Breast cancer epidemiology : summary and future directions

Epidemiologic reviews, 1993

Abstract

The most common cancer in US women and the 2nd leading cause of cancer death is breast cancer.

Between 1980-1987 in the US. age-adjusted incidence rates of breast cancer rose rapidly. They are also rising rapidly in several Asian countries (e.g., in Japan) which have the lowest incidence rates. These rapid increases may mean that environmental factors are responsible.

Incidence rates rise greatly with age until the late 40s. US women at highest risk of breast cancer are Jewish women, urban women, single women, and women living in the northern US. Women at lowest risk include Mormon and Seventh-Day Adventist women, Hispanic and Asian women, rural women, women living in the southern US, and married women.

Factors that have a relative risk greater than 2 are

  • mother and sister with history of breast cancer, especially if diagnoses at an early age;
  • atypical epithelial cells in nipple aspirate fluid;
  • nodular densities on the mammogram;
  • history of cancer in 1 breast;
  • mother or sister with history of breast cancer;
  • biopsy-confirmed benign proliferative breast disease;
  • hyperplastic epithelial cells without atypia in nipple aspirate fluid;
  • and radiation to chest in moderate to high doses.

Ovarian hormones appear to stimulate cell division in the breast, thus elevated levels may be risk factors.

Exogenous hormones may also increase the risk. Women are exposed to these exogenous hormones through

  • estrogen replacement therapy,
  • progestin only pills,
  • oral contraceptives,
  • long-acting injectable contraceptives,
  • and diethylstilbestrol.

Postmenopausal obesity increases the risk while premenopausal obesity decreases the risk. A high fat diet in childhood and adolescence may increase the risk. Alcohol drinking may also increase the risk.

Older, white, and nulliparous women are more likely to have estrogen receptor-positive cancers.

Breast cancer in males tends to share the same risk factors as well as its own unique factors.

Prevention of postmenopausal obesity is the only established primary prevention effort. Screening is the only secondary prevention means.

Sources

DES DIETHYLSTILBESTROL RESOURCES

Increased Breast Cancer risk in DES-Exposed Progeny

Maternal exposure to diethylstilbestrol during pregnancy and increased breast cancer risk in daughters, 2014

Study Summary

The idea that susceptibility to breast cancer is determined not only through inherited germline mutations but also by epigenetic changes induced by alterations in hormonal environment during fetal development is gaining increasing support. Using findings obtained in human and animal studies, this review addresses the mechanisms that may explain why daughters of mothers who took synthetic estrogen diethylstilbestrol (DES) during pregnancy have two times higher breast cancer risk than women who were not exposed to it. The mechanisms likely involve epigenetic alterations, such as increased DNA methylation and modifications in histones and microRNA expression.Further, these alterations may target genes that regulate stem cells and prevent differentiation of their daughter cells. Recent findings in a preclinical model suggest that not only are women exposed to DES in utero at an increased risk of developing breast cancer, but this risk may extend to their daughters and granddaughters as well. It is critical, therefore, to determine if the increased risk is driven by epigenetic alterations in genes that increase susceptibility to breast cancer and if these alterations are reversible.

Abstracts

In this review, findings related to in utero DES exposure and breast cancer are discussed for the purpose of weighing evidence as to whether fetal hormonal environment can impact breast cancer risk in women several decades later. Since causal studies can readily be performed using animal models, findings obtained in DES-exposed mouse and rat offspring also are discussed. Importantly, animal studies were done prior to any epidemiological studies addressing a possible link between maternal DES exposure and breast cancer risk among daughters could be performed. By the 1980s, exposed daughters in the cohorts began to be old enough to develop breast cancer and several human studies have been performed since to determine if maternal exposure to DES during pregnancy increases an offspring’s breast cancer risk.

