Is follicular atresia biphasic?

Recapitulating human ovarian aging using random walks

Mechanism(s) that control whether individual human primordial ovarian follicles (PFs) remain dormant, or begin to grow, are all but unknown. One of our groups has recently shown that activation of the Integrated Stress Response (ISR) pathway can slow follicular granulosa cell proliferation by activating cell cycle checkpoints. Those data suggest that the ISR is active and fluctuates according to local conditions in dormant PFs. Because cell cycle entry of (pre)granulosa cells is required for PF growth activation (PFGA), we propose that rare ISR checkpoint resolution allows individual PFs to begin to grow. Fluctuating ISR activity within individual PFs can be described by a random process. In this article, we model ISR activity of individual PFs by one-dimensional random walks (RWs) and monitor the rate at which simulated checkpoint resolution and thus PFGA threshold crossing occurs. We show that the simultaneous recapitulation of (i) the loss of PFs over time within simulated subjects, and (ii) the timing of PF depletion in populations of simulated subjects equivalent to the distribution of the human age of natural menopause can be produced using this approach. In the RW model, the probability that individual PFs grow is influenced by regionally fluctuating conditions, that over time manifests in the known pattern of PFGA. Considered at the level of the ovary, randomness appears to be a key, purposeful feature of human ovarian aging.

Could hormonal and follicular rearrangements explain timely menopause in unilaterally oophorectomized women?

STUDY QUESTION

Does unilateral oophorectomy modify the relationship between serum anti-Müllerian hormone (AMH) levels and antral follicle count (AFC)?

SUMMARY ANSWER

No altered 'per-ovary' and 'per-follicle' AMH production and antral follicle distribution was evident in unilaterally oophorectomized women compared to matched controls.

WHAT IS KNOWN ALREADY

The age of menopause onset is relatively unchanged in patients having undergone unilateral oophorectomy. Mechanisms that occur to preserve and maintain ovarian function in this context remain to be elucidated.

STUDY DESIGN, SIZE, DURATION

Forty-one infertile women, with no polycystic ovary syndrome (PCOS) and no endometriosis, aged 19-42 years old, having undergone unilateral oophorectomy (One Ovary group; average time since surgery: 23.8 ± 2.2 months) were retrospectively age-matched (±1 year) with 205 infertile women having two intact ovaries and similar clinical features (Control group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Serum AMH levels, 3-4 mm AFC, 5-12 mm AFC, and total AFC (3-12 mm) were assessed on cycle Day 3 in both groups. Hormonal and ultrasonographic measurements obtained from patients in the Control group (i.e. having two ovaries) were divided by two to be compared with measurements obtained from patients of the One Ovary group (i.e. having one single remaining ovary). To estimate per-follicle AMH production, we calculated the ratio between serum AMH levels over 3-4 mm AFC, 5-12 mm AFC, and total AFC (3-12 mm), and the strength of the correlation between serum AMH levels and total AFC. The main outcome measure was to assess Day 3 AMH/Day 3 AFC ratio and hormonal-follicular correlation.

MAIN RESULTS AND THE ROLE OF CHANCE

As expected, before correction, mean serum AMH levels (1.46 ± 0.2 vs 2.77 ± 0.1 ng/ml, P < 0.001) and total AFC (7.3 ± 0.6 vs 15.1 ± 0.4 follicles, P < 0.0001) were lower in the One Ovary group compared to the Control group, respectively. Yet, after correction, per-ovary AMH levels (1.46 ± 0.2 vs 1.39 ± 0.1 ng/ml) and total AFC (7.3 ± 0.6 vs 7.5 ± 0.2 follicles) values were comparable between the two groups. Consistently, per-follicle AMH levels (3-4 mm, 5-12 mm, and total) were not significantly different between the two groups (0.39 ± 0.05 vs 0.37 ± 0.02 ng/ml/follicle; 0.69 ± 0.12 vs 0.59 ± 0.05 ng/ml/follicle, and 0.23 ± 0.03 vs 0.19 ± 0.01 ng/ml/follicle; respectively). In addition, the prevalence of 3-4 mm follicles was comparable between the two groups (66.7% for One Ovary group vs 58.8% for Control group, respectively). Finally, the correlation between serum AMH levels and total AFC was similar for patients in the One Ovary group (r = 0.70; P < 0.0001) compared to those in the Control group (r = 0.68; P < 0.0001).

LIMITATIONS/REASONS FOR CAUTION

The retrospective character of the analysis might lead to potential bias.

