Developmental exposure to estrogens has been shown to affect the musculoskeletal system. Furthermore, recent studies have shown that environmental exposure to estrogen-like compounds is much higher than originally anticipated. The aim of this study was to determine the effects of diethylstilbestrol (DES), a well-known estrogen agonist, on articular cartilage, intervertebral disc (IVD), and bone phenotype.
C57Bl/6 pregnant mice were dosed orally with vehicle (peanut oil) or 0.1, 1.0, and 10 μg/kg/day of DES on gestational days 11 to 14. Male and female pups were allowed to mature without further treatment until 3 months of age, when swim and sedentary groups were formed. After euthanasia, bone mineral density (BMD), bone mineral content (BMC), bone area (BA), and trabecular bone area (TBA) of the lumbar vertebrae and femur were measured by using a PIXImus Bone Densitometer System. Intervertebral disc proteoglycan was measured with the DMMB assay. Histologic analysis of proteoglycan for IVD and articular cartilage was performed with safranin O staining, and degeneration parameters were scored.
Effect of in utero exposure to diethylstilbestrol on lumbar and femoral bone, articular cartilage, and the intervertebral disc in male and female adult mice progeny with and without swimming exercise, Arthritis research and therapy, NCBI PubMed PMID: 22269139, 2012 Jan.
The lumbar BMC was significantly increased in female swimmers at both the highest and lowest dose of DES, whereas the femoral BMC was increased only at the highest. The males, conversely, showed a decreased BMC at the highest dose of DES for both lumbar and femoral bone. The female swim group had an increased BA at the highest dose of DES, whereas the male counterpart showed a decreased BA for femoral bone. The TBA showed a similar pattern. Proteoglycan analysis of lumbar IVDs showed a decrease at the lowest doses but a significant increase at the highest doses for both males and females. Histologic examination showed morphologic changes of the IVD and articular cartilage for all doses of DES.
DES significantly affected the musculoskeletal system of adult mice. Results suggest that environmental estrogen contaminants can have a detrimental effect on the developmental lumbar bone growth and mineralization in mice. Further studies measuring the impact of environmental estrogen mimics, such as bisphenol A, are then warranted.
Exposure to estrogens during various stages of development has been shown to irreversibly influence responsive target organs. The recent finding of the presence of estrogen receptor in both osteoblasts and osteoclasts has suggested a direct role of steroid hormones on bone tissue. Furthermore, estrogens have important effects on bone turnover in both humans and experimental animal models. Thus, this tissue is now regarded as a specific estrogen target tissue.
Alterations in estrogen levels during development affects the skeleton: use of an animal model, Environmental Health Perspectives, NCBI PubMed PMC1518867, 1995 Oct.
To investigate whether a short-term developmental exposure to estrogens can influence bone tissue, we have injected female mice with diethylstilbestrol (DES) from day 1 through day 5 of life. Additionally, a group of pregnant female mice were injected with different doses of DES from day 9 through 16 of pregnancy. Mice were then weaned at 21 days of age, and effects on bone tissue of the female mice were evaluated in adulthood (7-12 months of age).
These short-term treatments did not affect body weight of exposed mice. However, a dose-dependent increase in bone mass, both in the trabecular and compact compartments, was observed in the DES-exposed female offspring. Furthermore, femurs from DES-exposed females were shorter than femurs from controls. A normal skeletal mineralization accompanied these changes in the bone tissue. In fact, a parallel increase in total calcium content of the skeleton was found in concomitance with the increase in bone mass. Estrogen treatment induced an increase in the amount of mineralized skeleton when compared to untreated controls.
In summary, this report shows that alterations of estrogen levels during development can influence the early phases of bone tissue development inducing permanent changes in the skeleton. These changes appear to be related to bone cell programming in early phases of life.
At the present time our result cannot either indicate or rule out any potential teratogenic or carcinogenic effect of the early exposure to DES in the skeleton of these female mice. It is interesting to know, however, that there have been a few self reports of spondylolisthesis in women exposed prenatally to DES (23). Thus, it may be clinically important to further investigate the possibility that exposure of the human population to exogenous estrogens could permanently affect skeletal tissue. In particular, it will be clinically relevent to evaluate whether low or high doses of these steroids could affect the skeleton in different manner, for instance increasing peak bone density or inducing skeletal malformations at higher doses. In conclusion, our results show for the first time that developmental exposure to estrogens during certain stages can permanently influence bone tissue in an animal model. The observed changes appear to be due to an effect on bone cell programming since differences in bone cell number and activity are retained through adulthood.
Estrogens have important effects on bone turnover in both humans and experimental animals models. Moreover, the decreased level of estrogen after menopause appears to be one of the key factors in determining postmenopausal osteoporosis. The presence of estrogen receptor in both osteoblasts and osteoclasts has suggested a direct role of these steroid hormones on bone tissue. Thus, this tissue is now regarded as a specific estrogen target tissue. Exposure to estrogens during various stages of development has been shown to irreversibly influence responsive target organs. We have recently shown that transient developmental neonatal exposure (days 1-5 of life) of female mice to estrogen resulted in an augmented bone density in the adult animals.