…”The animal studies show that the doses of DES relevant to pregnant women increased later risk of developing mammary tumors. Specifically, female offspring of rat dams exposed to a total of 1.2 μg DES either on gestation week 2 or 3, to 0.6 μg or 4 μg DES on both gestation days 15 and 18 (all via injection), or via diet to 0.1, 1 or 10 ppm DES between gestation days 13 and 21 (week 3) exhibited increased mammary cancer risk. An increase in risk also was seen in rats exposed to a single dose of 0.1, 1 or 10 μg or less of DES at birth.” …

…”Importantly, in utero exposure to DES leads to an increase in terminal end buds (TEBs) numbers. It is thus possible that one of the mechanisms causing an increase in mammary cancer risk in DES offspring is an increase in the number of targets for malignant transformation.”…

…”Several published studies have investigated breast cancer risk in the daughters of DES mothers, the majority of which were cohort studies done in the US. As the women in the cohorts aged, their breast cancer risk grew higher, compared with matched non-exposed controls. The findings clearly indicate that after age 40 years the incidence of breast cancer is at least two-fold higher in the daughters of DES-exposed mothers. Many pregnant women in Europe and Australia also used DES, but the peak exposure occurred 10 to 20 years later than in the US, and this probably explains why a recent study done in Europe found a trend but not a significant increase in breast cancer risk among them. Once the European daughters reach the age when breast cancer is more commonly detected, they too are likely to exhibit a significant increase in breast cancer risk.”…

To summarize, animal and human studies have generated similar findings and indicate that there is a causal link between maternal exposure to DES during pregnancy and increased breast cancer risk among female offspring. According to animal studies, the increase in risk may reflect the presence of a higher number of TEBs in the mammary epithelium in the DES offspring. Baik and colleagues have proposed that the increase in mammary epithelial cells in in utero estrogen-exposed females is caused by a high number of mammary stem cells or an increase in their potential to generate daughter cells. Our unpublished data support this conclusion”

Epigenetic alterations induced by in utero diethylstilbestrol exposure

We and others have observed that the expression of DNA methyltransferases (DNMTs) is persistently altered in estrogen-regulated tissues following estrogenic exposures during early life. In utero exposure to DES is reported to increase the expression of DNMT1 in the epididymis and uterus. We found that DNMT1 expression is increased in the mammary glands of adult rat offspring of dams exposed to ethinyl estradiol during pregnancy. These changes provide a key regulatory layer to influence gene expression in the mammary gland and perhaps breast tumors of individuals exposed to DES or other estrogenic compounds in utero.

The effects of maternal diethylstilbestrol exposure are not limited to the F1 generation?

Some researchers have begun to investigate whether the effects of maternal DES exposure during pregnancy extend to the third generation in humans. Although there is no evidence that DES granddaughters have cervical and ovarian abnormalities similar to DES daughters, there is evidence that they may have more menstrual irregularities and a higher rate of infertility than non-exposed granddaughters. In addition, DES granddaughters may have a slightly higher risk of ovarian cancer. The granddaughters are still too young to assess whether they might also be at an increased risk of developing breast cancer.

Millions of women in the US, Europe and Australia have been exposed to DES in the womb, and consequently exhibit about a two times higher breast cancer risk than unexposed women. The increase in risk may not be limited to the DES-exposed daughters, but could also increase breast cancer risk in granddaughters and great granddaughters. Such outcome would be consistent with the findings we obtained in studies using a synthetic estrogen ethinyl estradiol (EE2). If DES has similar effects to ethinyl estradiol on the transgenerational increase in breast cancer risk, it is urgent to find ways to stop the cycle of inheritance, and also prevent breast cancer in DES-exposed granddaughters and great granddaughters.

To achieve this goal, we need to understand how maternal DES exposure during pregnancy increases a daughter’s breast cancer risk. A plausible model is proposed in the featured image. It is evident from studies done in animal models that in utero DES exposure induces epigenetic changes in reproductive tract tissues and the breast. DES exposure might also have induced epigenetic changes in primordial germ cells and consequently germ cells, and further be detectable in the somatic cells in granddaughters and great granddaughters. We are not aware of any study that has compared epigenetic changes in germ cells and the next generation somatic cells in individuals exposed to DES or other endocrine disruptors in utero. Second, we should investigate whether the transgenerational increase in breast cancer risk can be prevented with drugs that reverse epigenetic modifications. Our preliminary studies in mice suggest that this is achievable in daughters by using the well-tolerated and non-toxic histone deacetylase inhibitor valproic acid and DNMT inhibitor hydralazine. However, whether these compounds also prevent an increase in granddaughters and great granddaughters in experimental models remains to be investigated.

