Clomid administration to pregnant rats causes abnormalities of the reproductive tract in offspring and mothers

Post-Conceptional Exposure to Clomiphene Citrate and Congenital Malformations: A Cohort Study

BACKGROUND

Clomiphene citrate is an ovulation inductor for which inadvertent post-conceptional exposures may occur in early pregnancy. In preclinical studies, post-conceptional exposures showed a teratogenic effect in different species. In humans, to date, little is known about the outcomes of inadvertently post-conceptionally exposed pregnancies.

OBJECTIVES

The objectives of our study were to assess the association between post-conceptional exposures to clomiphene citrate and major and minor congenital malformations in the offspring.

METHODS

A retrospective cohort study of prospectively ascertained cases was undertaken, based on clinical data from the Centre de Référence sur les Agents Tératogènes (CRAT), Paris, France. Women with post-conceptional exposure to clomiphene citrate (n = 309), and unexposed pregnant women (n = 1236, 1:4 ratio) with prospectively collected data, known pregnancy outcome and delivery date prior to 01/02/2022, were matched by calendar year. An adjudication committee classified major and minor congenital malformations according to the EUROCAT (European Registration of Congenital Anomalies and Twins) classification.

RESULTS

Among post-conceptional exposed women, no increased risk of major malformation was found (crude relative risk = 0.64, 95% confidence interval 0.19-2.15) as compared to unexposed women. Three major and ten minor congenital malformations were reported in the exposed group. An increased risk of minor malformations was found (crude relative risk = 4.05, 95% confidence interval 1.70-9.64) although there was no specific clinical pattern.

CONCLUSIONS

Post-conceptional exposure to clomiphene citrate was not associated with an increased risk of major congenital malformations. Given potential confounding and information biases, the results about minor malformations should be interpreted with caution as no specific clinical pattern was identified.

Clomiphene Citrate Administered in Periconception Phase Causes Fetal Loss and Developmental Impairment in Mice

Clomiphene citrate is a common treatment for ovulation induction in subfertile women, but its use is associated with elevated risk of adverse perinatal outcomes and birth defects. To investigate the biological plausibility of a causal relationship, this study investigated the consequences in mice for fetal development and pregnancy outcome of periconception clomiphene citrate administration at doses approximating human exposures. A dose-dependent adverse effect of clomiphene citrate given twice in the 36 hours after mating was seen, with a moderate dose of 0.75 mg/kg sufficient to cause altered reproductive outcomes in 3 independent cohorts. Viable pregnancy was reduced by 30%, late gestation fetal weight was reduced by 16%, and ∼30% of fetuses exhibited delayed development and/or congenital abnormalities not seen in control dams, including defects of the lung, kidney, liver, eye, skin, limbs, and umbilicus. Clomiphene citrate also caused a 30-hour average delay in time of birth, and elevated rate of pup death in the early postnatal phase. In surviving offspring, growth trajectory tracking and body morphometry analysis at 20 weeks of age showed postweaning growth and development similar to controls. A dysregulated inflammatory response in the endometrium was observed and may contribute to the underlying pathophysiological mechanism. These results demonstrate that in utero exposure to clomiphene citrate during early pregnancy can compromise implantation and impact fetal growth and development, causing adverse perinatal outcomes. The findings raise the prospect of similar iatrogenic effects in women where clomiphene citrate may be present in the periconception phase unless its use is well-supervised.

Safety assessment of clomiphene: a real-world pharmacovigilance analysis from the Food and Drug Administration adverse event reporting system

BACKGROUND

Clomiphene is widely used for the treatment of anovulatory infertility, yet there remain many unrecognized adverse events (AEs). The objective of this study is to provide a comprehensive overview of the safety profile of clomiphene.

METHODS

The data were derived from the first quarter of 2004 to the third quarter of 2023 from the Food and Drug Administration Adverse Event Reporting System (FAERS) database. The detection of new AE signals involved the use of four algorithms: reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian confidence propagation neural network (BCPNN), and empirical Bayesian geometric mean (EBGM).

RESULTS

A total of 16,677,289 AE reports were acquired from the FAERS database, and there were 2,620 AEs specifically reported in 720 patients following clomiphene use. The AEs encompassed 102 preferred terms (PTs) across 24 system organ classes (SOCs). Some new AEs were identified, including conjoined twins (0.5%), Potter's syndrome (0.3%), genitalia external ambiguous (0.3%), esophageal atresia (0.6%), and anal atresia (0.3%).

CONCLUSIONS

Although the majority of AEs aligned with the drug instruction, some new AE signals such as conjoined twins and genitalia external ambiguous were not captured. Well-designed studies are required to demonstrate the safety of clomiphene.