The aim of the present study was to evaluate whether short-term modification of maternal estrogen levels during pregnancy would induce changes in the skeleton of the developing fetuses and to identify any long-term alterations that may occur.
Alterations of maternal estrogen levels during gestation affect the skeleton of female offspring, Endocrinology, NCBI PubMed PMID: 8612556, 1996 May.
Pregnant mice were injected with varying doses (0.1-100 micrograms/kg maternal BW) of the synthetic estrogen diethylstilbestrol (DES) from day 9-16 of pregnancy. Offspring were weaned at 21 days of age, and effects on bone tissue of the female mice were evaluated in adulthood (6-9 months of age).
Prenatal DES treatment(s) did not significantly affect BW. However, a dose-dependent increase in bone mass, both in the trabecular and cortical compartments, was observed in the prenatal DES-exposed female offspring. Furthermore, long bones of DES-exposed females were shorter than controls. Normal skeletal mineralization accompanied these changes in the bone tissue, as shown by a parallel increase in skeletal calcium content. Double tetracycline labeling performed in 6-month-old DES-exposed animals showed an increase in mineral apposition rate in adult DES-exposed mice as compared with untreated control animals, although no significant difference in the circulating estrogen levels was found in animals of this age. Experiments were then performed to evaluate whether perturbation of the estrogen surge at puberty in these diethylstilbestrol (DES)-exposed mice could reverse the observed changes. Femur length was chosen as a marker of potential estrogenic effect. Prepubertal ovariectomy of the prenatally DES-treated animals could only partially reverse the effects observed in the skeleton of the DES-treated animals. Further experiments were performed to evaluate whether these changes could have occurred in utero. CD-1 pregnant female mice were injected with DES (100 micrograms/kg maternal BW) from days 9-15 of gestation. On day 16 of gestation, fetuses were examined and stained by a standard Alizarin Red S and Alcian Blue procedure to visualize calcified and uncalcified skeletal tissue. Estrogen treatment induced an increase in the amount of calcified skeleton as compared with untreated controls and also a decrease in the length of long bones, strongly suggesting a change in both endochondral ossification and endosteal and periosteal bone formation.
In summary, these data show, for the first time, that alterations in the maternal estrogenic levels during pregnancy can influence early phases of fetal bone tissue development and subsequently result in permanent changes in the skeleton. Finally, the effect of this short-term estrogen treatment can be seen in the fetal skeleton, suggesting an estrogen-imprinting effect on bone cell-programming in fetal life because treatment effects on bone cell turnover can be observed later in adult life.
In 1970, and article documented the correlation between in utero DES exposure and development of a rare vaginal cancer, clear-cell adenocarcinoma. In 1971, the US Federal Drug Administration contraindicated the drug from use during pregnancy.
DES exposure: implications for childbearing, The International journal of childbirth education : the official publication of the International Childbirth Education Association, NCBI PubMed PMID 12286762, 1992 Nov-Dec.
Since then, controlled studies have proven that administration of DES was associated with increased spontaneous abortions, premature delivery, complications during delivery, and neonatal deaths.
DES-exposed daughters in reproductive age faced increased rates of infertility, spontaneous abortion, ectopic pregnancy, and premature delivery. DES-exposed daughters may suffer more pelvic inflammatory disease and dysmenorrhea. A 1988 study related the infertility experience of 796 daughters born to mothers who took part in a double-blind, controlled study of DES use during pregnancy at a Chicago hospital in 1951 and 1952. In early 1986, primary infertility was reported by 33% of the DES-exposed daughters as opposed to 14% of the unexposed subjects. However, 81% of pregnant DES daughters have at least one full-term live birth. Uterine abnormalities including a T-shaped or hypoplastic cavity, a septate uterus, intrauterine adhesions, or irregular uterine margins were documented in 46% of the DES-exposed daughters with primary infertility. Vaginal adenosis is reported to occur in 30%-90% of DES-exposed daughters. Cervical hypoplasia and shortened cervical structure are the primary cervical abnormalities.
In addition, for 10 years researchers have observed certain alterations in the immune systems of DES-exposed women.
Most physicians recommend alternative birth control methods to oral contraceptives to avoid an additional exposure to synthetic estrogens.
Executive Summary to EDC-2: The Endocrine Society’s Second Scientific Statement on Endocrine-Disrupting Chemicals, The Endocrine Society, dx.doi.org/10.1210/er.2015-1093, September 28, 2015. Full study: EDC-2: The Endocrine Society’s Second Scientific Statement on Endocrine-Disrupting Chemicals, The Endocrine Society, dx.doi.org/10.1210/er.2015-1010, November 06, 2015.
Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans—especially during development—may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, and epigenetic changes, thereby producing effects in exposed individuals as well as their descendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans.
In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest:
obesity and diabetes;
hormone-sensitive cancers in females;
and neurodevelopment and neuroendocrine systems.
Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in a range that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings can be much better translated to human health.
