterone
The findings from the EPM test revealed a clear pattern among the DEHP-exposed adult male rats. These animals displayed significant indicators of heightened anxiety when compared to a control group that had not been exposed to the chemical. Specifically, the DEHP-exposed rats demonstrated a marked reluctance to explore the open arms of the maze, spent a greater proportion of their time within the enclosed arms, and exhibited significantly longer periods of freezing behavior. These observations align with established behavioral correlates of anxiety in rodent models.
Crucially, the researchers investigated whether the administration of GABA agonists or testosterone could mitigate these anxiety-inducing effects. Ninety minutes prior to being placed in the EPM, a subset of the DEHP-exposed rats received treatments. One group was administered GABA agonists, molecules designed to bind to and activate GABA receptors, thereby enhancing the inhibitory effects of this neurotransmitter. Another group was treated with testosterone, administered every 48 hours for a period of 14 days preceding the behavioral testing.
The results of these intervention trials were striking. DEHP-exposed rats that received either GABA agonists or testosterone exhibited a reversal of the anxious behaviors observed in the untreated DEHP group. These treated animals showed a greater propensity to explore the open arms of the maze, spent less time in the enclosed arms, and displayed reduced freezing behavior. This suggests that both GABAergic signaling and testosterone can play a protective or modulatory role against the anxiety-promoting effects of early-life DEHP exposure.
"This work demonstrates that contact with DEHP in the early stages of life could modify behavior with regard to anxiety, even in the absence of DEHP exposure in adulthood," Dr. Ponzo reiterated. "These neuroendocrine changes can be reversed by treating with GABA agonists or testosterone." This finding is particularly significant as it indicates that developmental exposures can have lasting effects that are not simply a result of ongoing chemical presence.
Broader Context: Endocrine Disruptors and Neurodevelopmental Pathways
The research presented at ENDO 2026 adds to a growing body of scientific literature linking endocrine-disrupting chemicals to a range of adverse health outcomes, including neurodevelopmental and behavioral disorders. EDCs are exogenous substances or mixtures that alter the function of the endocrine system and consequently cause adverse health effects in an intact organism, or its progeny, or (sub)populations. The endocrine system is a complex network of glands and hormones that regulate numerous bodily functions, including growth, metabolism, mood, and reproduction.
The timing of exposure to EDCs is a critical factor. During prenatal and early postnatal development, organ systems, including the brain, are undergoing rapid and sensitive differentiation. Exposures during these windows can lead to permanent alterations in structure and function, with consequences that may not become apparent until later in life. DEHP, by its nature as a plasticizer, is not chemically bound to the plastic matrix and can leach out over time, especially when exposed to heat or fatty substances, increasing the potential for human exposure.
The identified roles of GABA and testosterone in the study are particularly relevant. GABA is the primary inhibitory neurotransmitter in the mammalian brain, playing a vital role in regulating neuronal excitability and maintaining a balance between excitation and inhibition. Disruptions in GABAergic signaling have been implicated in anxiety disorders, epilepsy, and other neurological conditions. Testosterone, a potent androgen, not only influences male sexual development and reproduction but also has significant effects on brain development and function, including its influence on mood and behavior. The study suggests that DEHP exposure may disrupt the delicate interplay between these crucial neuroendocrine systems.
Implications and Future Directions
The implications of this research extend beyond rodent models. While direct extrapolation to humans requires further investigation, the fundamental biological pathways involved are conserved across mammalian species. The widespread presence of DEHP in the environment and consumer products means that human populations, particularly vulnerable groups such as pregnant women and children, are routinely exposed.
The findings underscore the importance of continued research into the long-term neurobehavioral effects of EDCs. Understanding the specific mechanisms by which these chemicals impact brain development and function is crucial for developing effective strategies to mitigate risks. This includes not only identifying specific chemicals of concern but also understanding the critical windows of exposure and the dose-response relationships.
Regulatory bodies worldwide are increasingly scrutinizing the use of phthalates, including DEHP, due to concerns about their potential health effects. Studies like this provide valuable scientific evidence to inform these regulatory decisions and to guide public health policies aimed at protecting populations from harmful exposures. The ability to reverse DEHP-induced anxiety through interventions targeting GABA and testosterone also opens avenues for potential therapeutic strategies, although such applications would require extensive further research and clinical trials.
The Endocrine Society, as a leading global organization for endocrinology, provides a platform like its annual meeting for the dissemination of cutting-edge research. Presentations at ENDO 2026 offer a glimpse into the evolving scientific understanding of hormone-related health issues, from basic science discoveries to clinical applications and public health implications. The ongoing dialogue and collaboration fostered at such meetings are essential for advancing scientific knowledge and addressing complex health challenges posed by environmental factors.
In conclusion, the research presented at ENDO 2026 provides compelling evidence that early life exposure to DEHP can induce lasting anxiety-like behaviors in male rats, mediated in part by disruptions in GABA and testosterone pathways. This study reinforces the need for vigilance regarding the pervasive presence of endocrine-disrupting chemicals in our environment and highlights the critical importance of protecting developmental windows from chemical insults to safeguard long-term neurobehavioral health. Further research is warranted to fully elucidate the human health implications and to inform robust public health interventions.