Sources

  • Full study (free access) : Maternal exposure to diethylstilbestrol during pregnancy and increased breast cancer risk in daughters, Breast cancer research : BCR, NCBI PubMed PMC4053091, 2014.
  • Featured image : Proposed model to explain an increase in breast cancer risk in daughters, and possibly granddaughters and great granddaughters, of mothers who took diethylstilbestrol during pregnancy. DES, diethylstilbestrol; TDLU, terminal ductal lobular unit; TEB, terminal end bud. PMC4053091/figure/F1.
DES DIETHYLSTILBESTROL RESOURCES

DES Implications for the Third Generation

image of Grandson

The Health Effects of Diethylstilbestrol Revisited

Abstract

“… DES has been associated with increased risk of reproductive tract tumors in third-generation mice, that is, mice whose grandmothers were exposed to DES. These tumors have included uterine adenocarcinomas and sarcomas and benign ovarian tumors in females as well as tumors in the rete testis in males.

By identifying persons with known exposure, as well as their children, potential participants for studies of the long-term effects of DES could also be identified. With appropriate samples and further research, greater knowledge of the health effects of DES on the children and grandchildren of women who took DES could be gained. Persons who may have been exposed to DES may find national websites and organizations (helpful to access current research and health information as it becomes available.”

Sources

  • The health effects of diethylstilbestrol revisited, Journal of obstetric, gynecologic, and neonatal nursing : JOGNN, NCBI PubMed, PMID: 16020417, 2005 Jul-Aug.
DES DIETHYLSTILBESTROL RESOURCES

Increased Risk of Cancer in DES Grandsons and Granddaughters

Offspring of women exposed in utero to diethylstilbestrol (DES): a preliminary report of benign and malignant pathology in the third generation, 2008

Abstract

BACKGROUND
Animal studies suggest that prenatal exposure to the synthetic estrogen diethylstilbestrol (DES) causes epigenetic changes that may be transmitted to the next generation. Specifically, these studies show an elevated incidence of reproductive tumors in the female offspring of prenatally-exposed mice.

METHODS
We assessed cancer and benign pathology diagnoses occurring in the offspring of women whose prenatal exposure to DES (or lack of exposure) was verified by medical record. Our data arose from 2 sources: the mothers’ reports of cancers occurring in 8216 sons and daughters, and pathology-confirmed cancers and benign diagnoses self-reported by a subset of 793 daughters.

RESULTS
Although statistical power is limited, our data are consistent with no overall increase of cancer in the sons or daughters of women exposed in utero to DES. Based on pathology-confirmed diagnoses reported by the daughters, we saw no association between DES and risk of benign breast disease or reproductive tract conditions. Based on 3 cases, the incidence of ovarian cancer was higher than expected in the daughters of women exposed prenatally to DES.

CONCLUSIONS
Our data do not support an overall increase of cancer risk in the sons or daughters of women exposed prenatally to DES, but the number of ovarian cancer cases was greater than expected. While preliminary, this finding supports continued monitoring of these daughters.

Third-Generation Cohort

In 2001, the NCI assembled the third-generation cohort, consisting of the adult daughters (≥18 years of age) of DES-exposed and unexposed second-generation women.37 A review of parity records at all 5 study centers identified 763 exposed and 577 unexposed mothers of 966 exposed and 815 unexposed age-eligible daughters. About half of the mothers, 414 (54%) of the exposed and 297 (52%) of the unexposed, gave permission to contact 515 (53%) exposed and 383 (47%) unexposed daughters. The questionnaires, which queried daughters for hormonal and reproductive information, screening histories, and medical events (including gynecologic biopsies, breast biopsies, and cancer diagnoses), were returned by 793 (88%) of 898 daughters, including 463 (90%) exposed and 330 (86%) unexposed. Pathology reports were obtained to verify self-reported diagnoses and biopsies. A study-related review of histology slides confirmed 1 of 2 reported cases of borderline ovarian cancer. Slides were unavailable for the second case, which involved metastatic disease.

The confirmation of cancers occurring in the subset of adult daughters participating in the third-generation study was excellent. Of the 8 self-reported cancers, 7 (5 exposed, 2 unexposed) were confirmed by pathology; consent was not obtained to confirm a melanoma reported by an unexposed woman. For other conditions, confirmation of benign biopsies was reasonably good, generally exceeding 60%.

DES Follow-up Study Summary

Studies have shown a slightly increased risk of breast cancer in women who were given Diethylstilbestrol (DES) while they were pregnant. Their daughters, who were exposed to DES prenatally (before they were born), have an elevated risk of reproductive tract conditions, including a rare vaginal cancer. A question now being studied is whether DES health effects can be passed from the prenatally exposed women to their offspring (intergenerational transmission).