Armed with this information, researchers, physicians, and other healthcare providers can guide regulators and policymakers as they make responsible decisions.
Discussion (DES and Fertility-specific)
Diethylstilbestrol and beyond: perhaps the best-studied endocrine-based example is in utero exposure to diethylstilbestrol (DES), a potent synthetic nonsteroidal estrogen taken by pregnant women from the 1940s to 1975 to prevent miscarriage and other complications. DES was prescribed at doses from less than 100 mg (in most cases) upward to 47 000 mg, with a median dose of 3650 to 4000 mg in the United States (IARC 2012). Most women received low doses (ie, 5 mg) and increased their intake (up to 125 mg) as symptoms or pregnancy progressed, translating to doses of about 100 μg/kg to 2 mg/kg DES per day. In 1953, a study proved DES was ineffective. Its use was discontinued when a subset of exposed daughters presented with early-onset vaginal clear-cell adenocarcinoma, with a 40-fold increase in risk compared to unexposed individuals. A highly significant incidence ratio for clear-cell adenocarcinoma was also found in the Dutch DES cohort, a population that may have had lower exposures than US women. It was subsequently determined that exposed offspring of both sexes had increased risk for multiple reproductive disorders, certain cancers, cryptorchidism (boys), and other diseases, although the risk for sons is more controversial. New data are emerging to implicate increased disease risk in grandchildren. Not surprisingly, a plethora of examples is emerging for increased disease susceptibility later in life as a function of developmental exposures to EDCs that include BPA, phthalates, PCBs, pesticides, dioxins, and tributyltin (TBT), among others.
Epigenetics and transgenerational effects of EDCs: EDC-induced epigenetic changes are also influenced by dose of exposure, and they are tissue specific. Thus, it is important to consider both dose of EDC and the tissue before making firm conclusions about the epigenetic effects of EDCs. DNA methylation changes are the best-studied mechanism in this regard. For example, prenatal exposure to DES caused hypermethylation of the Hoxa10 gene in the uterus of mice and was linked to uterine hyperplasia and neoplasia later in life. Beyond the effects of prenatal exposure to DES on the daughters exposed in utero are suggestions that this leads to transgenerational effects of the chemical on the reproductive system, although whether this is linked to DNA methylation changes in humans is unknown.
Little is known about the ability of EDCs to cause histone modifications and whether this leads to transgenerational effects in animals or humans. The herbicides paraquat and dieldrin caused histone modifications in immortalized rat mesencephalic dopaminergic cells, and the insecticide propoxur causes histone modifications in gastric cells in vitro. DES caused histone deacetylation in the promoter region of the cytochrome P450 side chain cleavage (P450scc) gene. Further studies, however, need to be conducted to identify other EDCs causing histone modifications in animals and humans and to determine whether such modifications lead to transgenerational effects.
Female Reproductive Health: in the past 5 years, no new information became available on the effects of DES on the postnatal human ovary. Recent animal studies indicate that DES adversely affected the postnatal ovary. Neonatal exposure to DES inhibited germ cell nest breakdown (408) and caused the formation of polyovular follicles in mice, likely by interfering with the ERβ pathway and inhibiting programmed oocyte death and germ cell loss. It also reduced the primordial follicle pool and increased atresia in prepubertal lambs, and it caused polyovular ovaries in hamsters. Although these previous studies provide solid evidence that DES adversely affects ovarian structure in a variety of species, studies are needed to determine whether other synthetic estrogens adversely affect the ovary.
Effects of EDCs on uterine structure and function: synthetic estrogens are well known disruptors of uterine structure and function in humans and animals. Consistent with previous studies, recent data indicate that neonatal DES exposure caused endometrial hyperplasia/dysplasia in hamsters and increased uterine adenocarcinoma and uterine abnormalities in Donryu rats. Neonatal DES exposure also caused the differential expression of 900 genes in one or both layers of the uterus. Specifically, DES altered multiple factors in the PPARγ pathway that regulate adipogenesis and lipid metabolism, and it perturbed glucose homeostasis, suggesting that DES affects energy metabolism in the uterus. In the mouse uterus, DES altered the expression of chromatin-modifying proteins and Wnt signaling pathway members, caused epigenetic changes in the sine oculis homeobox 1 gene, and decreased the expression of angiogenic factors. DES also altered the expression of genes commonly involved in metabolism or endometrial cancer in mice, and it activated nongenomic signaling in uterine myometrial cells and increased the incidence of cystic glands in rats.
Effects of EDCs on the vagina: only a limited number of studies assessed the effects of EDCs on the vagina, and of these, all but one on phthalates focused on DES. A recent study of women showed an association between in utero exposure to DES and clear cell carcinoma of the vagina, confirming previous findings. Furthermore, DES disrupted the expression of transformation-related protein 63, which makes cell fate decisions of Müllerian duct epithelium and induces adenosis lesions in the cervix and vagina in women.