WIDER IMPLICATIONS OF THE FINDINGS

The present investigation did not provide evidence of altered 'per-ovary' and 'per-follicle' AMH production and antral follicle distribution in unilaterally oophorectomized women compared to matched controls. Further studies are warranted to support the hypothesis that follicle-sparing mechanisms are clearly at stake in remaining ovaries after unilateral oophorectomy to explain their long-lasting function and timely menopausal onset.

STUDY FUNDING/COMPETING INTEREST(S)

The authors have no funding or competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

The evolutionary ecology of age at natural menopause: implications for public health

Evolutionary perspectives on menopause have focused on explaining why early reproductive cessation in females has emerged and why it is rare throughout the animal kingdom, but less attention has been given to exploring patterns of diversity in age at natural menopause. In this paper, we aim to generate new hypotheses for understanding human patterns of diversity in this trait, defined as age at final menstrual period. To do so, we develop a multilevel, interdisciplinary framework, combining proximate, physiological understandings of ovarian ageing with ultimate, evolutionary perspectives on ageing. We begin by reviewing known patterns of diversity in age at natural menopause in humans, and highlight issues in how menopause is currently defined and measured. Second, we consider together ultimate explanations of menopause timing and proximate understandings of ovarian ageing. We find that ovarian ageing is highly constrained by ageing of the follicle - the somatic structure containing the oocyte - suggesting that menopause timing might be best understood as a by-product of ageing rather than a facultative adaptation. Third, we investigate whether the determinants of somatic senescence also underpin menopause timing. We show that diversity in age at menopause can be, at least partly, explained by the genetic, ecological and life-history determinants of somatic ageing. The public health implications of rethinking menopause as the by-product rather than the catalyst of biological ageing are discussed.

The Attenuating Effect of the Intraovarian Bone Morphogenetic Protein 4 on Age-Related Endoplasmic Reticulum Stress in Chicken Follicular Cells

In the poultry, only less than 5% primordial follicles in the ovary can develop into the prehierarchical follicles (PHFs) leading to progressive development, ovulation, and egg formation. This low rate of recruitment indicates a huge potential for improvement of the laying performance. A great reduction in egg production is caused by aging with extensive follicular atresia. In this study, age-related changes in the laying performance and ovarian status were compared between the peak-lay (D280) and aged (D580) chickens. Subsequently, a cross coculture of PHFs and granulosa cells (GCs) from D280 or D580 hens was adopted to reveal the mechanism of declined follicle development. Results showed that persistent endoplasmic reticulum (ER) stress in GCs of the aged hens was accompanied with intensified apoptosis. Bone morphogenetic protein 4 (BMP4) secreted by GCs of PHFs in D280 hens was capable of relieving ER stress and improving follicular dominance for selection in D580 hens. During this action, BMP4 reduced free calreticulin (CALR, an ER marker) content and attenuated cell apoptosis in PHFs of D580 hens via the PERK-CHOP-BCL2/caspase3 or CALR-Ca²⁺-BCL2-caspase12 pathway. Furthermore, BMP4 prevented follicular atresia by promoting production of steroid hormones to improve survival of GCs in PHFs from the aged hens. In conclusion, intensified ER stress and apoptosis occurred in GCs of PHFs in aged chickens, while BMP4 secreted by GCs was capable of improving follicular viability by alleviating ER stress to promote follicular development.

Ovarian ageing and the impact on female fertility

Female fertility decreases with increasing age, a reflection of declining oocyte quantity and quality. The menopausal transition occurs when the oocyte quantity falls below a threshold level. The pattern of follicular depletion as well as the factors, timing and mechanisms surrounding both declining oocyte number and oocyte quality remain incompletely understood. Further studies are needed to examine the factors involved and develop predictive models and biomarkers to assist in the management of age-related subfertility. This review summarises the current knowledge addressing the ageing ovary and its impact on fertility.

Trajectories and phenotypes with estrogen exposures across the lifespan: What does Goldilocks have to do with it?