Studies in mice suggest that intergenerational transmission of DES health effects may be possible. Recent evidence indicates that prenatal exposure to DES may cause changes in the behavior of genes that influence hormones and the development of the female reproductive tract. These changes in gene behavior may be passed on to the next generation. Evidence for intergenerational transmission comes from mouse studies showing a higher number of reproductive tract tumors in the daughters of prenatally exposed female mice. We used the DES Follow-up Study data to assess whether cancer was more common in the offspring of women who were prenatally exposed to DES. Cancers affecting these offspring (the third generation) were identified using two approaches. First, we asked women participating in the DES Follow-up Study to report cancers diagnosed in their 8,216 third generation sons and daughters. Second, we asked 793 third generation daughters participating in the Third Generation Study to tell us about their cancers. We also asked the third generation daughters to tell us about their reproductive tract and breast biopsies. Next we confirmed the reported biopsies and cancers by checking the medical records of these third generation daughters.

Our results did not show an overall increase of cancer in the sons or in the daughters of prenatally DES-exposed women. However, based on only three cases, the number of ovarian cancers was higher than expected in the daughters of women exposed prenatally to DES. Because of the small number of cases, this result must be considered preliminary. The association may be a chance finding or may be due to the way in which the data were reported or collected. We did not find an association between DES and benign breast disease or reproductive tract conditions, but most of the women are too young for a meaningful assessment of these outcomes. Further follow-up is needed to assess whether prenatal DES exposure can affect the third generation in humans.

Sources

  • Full study (free access) : Offspring of Women Exposed In Utero to Diethylstilbestrol (DES): A Preliminary Report of Benign and Malignant Pathology in the Third Generation, Epidemiology doi: 10.1097/EDE.0b013e318163152a, March 2008.
  • Featured image credit oaks.journals.
  • NCIDES Follow-up Study Published Papers.
DES DIETHYLSTILBESTROL RESOURCES

Birth Defects in the Sons and Daughters of Women who were Exposed in utero to Diethylstilbestrol (DES)

Possible association between the DES mothers exposure and birth defects in DES grandsons, DES granddaughters

2010 Study Abstract

Background
Prenatal exposure to diethylstilbestrol (DES) is associated with adverse health outcomes, including anatomic anomalies of the reproductive tract in women and of the genitourinary tract in men. The mouse model, which replicates many DES-related effects seen in humans, suggests that prenatal DES exposure causes alterations that may affect the next generation of offspring.

Methods
Women participating in a large multi-center study of prenatal DES exposure were asked to report birth defects occurring among 4,029 sons and 3,808 daughters (i.e., the third generation). A subcohort of 793 third generation daughters were also queried for birth defects. We used logistic regression models to generate odds ratios and 95% confidence intervals for the association between prenatal DES exposure in the mother and birth defects in the offspring.

Results
Based on the mothers’ reports, overall birth defects were elevated in the sons (OR = 1.53; 95% CI = 1.04, 2.23) and in the daughters (OR = 2.35; 95% CI = 1.44, 3.82). Most estimates of association were imprecise, but daughters appeared to have an excess of heart conditions (OR = 4.56; 95% CI = 1.27, 16.34.

Conclusions
Our data suggest a possible association between the mother’s prenatal DES exposure and birth defects in their offspring, particularly in daughters. We cannot, however, rule-out the possible influence of reporting bias. In particular, the exposed daughters’ elevated risk of cardiac defects may be due to the underreporting of these conditions by unexposed mothers.

Sources

  • Birth Defects in the Sons and Daughters of Women who were Exposed in utero to Diethylstilbestrol (DES), International journal of andrology, NCBI PubMed PMC2874639, 2010 April.
  • Featured image credit Nathan Dumlao.
DES DIETHYLSTILBESTROL RESOURCES

Examination of multigenerational transmission of environmental associations

Toward an Emerging Paradigm for Understanding Attention-Deficit/Hyperactivity Disorder and Other Neurodevelopmental, Mental, and Behavioral Disorders

2018 Study Abstract

In Association of Exposure to Diethylstilbestrol During Pregnancy With Multigenerational Neurodevelopmental Deficits, Kioumourtzoglou et al use an approach that is as important as it is underused: an examination of multigenerational transmission of environmental associations. That approach may be the most important from an epidemiological perspective. They report that pollutant exposure to grandparents conveys a 30% increase in risk of ADHD in grandchildren. The findings are novel and contribute to this emerging shift in the understanding of mental and behavioral disorders such as ADHD. The size of the association, similar to many other concurrent risk factors for ADHD, is striking.