Studies in mice showed that DES induced vaginal adenosis by down-regulating RUNX1, which inhibits the BMP4/activin A-regulated vaginal cell fate decision; induced epithelial cell proliferation and inhibited stromal cell proliferation (520); and caused persistent down-regulation of basic-helix-loop-helix transcription factor expression (Hes1, Hey1, Heyl) in the vagina, leading to estrogen-independent epithelial cell proliferation. Neonatal exposure to DES caused persistent changes in expression of IGF-1 and its downstream signaling factors in mouse vaginas. It also up-regulated Wnt4, a factor correlated with the stratification of epithelial cells, in mouse vaginas. Interestingly, the simultaneous administration of vitamin D attenuated the ability of DES to cause hyperplasia of the vagina in neonatal mice.
In the one study in the previous 5 years that did not focus on DES, polypropylene and polyethylene terephthalate did not increase vaginal weight in Sprague-Dawley rats. Although a few studies have been conducted during the previous 5 years on the effects of EDCs on the vagina, such studies are very few in number, small in scope, and focused on DES. Thus, future studies are needed in this largely understudied area before we fully appreciate whether other EDCs impair the vagina.
Premature ovarian failure/early menopause: combined data from three studies on DES indicated that in utero exposure was associated with an increased lifetime risk of early menopause in women (602). However, animal studies have not determined whether DES exposure causes premature ovarian failure. Thus, future studies should focus on this issue.
Fibroids: a few recent studies confirmed the known association between DES exposure and fibroids. In the Sister Study, in utero exposure to DES was positively associated with early-onset fibroids. Similarly, in the Nurses’ Health Study II, prenatal DES exposure was associated with uterine fibroids, with the strongest risk being for women exposed to DES in the first trimester. Given the consistency in findings, future studies should be focused on determining the mechanism by which DES exposure increases the risk of fibroids.
Fertility of tall girls treated with high-dose estrogen, a dose-response relationship, National Institutes of Health, NCBI PubMed PMID 22723330, 2012 Sep. Full text: The Endocrine Society, dx.doi.org/10.1210/jc.2012-1078, June 20, 2012.
High-dose estrogen treatment to reduce final height of tall girls increases their risk for infertility in later life.
The aim was to study the effect of estrogen dose on fertility outcome of these women.
We conducted a retrospective cohort study of university hospital patients.
We studied 125 tall women aged 20-42 yr, of whom 52 women had been treated with 100 μg and 43 with 200 μg of ethinyl estradiol (EE) in adolescence.
Time to first pregnancy, treatment for infertility, and live birth rate were measured.
The time to first pregnancy was increased in treated women. Of untreated women, 80% conceived within 1 yr vs. 69% of women treated with 100 μg EE and 59% of women treated with 200 μg EE. This trend of increased time to pregnancy with increasing estrogen dose was significant (log rank trend test, P = 0.01). Compared with untreated women, fecundability was reduced in women treated with both 100 μg EE [hazard ratio = 0.42; 95% confidence interval (CI), 0.19-0.95] and 200 μg EE (hazard ratio = 0.30; 95% CI, 0.13-0.72). We also observed a significant trend in the incidence of treatment for infertility with increased estrogen dose (P = 0.04). Fecundity was affected in women treated with 200 μg EE who had reduced odds of achieving at least one live birth (odds ratio = 0.13; 95% CI, 0.02-0.81), but not in women treated with 100 μg EE.
We report a dose-response relationship between fertility in later life and estrogen dose used for the treatment of tall stature in adolescent girls; a higher estrogen dose is associated with increased infertility.
It has been shown that high-dose estrogen treatment to reduce final height of tall girls increases their risk for infertility in later life (3, 4). Here, we studied the effect of estrogen dose on fertility outcome of these women. We compared women who received no treatment to women who received either 100 μg EE or 200 μg EE. Our study confirms that tall women treated with high-dose estrogen have an increased time to pregnancy and experience more fertility problems compared with untreated women. We demonstrate for the first time that the association between estrogen treatment and the observed infertility is dose-dependent.
Although human studies on the effects of treatment with estrogens have mostly focused on OCP users, animal studies have focused on environmental exposure to EE as an endocrine-disruptor and on the effects of diethylstilbestrol (DES). In rodents, both in utero and postnatal exposure to EE or DES produces permanent adverse effects on the developing female reproductive system. Animal studies on in utero exposure to DES have shown disruption at the follicle level. In DES-exposed mice, reduced numbers of primordial follicles and of oocytes after ovulation induction have been found. Neonatal exposure to DES in lambs reduces the primordial follicle pool by stimulating their initial recruitment, resulting in increased numbers of atretic follicles. Finally, DES induces transient changes in gene expression during gestation; these changes could be involved in follicle development, rate of atresia, or patterns of secretion or metabolism of steroid hormones. These animal studies suggest that pharmacological doses of estrogens may influence fertility in many ways and at various time points. This knowledge, although difficult to extrapolate, may help in better understanding the mechanism behind the observed infertility in tall women treated with high-dose estrogen.