Maternal tamoxifen exposure leads to abnormal primordial follicle assembly

Tamoxifen (TAM) is an accredited drug used for treatment and prevention of breast cancer. Due to the long-term taking and the trend for women to delay childbearing, inadvertent conception occasionally occurs during TAM treatment. To explore the effects of TAM on a fetus, pregnant mice at gestation day 16.5 were orally administrated with different concentrations of TAM. Molecular biology techniques were used to analyze the effects of TAM on primordial follicle assembly of female offspring and the mechanism. It was found that maternal TAM exposure affected primordial follicle assembly and damaged the ovarian reserve in 3 dpp offspring. Up to 21 dpp, the follicular development had not recovered, with significantly decreased antral follicles and decreased total follicle number after maternal TAM exposure. Cell proliferation was significantly inhibited; however, the cell apoptosis was induced by maternal TAM exposure. Epigenetic regulation was also involved in the process of TAM induced abnormal primordial follicle assembly. The changed levels of H3K4me3, H3K9me3, and H3K27me3 presented the function of histone methylation in the regulation of the effects of maternal TAM exposure on the reproduction of female offspring. Moreover, the changed level of RNA m6A modification and the changed expression of genes related to transmethylation and demethylation proved the role of m6A in the process. Maternal TAM exposure led to abnormal primordial follicle assembly and follicular development by affecting cell proliferation, cell apoptosis, and epigenetics.

Potential Teratogenic Effects of Clomiphene Citrate

Clomiphene citrate (CC) is the oldest drug used to regulate the process of ovulation. Considering the great use of CC over the last 40 years, it is important to understand the possible risks associated with its use. The aim of this review was to evaluate the possible teratogenic effects of CC, analyzing results obtained from animal and human studies. The pharmacokinetics of CC and possible mechanisms involved in teratogenesis are examined. Fetal exposure to CC is possible due to the long half-life of CC and its metabolites. Alarming data have emerged from animal studies, although controversial results come from human studies. There is some evidence regarding a possible association of CC exposure and fetal malformations, mainly neural tube defects and hypospadias, which would require further investigation in order to allow safer use of this useful drug.

Novel antioestrogens

Recently described 7α-alkylamide analogues of oestradiol, exemplified by ICI 164,384, have the pharmacological characteristics of pure antioestrogens. ICI 164,384 is completely free of oestrogenic activity in rodents and blocks the trophic actions of exogenous and endogenous oestradiol and of partial agonist antiooestrogens like tamoxifen. In addition, ICI 164,384 is peripherally selective, producing complete involution of the uterus without affecting LH secretion in intact female rats.

In MCF-7 oestrogen-responsive, human breast cancer cells ICI 164,384 is a more potent and effective inhibitor of cell growth than tamoxifen. This difference in efficacy is reflected by a greater reduction in the proportion of cells continuing DNA synthesis in ICI 164,384-treated cultures than in tamoxifen-treated cells. This observation implies that a pure antioestrogen may provide more effective therapy of breast cancer but this will have to be demonstrated in clinical studies.

Oral administration of clomiphene to neonatal rats causes reproductive tract abnormalities

Oral administration of clomiphene at 2, 4, or 8 mg/kg to 4-day-old rats caused multiple histopathological abnormalities of the reproductive tract in both male and female animals. No histopathological abnormalities were observed in 30-day-old male rats at any dose examined. In contrast, 30-day-old females showed hypertrophy of the myometrium at all doses examined, and hypertrophy of the luminal or glandular epithelium, and dilatation of the uterine lumen were observed in the highest dose group. In post-pubertal rats, histopathologically marked changes were observed in the testes and epididymides in males, and in the ovaries and uterus in females in the highest dose group. In addition, relative weight of male reproductive organs in the highest dose group was decreased as compared with that in the controls. These results suggested that early neonatal exposure to clomiphene induced marked reproductive tract abnormalities in males after puberty, as well as in females.

Short- and long-term effects of ovulation induction

Ovulation induction using clomiphene citrate, gonadotropins, and gonadotropin-releasing hormone is reviewed. The short- and long-term consequences of these therapies are discussed in detail.