Although, as the authors note, the dosages of everyday individual environmental pollutants are generally lower (in developed countries at least) than the dosages of diethylstilbestrol they studied, today’s population is exposed to hundreds of poorly studied, neurodevelopmentally or hormonally active compounds, the interactions among which are unknown. Thus, the actual associations today are difficult to quantify.

The limitations in this study should not be overlooked—genetic associations were not able to be examined (so a genotype-environment correlation might partially account for findings), causality could not be evaluated because of the absence of F1 siblings, and ADHD assessment is limited in population studies. Their finding of a first trimester bias in the association, in particular, should be interpreted very cautiously; the incidence of ADHD in the second, third, and first trimester exposures were all higher than the unexposed group, and the statistical power to detect between-trimester associations was low. As the authors appropriately noted, further work on trimester-specific associations will be of interest. Finally, an epigenetic transmission is not the only possibility (because of third-generation oocyte exposure, as the authors noted), although epigenetic transmission by neuroactive chemicals to the third generation is demonstrated in nonhuman animals.

Sources

  • Toward an Emerging Paradigm for Understanding Attention-Deficit/Hyperactivity Disorder and Other Neurodevelopmental, Mental, and Behavioral Disorders, JAMA Pediatrics doi:10.1001/jamapediatrics.2018.0920, July 2018.
  • Featured image credit Jason Leung.
DES DIETHYLSTILBESTROL RESOURCES

Do endocrine disruptors cause hypospadias?

Based on mouse data, exposure to DES raises the risk of genital malformation in subsequent generations. With a French database of 529 families with DES-exposed mothers, there was significant number of sons born to “DES-daughters” (8/97, P=0.02).

2014 Study Abstract

INTRODUCTION
Endocrine disruptors or environmental agents, disrupt the endocrine system, leading to various adverse effects in humans and animals. Although the phenomenon has been noted historically in the cases of diethylstilbestrol (DES) and dichlorodiphenyltrichloroethane (DDT), the term “endocrine disruptor” is relatively new. Endocrine disruptors can have a variety of hormonal activities such as estrogenicity or anti-androgenicity. The focus of this review concerns on the induction of hypospadias by exogenous estrogenic endocrine disruptors. This has been a particular clinical concern secondary to reported increased incidence of hypospadias. Herein, the recent literature is reviewed as to whether endocrine disruptors cause hypospadias.

METHODS
A literature search was performed for studies involving both humans and animals. Studies within the past 5 years were reviewed and categorized into basic science, clinical science, epidemiologic, or review studies.

RESULTS
Forty-three scientific articles were identified. Relevant sentinel articles were also reviewed. Additional pertinent studies were extracted from the reference of the articles that obtained from initial search results. Each article was reviewed and results presented. Overall, there were no studies which definitely stated that endocrine disruptors caused hypospadias. However, there were multiple studies which implicated endocrine disruptors as one component of a multifactorial model for hypospadias.

CONCLUSIONS
Endocrine disruption may be one of the many critical steps in aberrant development that manifests as hypospadias.

Sources

  • Full text (free access) : Do endocrine disruptors cause hypospadias?, NCBI PubMed PMC4708138, 2014 Dec.
  • Featured image credit Alex Hockett.
DES DIETHYLSTILBESTROL RESOURCES

Transgenerational transmission of DES effects through epigenetic modifications

The history of Distilbène® (Diethylstilbestrol) told to grandchildren – the transgenerational effect

2015 Study Abstracts

Exposure window

The foetal period is particularly conducive to the induction of abnormalities induced by exposure to DES. This may be due to the importance of sex steroids in controlling the development and differentiation of the genital tract. It is also possible that DES is minimally linked with carrier proteins (SHBG poorly secreted by the foetus or alpha-fetoprotein), and that there is an enzymatic immaturity affecting detoxification enzymes, so that defence mechanisms are still partially developed, such as the blood-testis barrier. The importance of the exposure window is also well illustrated by the phenotype difference observed in the mouse exposed during prenatal or neonatal period. Neonatal pre-exposure also leads to the development of uterine cancer in females in adulthood, while these lesions are not found in animals exposed during the prenatal period. In the same way, foetal exposure to weak doses of DES leads to an increase in prostate cancer in male adult animals with an increase in the number of androgen receptors.

