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An endocrine-disrupting chemical (EDC) is an exogenous chemical, or mixture of chemicals, that can interfere with any aspect of hormone action. The potential for deleterious effects of EDC must be considered relative to the regulation of hormone synthesis, secretion, and actions and the variability in regulation of these events across the life cycle. The developmental age at which EDC exposures occur is a critical consideration in understanding their effects. Because endocrine systems exhibit tissue-, cell-, and receptor-specific actions during the life cycle, EDC can produce complex, mosaic effects. This complexity causes difficulty when a static approach to toxicity through endocrine mechanisms driven by rigid guidelines is used to identify EDC and manage risk to human and wildlife populations. We propose that principles taken from fundamental endocrinology be employed to identify EDC and manage their risk to exposed populations. We emphasize the importance of developmental stage and, in particular, the realization that exposure to a presumptive "safe" dose of chemical may impact a life stage when there is normally no endogenous hormone exposure, thereby underscoring the potential for very low-dose EDC exposures to have potent and irreversible effects. Finally, with regard to the current program designed to detect putative EDC, namely, the Endocrine Disruptor Screening Program, we offer recommendations for strengthening this program through the incorporation of basic endocrine principles to promote further understanding of complex EDC effects, especially due to developmental exposures.

In 1997, the first in vivo bisphenol A (BPA) study by endocrinologists reported that feeding BPA to pregnant mice induced adverse reproductive effects in male offspring at the low dose of 2 µg/kg/day. Since then, thousands of studies have reported adverse effects in animals administered low doses of BPA. Despite more than 100 epidemiological studies suggesting associations between BPA and disease/dysfunction also reported in animal studies, regulatory agencies continue to assert that BPA exposures are safe. To address this disagreement, the CLARITY-BPA study was designed to evaluate traditional endpoints of toxicity and modern hypothesis-driven, disease-relevant outcomes in the same set of animals. A wide range of adverse effects was reported in both the toxicity and the mechanistic endpoints at the lowest dose tested (2.5 µg/kg/day), leading independent experts to call for the lowest observed adverse effect level (LOAEL) to be dropped 20 000-fold from the current outdated LOAEL of 50 000 µg/kg/day. Despite criticism by members of the Endocrine Society that the Food and Drug Administration (FDA)'s assumptions violate basic principles of endocrinology, the FDA rejected all low-dose data as not biologically plausible. Their decisions rely on 4 incorrect assumptions: dose responses must be monotonic, there exists a threshold below which there are no effects, both sexes must respond similarly, and only toxicological guideline studies are valid. This review details more than 20 years of BPA studies and addresses the divide that exists between regulatory approaches and endocrine science. Ultimately, CLARITY-BPA has shed light on why traditional methods of evaluating toxicity are insufficient to evaluate endocrine disrupting chemicals., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Exposure of mammalian fetuses to endocrine disruptors can increase the risk of adult-onset diseases. We previously showed that exposure of mouse fetuses to bisphenol A (BPA) caused adult-onset obesity. To examine roles of epigenetic changes in this delayed toxicity, we determined the effects of fetal mouse exposure to BPA on genome-wide DNA methylation and messenger RNA (mRNA) expression in gonadal white adipose tissues (WATs) by deep sequencing, bisulfite pyrosequencing, and real-time quantitative polymerase chain reaction. Pregnant CD-1 mice (F0) were dosed daily with 0, 5, or 500 μg/kg/d BPA during gestational days 9 to 18, and the weaned F1 animals were fed ad libitum with standard chow until they were euthanized at 19 weeks old. In the vehicle-exposed F1 animals, fggy promoter showed a clear bimodal pattern of very strong (55% to 95%) or very weak (5% to 30%) DNA methylation occurring at nearly equal incidence with no intermediate strength. Promoter hypermethylation completely suppressed mRNA expression. BPA exposure eliminated this naturally occurring dichotomy, shifting fggy promoter toward the hypomethylation state to release transcriptional suppression. The strength of Fggy mRNA expression significantly correlated with increased whole body weight and gonadal fat weight of males but not females. Bioinformatics studies showed that expression of Fggy mRNA is stronger in mouse WATs than in brown adipose tissues and enhanced in gonadal fat by diet-induced obesity. These observations suggest that prenatal exposure to BPA may disrupt the physiological bimodal nature of epigenetic regulation of fggy in mouse WATs, possibly contributing to the adult-onset obesity phenotype., (Copyright © 2018 Endocrine Society.)