Reproductive effects of prenatal exposure to 5-bromo-2'-deoxyuridine on male rats

5-Bromo-2'-deoxyuridine (BrdU) was administered intraperitoneally to Sprague-Dawley rats at doses of 12.5, 25, 50, or 100 mg/kg/d on days 9 through 15 of gestation, and at 50 or 100 mg/kg/d on days 16 through 20 of gestation. Dams were allowed to deliver naturally and the numbers of live and dead pups were recorded. Male offspring were allowed to mature and then cohabited with untreated female rats for assessment of reproductive performance. Dam body weight gain during pregnancy and lactation periods was not reduced by the treatment with BrdU. Dams treated with 50 and 100 mg BrdU/kg on days 9 through 15 of gestation had litters with decreased survival rates. The male offspring from dams treated with 25, 50, and 100 mg BrdU/kg on days 9 through 15 of gestation had reduced body weights over the course of the entire study. A dose-related decrease in copulation and fertility rates was found in the male offspring of dams treated on days 9 through 15 of gestation, while no significant decrease in those rates were found in the male offspring of dams treated on days 16 through 20 of gestation. Neither histopathologic examination of testes nor sperm examination indicated the cause of the impaired fertility in the male offspring from dams treated with BrdU on days 9 through 15 of gestation. All of the male offspring of dams treated with 100 mg BrdU/kg on days 9 through 15 of gestation failed to copulate, and some of the male offspring of dams treated with 50 mg BrdU/kg on days 9 through 15 of gestation did not form copulatory plugs or formed very small plugs. Dilatation of the lateral ventricles and cysts in the pars distalis of the pituitary were observed in all of the male offspring of dams treated with 100 mg BrdU/kg on days 9 through 15 of gestation. The impaired fertility of the male offspring of dams treated prenatally with BrdU may have resulted from BrdU exposure effects on central nervous system action such as loss of libido and from failure to form proper copulatory plugs, rather than the direct effects of BrdU on the male reproductive organs.

Adverse effects of fertility drugs

Ovulation-induction agents are commonly used in the treatment of infertility in patients with or without ovulatory disturbances. These agents include clomifene, bromocriptine, gonadotrophin preparations and gonadotrophin-releasing hormone (GnRH) and its analogues. Each agent is associated with its own specific adverse effects. Although many of these adverse effects are benign and self-limited, some, in particular those effects associated with gonadotrophins, may be life-threatening. Commonly noted adverse effects encountered with the use of pharmacological agents to treat infertility include the following. Clomifene has been associated with hot flushes, multiple gestation, visual disturbances, cervical mucus abnormalities and luteal phase deficiency. Similarly, most of the adverse symptoms associated with bromocriptine are short-lived, such as nausea and postural hypotension. On the other hand, gonadotrophin therapy, even when used appropriately, may lead to the ovarian hyperstimulation syndrome (which is occasionally life-threatening) and a high incidence of multiple gestation. Pulsatile GnRH therapy maybe accompanied by similar adverse effects to those of gonadotrophins, but with a far lower incidence. With regards to the long term safety of these medications, the relationship between fertility drugs and epithelial ovarian cancer is controversial, and causality has yet to be proven. Indeed, a working knowledge of the many adverse effects associated with these medications is essential to any physician prescribing ovulation induction agents, in order to ensure maximum patient safety, compliance and understanding.

Therapeutic potential of pure antioestrogens in the treatment of breast cancer

Novel 7 alpha-analogues of 17 beta-oestradiol like ICI 164,384, differ from all antioestrogens described previously in being entirely free of partial agonist activity. In adult rats, ICI 164,384 blocks completely the stimulatory effects of endogenous or exogenous oestrogens and produces a castration-like involution of the uterus without affecting the hypothalamic-pituitary-ovarian axis. If analogous effects were achieved in patients, peripherally-selective complete oestrogen withdrawal would occur, which presents a novel pharmacological option not achieved by any current treatment. Studies with human breast cancer cells showed that ICI 164,384 reduced to a greater extent than did tamoxifen, the mitotic fraction. This difference may reflect a synergistic stimulatory interaction between serum growth factors like insulin, and the partial agonist effect of tamoxifen which is not seen with ICI 164,384. In long-term culture in the presence of ICI 164,384 no resistant cell lines developed, as has been observed previously in studies with tamoxifen. Pure antioestrogens might thus have a further therapeutic advantage over partial agonists like tamoxifen in reducing the probability of treatment failure due to the regrowth of tumours from resistant cells.