Epigenetic modifications

It is likely that by reproducing in rodents the harmful effects ofin utero exposure to DES, allowed the first argumentsin favour of epigenetic modifications originating from the programming of adult diseases. Of course, we cannot exclude the mutagenic effect of high doses of DES that were prescribed to pregnant women. However, such abnormalities that could be induced by oxydated oestrogen derivatives were never really highlighted. Expression of genes involved in the development and structural differentiation of the reproductive tract such as the HOX genes has been shown to be disrupted without DNA structure modifications. In 1997, Li et al. first illustrated epigenetic modifications in an oestrogen-dependent gene, i.e., lactoferrin, determined in the uteri of mice treated with DES neonatally. This gene is overexpressed in adulthood, due to its promoter demethylation, and this overexpression is dose-dependent on neonatal exposure to DES and is associated with susceptibility to uterine cancer in adulthood. This seemingly innocuous experience is an early example of a modification that is not genetic, but epigenetic, induced by foetal or perinatal hormonal environment modulation that will be expressed afterwards in adulthood by induced malignant tumours. By adulthood, it is presumable that these epigeneticmodifications, as demonstrated in hamsters, equally affect the expression of oestrogen-regulated genesin the uterus such as c-jun, c-fos, c-myc, BALC, BCL-2 and BCLX and are involved in uterine cell proliferation and apoptosis as demonstrated in mouse for c-fos.

Transgenerational transmission mechanisms

These epigenetic modifications are also highlighted in a very interesting model developed by Anway et al. This model involved rats that were exposed in utero to the oestrogen-mimicking organochlorine pesticide methoxychlor or to the anti-androgen, antifungal agent, vinclozolin. Their male offspring developed subfertility with decreased production in sperm quality and an increase in post-meiotic germ cell apoptosis associated with epigenetic modifications (hyper- or hypomethylation of CpG islands) of the promoter region from genes expressed by male germ cells. Surprisingly, these changes are found up to the fifth generation, transmitted by the male and not by the female, and therefore transmitted by sperm, which, except for the second-generation male, was not directly exposed to the endocrine disruptor. As we have seen, this DES transgenerational transmission was also found in mice after neonatal exposure in a uterine cancer model during the third generation, or following exposure to a harmful foetal environment with respect to nutrition, stress, hormonal or metabolic disruption, chemical pollutants. Theoretically, in the early stages of gametogenesis, and during the first divisions of the fertilized egg, there is an epigenetic counter reset and the implementation of imprinting phenomena. The molecular mechanisms which may explain the maintenance of multigenerational epigenetic modifications induced by environment are still poorly understood. However, recent works suggest the involvement of small non-coding RNAs, such as the microRNAs proposed in various mouse models, where phenotypic changes could be induced by simply injecting the fertilised egg with microRNA from animal sperm, which has been exposed to the harmful environment and which is responsible for the observed epigenetic modifications.

Sources

  • The history of Distilbène® (Diethylstilbestrol) told to grandchildren – the transgenerational effect, Annales d’endocrinologie, NCBI PubMed PMID: 25934356, 2015 Jul.
  • Featured image credit Kevin Delvecchio.
DES DIETHYLSTILBESTROL RESOURCES

Hypospadias can be transmitted to the DES-exposed third-generation

Prenatal diethylstilbestrol induces malformation of the external genitalia of male and female mice and persistent second-generation developmental abnormalities of the external genitalia in two mouse strains

2014 Study Abstract

Potential trans-generational influence of diethylstilbestrol (DES) exposure emerged with reports of effects in grandchildren of DES-treated pregnant women and of reproductive tract tumors in offspring of mice exposed in utero to DES.