Previously, it has been shown that a considerable number of tall women treated with high-dose estrogen in adolescence suffer from primary ovarian insufficiency with concomitant early follicle pool depletion diagnosed by increased serum FSH levels, decreased serum anti-Müllerian hormone levels, and low antral follicle counts. Although the mechanism behind this accelerated follicle loss observed in these women remains unknown, based on our results we conclude that estrogen may play a key dose-dependent role. This is supported by a study on in utero exposure of women to DES, who reported an earlier age at menopause with cumulating doses of DES.
There is growing interest in the possible health threat posed by endocrine-disrupting chemicals (EDCs), which are substances in our environment, food, and consumer products that interfere with hormone biosynthesis, metabolism, or action resulting in a deviation from normal homeostatic control or reproduction.
In this first Scientific Statement of The Endocrine Society, we present the evidence that endocrine disruptors have effects on male and female reproduction, breast development and cancer, prostate cancer, neuroendocrinology, thyroid, metabolism and obesity, and cardiovascular endocrinology.
Results from animal models, human clinical observations, and epidemiological studies converge to implicate EDCs as a significant concern to public health. The mechanisms of EDCs involve divergent pathways including (but not limited to) estrogenic, antiandrogenic, thyroid, peroxisome proliferator-activated receptor γ, retinoid, and actions through other nuclear receptors; steroidogenic enzymes; neurotransmitter receptors and systems; and many other pathways that are highly conserved in wildlife and humans, and which can be modeled in laboratory in vitro and in vivo models. Furthermore, EDCs represent a broad class of molecules such as organochlorinated pesticides and industrial chemicals, plastics and plasticizers, fuels, and many other chemicals that are present in the environment or are in widespread use.
We make a number of recommendations to increase understanding of effects of EDCs, including enhancing increased basic and clinical research, invoking the precautionary principle, and advocating involvement of individual and scientific society stakeholders in communicating and implementing changes in public policy and awareness.
Discussion (DES and Fertility-specific)
General Introduction: the group of molecules identified as endocrine disruptors is highly heterogeneous and includes synthetic chemicals used as industrial solvents/lubricants and their byproducts [polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), dioxins], plastics [bisphenol A (BPA)], plasticizers (phthalates), pesticides [methoxychlor, chlorpyrifos, dichlorodiphenyltrichloroethane (DDT)], fungicides (vinclozolin), and pharmaceutical agents [diethylstilbestrol (DES)].
Reproduction: in the adult female, the first evidence of endocrine disruption was provided almost 40 yr ago through observations of uncommon vaginal adenocarcinoma in daughters born 15–22 yr earlier to women treated with the potent synthetic estrogen DES during pregnancy. Subsequently, DES effects and mechanisms have been substantiated in animal models. Thus, robust clinical observations together with experimental data support the causal role of DES in female reproductive disorders. However, the link between disorders such as premature pubarche and EDCs is so far indirect and weak, based on epidemiological association with both IUGR and ovulatory disorders. The implications of EDCs have been proposed in other disorders of the female reproductive system, including disorders of ovulation and lactation, benign breast disease, breast cancer, endometriosis, and uterine fibroids.
In the case of DES, there are both human and experimental observations indicating heritability.
Premature ovarian failure, decreased ovarian reserve, aneuploidy, granulosa steroidogenesis: interestingly, mice exposed in utero to DES, between d 9–16 gestation, have a dose-dependent decrease in reproductive capacity, including decreased numbers of litters and litter size and decreased numbers of oocytes (30%) ovulated in response to gonadotropin stimulation with all oocytes degenerating in the DES-exposed group, as well as numerous reproductive tract anatomic abnormalities. In women with in utero exposure to DES, Hatch et al reported an earlier age of menopause between the 43–55 yr olds, and the average age of menopause was 52.2 yr in unexposed women and 51.5 yr in exposed women. The effect of DES increased with cumulative doses and was highest in a cohort of highest in utero exposure during the 1950s. These observations are consistent with a smaller follicle pool and fewer oocytes ovulated, as in DES-exposed mice after ovulation induction.
Reproductive tract anomalies: disruption of female reproductive tract development by the EDC DES is well documented. A characteristic T-shaped uterus, abnormal oviductal anatomy and function, and abnormal cervical anatomy are characteristic of thisin utero exposure, observed in adulthood, as well as in female fetuses and neonates exposed in utero to DES. Some of these effects are believed to occur through ERα and abnormal regulation of Hox genes. Clinically, an increased risk of ectopic pregnancy, preterm delivery, miscarriage, and infertility all point to the devastating effect an endocrine disruptor may have on female fertility and reproductive health. It is certainly plausible that other EDCs with similar actions as DES could result in some cases of unexplained infertility, ectopic pregnancies, miscarriages, and premature deliveries. Although another major health consequence of DES exposurein utero was development of rare vaginal cancer in DES daughters, this may be an extreme response to the dosage of DES or specific to pathways activated by DES itself. Other EDCs may not result in these effects, although they may contribute to the fertility and pregnancy compromises cited above. Of utmost importance clinically is the awareness of DES exposure (and perhaps other EDC exposures) and appropriate physical exam, possible colposcopy of the vagina/cervix, cervical and vaginal cytology annually, and careful monitoring for fertility potential and during pregnancy for ectopic gestation and preterm delivery.