Pharmacodynamic and biological effects of anti-estrogens in different models

The biological response to anti-estrogens is very variable and depends on the animal species considered, the target organ, the parameter studied, and the experimental conditions. Anti-estrogens can bind specifically, (1) to the estrogen receptor, (2) to the typical anti-estrogen specific binding site, and (3) to low density lipoproteins in the plasma. Using a monoclonal antibody against the estrogen receptor, different immunological characteristics of the anti-estrogen-receptor complex can be observed. This difference could explain some of the different biological effects. Studies using different human mammary cancer cell lines (hormone-dependent) show that anti-estrogens are active in decreasing cell proliferation. Also, anti-estrogens can block proteins specifically produced by these cells. Some of these proteins could act as growth or inhibitory factors. Estrogen sulfates are the main precursors of estradiol in breast tissues and this conversion is significantly decreased by anti-estrogens. It is accepted that the main pathway of action of anti-estrogens is through the estrogen receptor, but recent information suggests the possibility that this is not the only step in the mechanism of action of anti-estrogens.

Teratogenic effects of clomiphene, tamoxifen, and diethylstilbestrol on the developing human female genital tract

The potential estrogenicity and teratogenicity of triphenylethylene antiestrogens were examined in 54 genital tracts isolated from 4- to 19-week-old human female fetuses and grown for 1 to 2 months in untreated athymic nude mice or host mice treated by subcutaneous pellet with the antiestrogens clomiphene and tamoxifen or the synthetic estrogen diethylstilbestrol (DES). In specimens grown to a gestational age equivalent of 15 weeks or less, the vagina and urogenital sinus were lined by an immature squamous epithelium, which were similar in both drug-treated and untreated specimens. Proliferation and maturation of the squamous vaginal epithelium were observed in specimens treated with clomiphene, tamoxifen, or DES only when grown to a gestational age equivalent of 16 weeks or more. Formation of endometrial and cervical glands proceeded in 87 per cent (13 of 15) of control specimens grown to a gestational age equivalent of 13 weeks or more in untreated hosts. By contrast, age-matched drug-treated specimens contained glands in only 44 per cent (12 of 27) of specimens. In the developing uterine corpus of untreated controls, the uterine mesenchyme segregated into inner (endometrial stroma) and outer (myometrial) layers; whereas in drug-treated specimens, condensation and segregation of the mesenchyme were greatly impaired. The fallopian tube was also affected by clomiphene and tamoxifen (and to a lesser extent by DES) in that its epithelium was hyperplastic and disorganized. The complex mucosal plications characteristic of the fallopian tube were also distorted in drug-treated specimens. These results emphasize the heretofore unrecognized estrogenicity and potential teratogenicity of triphenylethylene antiestrogens on the developing human genital tract and emphasize the need for caution to prevent inadvertent exposure of the developing fetus to these compounds.

Anti-estrogens in fetal and newborn target tissues

The antagonistic effects of progesterone and of the anti-estrogens, tamoxifen and nafoxidine, to estrogen responses were studied in the target tissues of fetal and newborn guinea pigs. In the fetal uterus, progesterone inhibits the stimulatory effect provoked by estradiol on uterine growth, on progesterone receptor and on the acetylation of nuclear histones. Progesterone also blocks the synthesis of new progesterone receptor protein in organ culture. Tamoxifen or nafoxidine (1 or 10 mg/kg/day injected to the mother for 3 days) provoke a uterotrophic effect similar to that of estradiol (1 mg/kg/day injected to the mother for 3 days) but these anti-estrogens have a limited effect on the progesterone receptor. Tamoxifen given together with estradiol antagonizes the effect of the estrogen on the acetylation of histones but the anti-estrogens do not block the effect of estradiol on uterine growth. Histological studies show that both estradiol and tamoxifen provoke a dramatic hypertrophic and hyperplastic effect particularly in the uterine epithelium. In the newborn uterus (6-day old), tamoxifen (s.c. injection of 0.6 micrograms/g body weight) and estradiol (injection of 30 ng/g body weight) provoke a similar uterotrophic effect and both have a limited effect on the progesterone receptor. In the fetal thymus estradiol provokes a selective decrease in the larger and actively proliferating lymphoid cells of the cortical zone. Tamoxifen has a similar effect but to a much lesser extent than estradiol. On the other hand, tamoxifen antagonizes the effect of estradiol on this fetal tissue. It is concluded that during fetal life progesterone antagonizes the effect of estradiol but tamoxifen can act as an agonist or an antagonist of estrogen action which is a function of the type of response or organ considered.