Benign prostatic hyperplasia (BPH) and bladder outlet obstruction (BOO) are common in older men and can contribute to lower urinary tract symptoms that significantly impact quality of life. Few existing models of BOO and BPH use physiological levels of hormones associated with disease progression in humans in a genetically manipulable organism. We present a model of BPH and BOO induced in mice with testosterone (T) and 17β-estradiol (E(2)). Male mice were surgically implanted with slow-releasing sc pellets containing 25 mg T and 2.5 mg E(2) (T+E(2)). After 2 and 4 months of hormone treatment, we evaluated voiding patterns and examined the gross morphology and histology of the bladder, urethra, and prostate. Mice treated with T+E(2) developed significantly larger bladders than untreated mice, consistent with BOO. Some mice treated with T+E(2) had complications in the form of bladder hypertrophy, diverticula, calculi, and eventual decompensation with hydronephrosis. Hormone treatment caused a significant decrease in the size of the urethral lumen, increased prostate mass, and increased number of prostatic ducts associated with the prostatic urethra, compared with untreated mice. Voiding dysfunction was observed in mice treated with T+E(2), who exhibited droplet voiding pattern with significantly decreased void mass, shorter void duration, and fewer sustained voids. The constellation of lower urinary tract abnormalities, including BOO, enlarged prostates, and voiding dysfunction seen in male mice treated with T+E(2) is consistent with BPH in men. This model is suitable for better understanding molecular mechanisms and for developing novel strategies to address BPH and BOO.

Over 6 billion pounds per year of the estrogenic monomer bisphenol A (BPA) are used to manufacture polycarbonate plastic products, in resins lining metal cans, in dental sealants, and in blends with other types of plastic products. The ester bond linking BPA molecules in polycarbonate and resins undergoes hydrolysis, resulting in the release of free BPA into food, beverages, and the environment, and numerous monitoring studies now show almost ubiquitous human exposure to biologically active levels of this chemical. BPA exerts estrogenic effects through the classical nuclear estrogen receptors, and BPA acts as a selective estrogen receptor modulator. However, BPA also initiates rapid responses via estrogen receptors presumably associated with the plasma membrane. Similar to estradiol, BPA causes changes in some cell functions at concentrations between 1 pM and 1 nM, and the mean and median range of unconjugated BPA measured by multiple techniques in human pregnant maternal, fetal, and adult blood and other tissues exceeds these levels. In contrast to these published findings, BPA manufacturers persist in describing BPA as a weak estrogen and insist there is little concern with human exposure levels. Our concern with human exposure to BPA derives from 1) identification of molecular mechanisms mediating effects in human and animal tissues at very low doses, 2) in vivo effects in experimental animals caused by low doses within the range of human exposure, and 3) widespread human exposure to levels of BPA that cause adverse effects in animals.

The regulation of the preovulatory release of LH by steroids was examined in the mouse, a species in which ovulation is strongly influenced by priming pheromones. Ovariectomized mice were implanted with estradiol in Silastic capsules to involve negative feedback. Preovulatory-like LH surges then were induced by injections of either estradiol benzoate (EB) or progesterone. LH surges were not observed in the absence of steroid injection. LH surges always occurred at lights out on a 14-h light, 10-h dark cycle on the day after EB injection but occurred on the same day as progesterone injection. The amount of EB or progesterone injected seemed unimportant but, in either case, had to be given within a limited diurnal period of sensitivity. LH surges comparable to those of intact proestrous females were produced either by injecting both EB and progesterone or by manipulating the background dose of encapsulated estradiol. In the latter regard, when ovariectomized females were implanted with a wide range of doses of estradiol (0.1--1000 microgram/capsule), a decided window phenomenon became apparent. That is, LH surging could be induced by steroid injections only within a limited range of background doses of encapsulated estradiol. The relationship of the above findings to the pheromonal control of LH secretion and ovulation in mice is as yet unclear.