Accordingly, we examined the trans-generational influence of DES on development of external genitalia (ExG) and compared effects of in utero DES exposure in CD-1 and C57BL/6 mice injected with oil or DES every other day from gestational days 12 to 18. Mice were examined at birth, and on 5-120 days postnatal to evaluate ExG malformations. Of 23 adult (>60 days) prenatally DES-exposed males, features indicative of urethral meatal hypospadias (see text for definitions) ranged from 18% to 100% in prenatally DES-exposed CD-1 males and 31% to 100% in prenatally DES-exposed C57BL/6 males. Thus, the strains differed only slightly in the incidence of male urethral hypospadias. Ninety-one percent of DES-exposed CD-1 females and 100% of DES-exposed C57BL/6 females had urethral-vaginal fistula. All DES-exposed CD-1 and C57BL/6 females lacked an os clitoris. None of the prenatally oil-treated CD-1 and C57BL/6 male and female mice had ExG malformations. For the second-generation study, 10 adult CD-1 males and females, from oil- and DES-exposed groups, respectively, were paired with untreated CD-1 mice for 30 days, and their offspring evaluated for ExG malformations. None of the F1 DES-treated females were fertile. Nine of 10 prenatally DES-exposed CD-1 males sired offspring with untreated females, producing 55 male and 42 female pups. Of the F2 DES-lineage adult males, 20% had exposed urethral flaps, a criterion of urethral meatal hypospadias. Five of 42 (11.9%) F2 DES lineage females had urethral-vaginal fistula. In contrast, all F2 oil-lineage males and all oil-lineage females were normal.

Thus, prenatal DES exposure induces malformations of ExG in both sexes and strains of mice, and certain malformations are transmitted to the second-generation.

Sources

  • Full text (free access) : Prenatal diethylstilbestrol induces malformation of the external genitalia of male and female mice and persistent second-generation developmental abnormalities of the external genitalia in two mouse strains, NCBI PubMed PMC4254634, 2014 Oct.
  • Featured image credit figure/F1.
DES DIETHYLSTILBESTROL RESOURCES

Risk factors for hypospadias

The associations found in this study support the hypothesis that genetic predisposition, placental insufficiency, and substances that interfere with natural hormones play a role in the etiology of hypospadias

2007 Study Abstract

Despite being one of the most common congenital defects in boys, the etiology of hypospadias remains largely unknown. In this case-referent study, we evaluated a wide spectrum of potential risk factors for hypospadias. Cases were identified from the hospital information system, and referents were recruited through the parents of the cases. Both parents of cases and referents completed written questionnaires that they received through the mail. Logistic regression analyses were used to assess the independent contribution of different factors to the risk of hypospadias. The final database included 583 cases and 251 referents.

Hypospadias more often occurred in children whose father had hypospadias (OR=9.7; 95%CI: 1.3-74.0) and in children with a low birth weight (OR=2.3; 95%CI: 1.2-4.2). Indications for elevated risks were found when mothers were DES-daughters (OR=3.5; 95%CI: 0.8-15.6), fathers were subfertile (OR=1.8; 95%CI: 0.7-4.5), the parents had undergone fertility treatment (OR=2.3; 95%CI: 0.9-5.8), and in twin or triplet pregnancies (OR=2.0; 95%CI: 0.8-5.1). Maternal use of iron supplements (OR=2.2; 95%CI: 0.8-6.0), maternal smoking (OR=1.5; 95%CI: 1.0-2.4), paternal prescriptive drug use (OR=2.6; 95%CI: 1.1-6.6), and paternal exposure to pesticides (OR=2.1; 95%CI: 0.6-7.1) during the 3 months immediately prior to conception or in the first trimester of pregnancy also appeared to increase the risk of hypospadias.

A strong indication for an increased risk of hypospadias was found among boys whose mothers were exposed to DES in utero – ‘DES-daughters’ – an association reported in a previous article by our group. In 2002, Klip et al. reported the prevalence ratio for hypospadias in sons of DES-daughters to be 21.3 (95%CI: 6.5–70.1), which was the first suggestion of a transgenerational effect of DES in humans. However, the association between intrauterine DES exposure and hypospadias was assessed in a cohort of women with fertility problems, who do not reflect DES-daughters in general. According to our findings, the excess risk of hypospadias appears to be of a much smaller magnitude. This may be explained by the differences in study design, and in the study population in particular, and probably results in a more valid risk estimate that is concordant with findings from a recent study in France. It is possible that DES-related pathology of reproductive structures in DES-daughters interferes with normal fetal development during pregnancy, but other explanations have been suggested as well.

We found no indication that DES-sons ‘transmit’ a predisposition to hypospadias to their sons. Our results also point towards an association between paternal subfertility and hypospadias.

Sources

DES DIETHYLSTILBESTROL RESOURCES