The estrogenic effects of clomiphene during the neonatal period in the rat

The ability of clomiphene and its isomers to cause estrogenic responses during the neonatal period in the rat was examined. Rats were injected s.c. with clomiphene (CL), zuclomiphene (ZUC) or enclomiphene (ENC) on days 1,3, and 5 of life and the stimulation of the reproductive tract and estrogen receptor binding was observed. Uterine weight and DNA content were increased significantly by day 7 in animals treated with clomiphene or zuclomiphene. Uterine epithelial hypertrophy was present in all groups by day 10 and hyperplasia was present in the animals treated with ZUC and CL. The time of vaginal opening was greatly accelerated in all drug treated groups with the earliest day of opening occurring on day 7. Ovarian hemorrhage and blood in the periovarian sac occurred between days 12-14 and continued to be present through day 25. Drug treatment caused the estrogen receptor to accumulate in the nuclear fraction of the uterus and to be depleted from the cytosol fraction. We conclude that clomiphene administered to neonatal rats causes estrogenic stimulation of the reproductive tract in a fashion similar to other estrogens. This stimulation may account for the reproductive tract abnormalities which develop in rats treated with those drugs during the neonatal period.

Characterization of estrogen binding in uterine cytosol from the fetal rhesus monkey

Cytosol receptor binding of 17 beta-estradiol was demonstrated in the uterus of the late-gestation, fetal rhesus monkey. Sucrose density gradient analysis performed in low-ionic strength buffer indicated a binding component with a sedimentation coefficient of 6-7 S. Under high-ionic strength conditions, the component shifted to a sedimentation coefficient of approximately 4 S. The specificity of the receptor for estrogens was indicated by inhibition of [3H]estradiol binding by both natural and synthetic estrogen competitors, but not by progesterone. Saturation analysis indicated a high degree of nonspecific binding with saturation of specific binding occurring at 2-3 nM. Computer-assisted Scatchard analysis of the data resolved a one-receptor model having a limited number of binding sites and an apparent dissociation constant of 10(-10) M. The interaction of estrogens with the fetal uterus and the cellular mechanisms which permit this interaction are discussed in relation to the development of models for extrapolation to the human.

Heterotopic columnar epithelium and adenosis in the vagina of the mouse after neonatal treatment with clomiphene citrate

Physiologically, the epithelium of the mouse vagina undergoes conversion during early postnatal life from columnar to stratified squamous. A similar process in the human occurs in the late first and early second trimesters of pregnancy. The mouse vagina has been identified as a good developmental model of the human. Previous work in the mouse has shown that this process is affected by neonatal administration of diethylstilbestrol. We have administered diethylstilbestrol and clomiphene citrate to parallel groups of BALB/c neonatal mice. They were followed up to 24 weeks. In both groups, persistent columnar or heterotopic columnar epithelium, not seen in the control mice, was identified and associated with adenosis. This effect of diethylstilbestrol and clomiphene citrate appears to be similar to the biologic response to transplacental diethylstilbestrol in the human. After transplacental diethylstilbestrol, malignant vaginal tumors rarely develop. If clomiphene citrate, given to the human prior to pregnancy to induce ovulation or by inadvertence during pregnancy, were to circulate into the critical time of vaginal differentiation, a similar biologic potential may exist. The first situation seems to be unlikely. The second is of more concern.

Biochemical and estrogenic activity of some diethylstilbestrol metabolites and analogs in the mouse uterus

DES is metabolized to a number of compounds through a minimum of three main metabolic routes. These routes result in some inactivity of DES as an estrogen, but the majority appear to produce estrogenic by-products, which in some cases produce divergent in vivo and in vitro hormone activities. Therefore, if DES undergoes this type of metabolism, then large doses or repeated ingestion could produce a body burden of compounds with a wide range of hormonal activities possessing some possibly toxic or carcinogenic nature. It is apparent that these types of findings must also be considered when DES is used as an estrogenic test substance. The studies in this report have only attempted to ascertain the hormonal activity or these compounds and do not address the questions of their toxic or carcinogenic nature.

Structure and function of the fallopian tubes following exposure to diethylstilbestrol (DES) during gestation

The association between the use of diethylstilbestrol (DES) and vaginal and cervical adenocarcinoma and adenosis in the progeny was first reported by Herbst et al. in 1971. This progeny will reach a peak as far as reproduction is concerned in this decade. It is estimated that 2 million women may be involved to varying degrees. Changes in uterine and cervical contour and structure have been detailed. Thus DES exposure and anatomic changes in the Müllerian system have been documented. In this report 16 women in the reproductive age group who were exposed to DES in utero and presented with infertility are discussed. On workup for infertility they were found to have unique tubal morphologic features consisting of a foreshortened, convoluted tube with "withered" fimbria with a pinpoint os at laparoscopy. The diagnosis could not be made at the time of hysterosalpingogram. Three patients had surgery in an attempt to correct this condition; and in all cases the surgery was unsuccessful. No statistical data is offered as to epidemiologic factors or incidence rates, but the suspected increase in infertility and ectopic pregnancy rates in patients with DES exposure may corroborate these findings.