Endometriosis is an estrogen-dependent gynecological disorder associated with pelvic pain and infertility. There are suggestive animal data of adult exposure to EDCs and development of or exacerbation of existing disease, and there is evidence that in utero exposure in humans to DES results in an increased relative risk = 1.9 (95% confidence interval, 1.2–2.8).
Environmental estrogens effects on the prostate: DES exposure is an important model of endocrine disruption and provides proof-of-principle for exogenous estrogenic agents altering the function and pathology of various end-organs. Maternal usage of DES during pregnancy resulted in more extensive prostatic squamous metaplasia in human male offspring than observed with maternal estradiol alone. Although this prostatic metaplasia eventually resolved during postnatal life, ectasia and persistent distortion of ductal architecture remained. These findings have led to the postulation that men exposed in utero to DES may be at increased risk for prostatic disease later in life, although the limited population studies conducted to date have not identified an association. Nonetheless, several studies with DES in mouse and rat models have demonstrated significant abnormalities in the adult prostate, including increased susceptibility to adult-onset carcinogenesis after early DES exposures. It is important to note that developmental exposure to DES, as with other environmental estrogens, has been shown to exhibit a biphasic dose- response curve with regard to several end-organ responses, and this has been shown to be true for prostatic responses as well. Low-dose fetal exposure to DES or BPA (see full study) resulted in larger prostate size in adulthood compared with controls, an effect associated with increased levels of prostatic ARs. This contrasts with smaller prostate sizes, dysplasia, and aging- associated increases in carcinogenesis found after perinatal high-dose DES exposures as noted above. This differential prostatic response to low vs. high doses of DES and other EDCs must be kept in mind when evaluating human exposures to EDCs because the lack of a response at high doses may not translate into a lack of negative effects at low, environmentally relevant doses of EDCs.
Linking basic research to clinical practice: it should be clear from this Scientific Statement that there is considerable work to be done. A reconciliation of the basic experimental data with observations in humans needs to be achieved through translation in both directions, from bench to bedside and from bedside (and populations) to bench. An example of how human observation and basic research have successfully converged was provided by DES exposure in humans, which revealed that the human syndrome is faithfully replicated in rodent models. Furthermore, we now know that DES exposure in key developmental life stages can have a spectrum of effects spanning female reproduction, male reproduction, obesity, and breast cancer. It is interesting that in the case of breast cancer, an increased incidence is being reported now that the DES human cohort is reaching the age of breast cancer prevalence. The mouse model predicted this outcome 25 yr before the human data became available. In the case of reproductive cancers, the human and mouse data have since been confirmed in rats, hamsters, and monkeys. This is a compelling story from the perspective of both animal models and human exposures on the developmental basis of adult endocrine disease.
Prevention and the “precautionary principle”: although more experiments are being performed to find the hows and whys, what should be done to protect humans? The key to minimizing morbidity is preventing the disorders in the first place. However, recommendations for prevention are difficult to make because exposure to one chemical at a given time rarely reflects the current exposure history or ongoing risks of humans during development or at other life stages, and we usually do not know what exposures an individual has had in utero or in other life stages.
In the absence of direct information regarding cause and effect, the precautionary principle is critical to enhancing reproductive and endocrine health. As endocrinologists, we suggest that The Endocrine Society actively engages in lobbying for regulation seeking to decrease human exposure to the many endocrine-disrupting agents. Scientific societies should also partner to pool their intellectual resources and to increase the ranks of experts with knowledge about EDCs who can communicate to other researchers, clinicians, community advocates, and politicians.
Fertility and Ovarian Function in High-Dose Estrogen-Treated Tall Women, National Institutes of Health, NCBI PubMed PMID 21289262, 2011 Feb 2. Full text: The Endocrine Society, dx.doi.org/10.1210/jc.2010-2244, February 02, 2011.
High-dose estrogen treatment to reduce final height of tall girls has been shown to interfere with fertility. Ovarian function has not been studied. We therefore evaluated fertility and ovarian function in tall women who did or did not receive such treatment in adolescence.
This was a retrospective cohort study of 413 tall women aged 23-48 yr, of whom 239 women had been treated. A separate group of 126 fertile, normoovulatory volunteers aged 22-47 yr served as controls.
Fertility was assessed in 285 tall women (157 treated, 128 untreated) who had attempted to conceive. After adjustment for age, treated women were at increased risk of experiencing subfertility [odds ratio (OR) 2.29, 95% confidence interval (CI) 1.38-3.81] and receiving infertility treatments (OR 3.44, 95% CI 1.76-6.73). Moreover, fecundity was notably affected because treated women had significantly reduced odds of achieving at least one live birth (OR 0.26, 95% CI 0.13-0.52). Remarkably, duration of treatment was correlated with time to pregnancy (r = 0.23, P = 0.008). Ovarian function was assessed in 174 tall women (119 treated, 55 untreated). Thirty-nine women (23%) exhibited a hypergonadotropic profile. After adjusting for age category, treated women had significantly higher odds of being diagnosed with imminent ovarian failure (OR 2.83, 95% CI 1.04-7.68). Serum FSH levels in these women were significantly increased, whereas antral follicle counts and serum anti-Müllerian hormone levels were decreased.
High-dose estrogen-treated tall women are at risk of subfertility in later life. Their fecundity is significantly reduced. Treated women exhibit signs of accelerated ovarian aging with concomitant follicle pool depletion, which may be the basis of the observed subfertility.
We evaluated fertility and ovarian function in tall women who did or did not receive high-dose estrogen treatment in adolescence. Our results indicate that treated women experience more difficulties getting pregnant compared with untreated women and more often receive infertility treatments. We show for the first time that abnormal serum levels of hormones related to the hypothalamus-pituitary-gonadal axis, especially FSH, may be involved in the observed subfertility.
First we studied fertility of treated women, which was significantly reduced compared with untreated women. Fifty-six percent of treated women conceived their first pregnancy within 12 months of unprotected intercourse. As a consequence, 43% of treated women visited a doctor because of fertility problems and 28% required some form of infertility treatment. More importantly, we observed a significantly reduced chance of achieving a live birth. At the time of study almost one third of the treated women were suffering from involuntary childlessness for a median of 40 months. This is unexpected in light of earlier findings indicating only a slight reduction in the probability of eventually having a live birth. This may be explained by the fact that we studied fertility only in women who had attempted to conceive, which we believe better represents the women at risk of involuntary childlessness. Our time to pregnancy data are self-reported and may be confounded by recall bias. However, we believe that our conclusions are not affected by such bias because we also assessed fertility based on data such as having received infertility treatments, which is not prone to recall bias and showed similar results.
We also studied the effects of treatment within treated women only. We found that although age at initiation of treatment was not associated with outcome, duration of treatment was significantly correlated with time to pregnancy. Women with a TTP of more than 12 months had on average been treated for 3 months longer. Although the effect of oral contraceptives on subsequent fertility has not been extensively studied, one study has reported an effect of estrogen dose on conception delay. Recent studies did not find such an association, possibly because low-dosage estrogen pills were used. Because of no variation in dosage in our population, we were unable to study the effect of estrogen dose more specifically.
Next, we analyzed ovarian function to study possible causes of the reduced fertility. Ovarian function was categorized based on serum gonadotropin levels. We observed an increased frequency of women with a hypergonadotropic profile. Our principal finding is that treated women are at increased risk of being diagnosed with IOF compared with untreated women. To account for normal changes in ovarian function in the late reproductive stages, treated and untreated women were divided into two age categories for the analysis of ovarian function. Taking these age categories into account, the odds of IOF diagnosis in treated women was almost 3-fold higher than in untreated women. Although ovarian function was primarily categorized based on serum FSH levels, the diagnosis of IOF was also supported by other parameters. We observed significantly decreased antral follicle counts and serum AMH levels in women with IOF as compared with normogonadotropic tall women. Serum AMH is currently the best marker for primordial follicle pool size because in the ovary it is expressed in granulose cells of follicles that have undergone recruitment but have not yet been selected for dominance. In addition, AMH plays an important role in regulating folliculogenesis because it is involved in determining the individual FSH threshold of early antral follicles. In addition, we believe some other possible pathologies, such as PCOS, can now be excluded as a potential cause of the observed infertility because of prevalence levels similar to the estimated population frequency.
Finally, we compared our results to a cohort of healthy fertile controls. Parameters of ovarian function were comparable between normogonadotropic tall women and these controls. Comparison with hypergonadotropic women confirmed that parameters of ovarian function in these women are indicative of accelerated follicle pool depletion.
The results of our study do not only validate earlier epidemiological findings from an Australian study but may also provide physicians with clinically useful information aiding in the diagnosis and treatment of estrogen-treated tall women with fertility problems. To our best knowledge, this is the first report establishing ovarian dysfunction in these women. It seems that follicle dynamics have changed in that respect that a considerable number of these women seem to suffer from accelerated follicle loss being reflected by increased serum FSH levels along with decreased AMH levels as well as low antral follicle counts. Hence, it seems that tall women who have been treated with estrogens in the past are prone to lose their reproductive capacity earlier in life, and they should be counseled accordingly.
In conclusion, we evaluated fertility and ovarian function in later life of tall women who did or did not receive high-dose estrogen treatment in adolescence. We found that estrogen-treated women experienced more difficulties conceiving and more often received medical treatment for infertility compared with untreated women. Treated women had a decreased chance of achieving at least one live birth. We observed a possible dose-response relationship because duration of treatment was correlated with time to pregnancy. Finally, we showed that treated women were at increased risk of being diagnosed with IOF. They exhibit signs of accelerated ovarian aging with concomitant follicle pool depletion, which may be the basis of the observed subfertility. However, the mechanism behind this accelerated follicle loss by high-dose estrogen treatment remains unknown and requires future research.
Reproductive performance of women with müllerian anomalies, Current opinion in obstetrics & gynecology, NCBI PubMed PMID: 17495638, 2007 Jun.
PURPOSE OF REVIEW
This review discusses current diagnostic techniques for müllerian anomalies, reproductive outcome data, and management options in reproductive-age women.
Multiple retrospective studies have investigated reproductive outcomes with müllerian anomalies, but few current prospective studies exist. Uterine anomalies are associated with normal and adverse reproductive outcomes such as recurrent pregnancy loss and preterm delivery, but not infertility. Furthermore, unicornuate, didelphic, bicornuate, septate, arcuate, and diethylstilbestrol-exposed uteri have their own reproductive implications and associated abnormalities. Common presentations of müllerian anomalies and current diagnostic techniques are reviewed. Surgical intervention for müllerian anomalies is indicated in women with pelvic pain, endometriosis, obstructive anomalies, recurrent pregnancy loss, and preterm delivery. Although surgery for most uterine anomalies is a major intervention, the uterine septum is preferentially managed with a hysteroscopic procedure. Several recent studies and review articles discuss management of the septate uterus in asymptomatic women, infertile women, and women with a history of poor reproductive outcomes. Current assessment of reproductive outcomes with uterine anomalies and management techniques is warranted.
Müllerian anomalies, especially uterine anomalies, are associated with both normal and adverse reproductive outcomes, and management in infertile women remains controversial.
Menstrual and reproductive characteristics of women whose mothers were exposed in utero to diethylstilbestrol (DES), International journal of epidemiology, NCBI PubMed PMID: 16723367, 2006 Aug.
Full text: Oxford Journals, Medicine & Health, International Journal of Epidemiology, Volume 35, Issue 4Pp. 862-868, doi: 10.1093/ije/dyl106, August 2006.
In women, prenatal exposure to diethylstilbestrol (DES) is associated with adult reproductive dysfunction. The mouse model, which replicates many DES outcomes, suggests DES causes epigenetic alterations, which are transmissable to daughters of prenatally exposed animals. We report menstrual and reproductive characteristics in a unique cohort comprising daughters of women exposed prenatally to DES.
Menstrual and reproductive outcomes and baseline characteristics were assessed by mailed questionnaire in 793 women whose mothers had documented information regarding in utero DES exposure.
Mean age at menarche was 12.6 years in both groups,
but daughters of the exposed women attained menstrual regularization later (mean age of 16.2 years vs. 15.8 years; P = 0.05),
and were more likely to report irregular menstrual periods, odds ratio (OR) = 1.54 [95% confidence interval (95% CI 1.02–2.32)].
A possible association between mothers’ DES exposure and daughters’ infertility was compatible with chance, age, and cohort adjusted OR = 2.19 (95% CI 0.95–5.07). We found limited evidence that daughters of the exposed had more adverse reproductive outcomes, but daughters of exposed women had fewer live births (1.6) than the unexposed (1.9) (P = 0.005).
The high risk of reproductive dysfunction seen in women exposed to DES in utero was not observed in their daughters, but most women in our cohort have not yet attempted to start their families, and further follow-up is needed to assess their reproductive health. Our findings of menstrual irregularity and possible infertility in third-generation women are preliminary but compatible with speculation regarding transgenerational transmission of DES-related epigenetic alterations in humans.
Excerpts and Discussion
The mean birth weight of offspring appeared lower in daughters of the exposed than in the unexposed (3374.2 g vs. 3540.5 g) (P = 0.08).
Our data indicate that DES Grand Daughters attain menstrual regularity at a slightly later age than daughters of the unexposed and are more likely to experience menstrual irregularity.
Our study suggests that infertility may also be more frequent in the DES Grand Daughters, and that DES exposure may exacerbate age-related infertility, a possibility compatible with findings in men who were exposed to DES in utero. The proportion of third-generation women affected by infertility (5%) in this study was far lower than that observed in the (second) generation of women exposed in utero to DES (30%).
In the prenatally exposed women, infertility is primarily due to anatomic anomalies of the uterus or fallopian tubes; other diagnoses, including hormonal/ovulatory problems, play a less striking role. Anatomic and tissue anomalies were not observed in a study of 28 third-generation women, but the number of participants was too small to rule out a low prevalence, and some irregularities (e.g. uterine, tubal) might not be evident on physical examination.
Further follow-up is needed to confirm the possible infertility in the third-generation women, and to evaluate specific diagnoses, which may provide insight into DES-related mechanisms.
It is well-known that women exposed to DES in utero have increased pregnancy complications and adverse birth outcomes, including ectopic pregnancy, pregnancy loss, and preterm delivery. Our data are not conclusive regarding adverse pregnancy outcomes in third-generation women, although daughters of the exposed had somewhat fewer live born children and babies of slightly lower average birth weight. Further follow-up will be essential to assess reproductive outcomes as more of the third-generation women enter their reproductive years.