This article is part of a Special Issue "Estradiol and cognition". Estrogens impact the organization and activation of the mammalian brain in both sexes, with sex-specific critical windows. Throughout the female lifespan estrogens activate brain substrates previously organized by estrogens, and estrogens can induce non-transient brain and behavior changes into adulthood. Therefore, from early life through the transition to reproductive senescence and beyond, estrogens are potent modulators of the brain and behavior. Organizational, reorganizational, and activational hormone events likely impact the trajectory of brain profiles during aging. A "brain profile," or quantitative brain measurement for research purposes, is typically a snapshot in time, but in life a brain profile is anything but static--it is in flux, variable, and dynamic. Akin to this, the only thing continuous and consistent about hormone exposures across a female's lifespan is that they are noncontinuous and inconsistent, building and rebuilding on past exposures to create a present brain and behavioral landscape. Thus, hormone variation is especially rich in females, and is likely the destiny for maximal responsiveness in the female brain. The magnitude and direction of estrogenic effects on the brain and its functions depend on a myriad of factors; a "Goldilocks" phenomenon exists for estrogens, whereby if the timing, dose, and regimen for an individual are just right, markedly efficacious effects present. Data indicate that exogenously-administered estrogens can bestow beneficial cognitive effects in some circumstances, especially when initiated in a window of opportunity such as the menopause transition. Could it be that the age-related reduction in efficacy of estrogens reflects the closure of a late-in-life critical window occurring around the menopause transition? Information from classic and contemporary works studying organizational/activational estrogen actions, in combination with acknowledging the tendency for maximal responsiveness to cyclicity, will elucidate ways to extend sensitivity and efficacy into post-menopause.

Age-related decline in ovarian follicle stocks differ between chimpanzees (Pan troglodytes) and humans

Similarity in oldest parturitions in humans and great apes suggests that we maintain ancestral rates of ovarian aging. Consistent with that hypothesis, previous counts of primordial follicles in postmortem ovarian sections from chimpanzees (Pan troglodytes) showed follicle stock decline at the same rate that human stocks decline across the same ages. Here, we correct that finding with a chimpanzee sample more than three times larger than the previous one, which also allows comparison into older ages. Analyses show depletion rates similar until about age 35, but after 35, the human counts continue to fall with age, while the change is much less steep in chimpanzees. This difference implicates likely effects on ovarian dynamics from other physiological systems that are senescing at different rates, and, potentially, different perimenopausal experience for chimpanzees and humans.

A characterization of the relationship of ovarian reserve markers with age

OBJECTIVE

To identify markers of ovarian age that best match the pattern of oocyte loss seen in histology specimens.

DESIGN

Cross-sectional study.

SETTING

University.

PATIENT(S)

Caucasian women (n = 252) aged 25-45 years.

INTERVENTION(S)

none.

MAIN OUTCOME MEASURE(S)

The relationship between antral follicle count (AFC), antimüllerian hormone (AMH), inhibin B, FSH, and E(2) with age was estimated using the power model, which previously has been shown to most accurately describe oocyte loss in histologic specimens. The power model was fit to each marker and used to compare the rates of change at ages 30 and 40 with the histologic pattern. Among those markers following the pattern, R(2) was used to compare the degree of relationship with age.

RESULT(S)

Both AMH levels and AFC exhibited significant progressive declines with age. The average rates of loss per year for AFC and AMH were, respectively, -0.57 and -1.09 at age 30, and -1.33 and -3.06 at age 40. FSH, inhibin B, and E(2) did not exhibit progressive rates of change. The R(2) for AFC was 27.3% and for AMH was 22.7%.

CONCLUSION(S)

Only AFC and AMH follow the pattern of oocyte loss observed histologically. Although AMH may be more cost-effective, AFC is a slightly more accurate noninvasive measure for ovarian aging.

Menopause, A Biocultural Perspective

Each menopausal body is the product of decades of physiological responses to an environment composed of cultural and biological factors. Anthropologists have documented population differences in reproductive endocrinology and developmental trajectories, and ethnic differences in hormones and symptoms at menopause demonstrate that this stage of life history is not exempt from this pattern. Antagonistic pleiotropy, in the form of constraints on the reproductive system, may explain the phenomenon of menopause in humans, optimizing the hormonal environment for reproduction earlier in the life course. Some menopausal symptoms may be side effects of modernizing lifestyle changes, representing discordance between our current lifestyles and genetic heritage. Further exploration of women's experience of menopause, as opposed to researcher-imposed definitions; macro- and microenvironmental factors, including diet and intestinal ecology; and folk etiologies involving the autonomic nervous system may lead to a deeper understanding of the complex biocultural mechanisms of menopause.

Do women stop early? Similarities in fertility decline in humans and chimpanzees

Two kinds of evidence suggest that female fertility may end at an earlier age in modern people than in ancestral populations or in our closest living relatives, chimpanzees. We investigate both to see whether fertility schedules or ovarian follicle counts falsify the alternative hypothesis that the age of terminal fertility changed little in the human lineage while greater longevity evolved due to grandmother effects. We use 19th century Utah women to represent non-contracepting humans, and compare their fertility by age with published records for wild chimpanzees. Then we revisit published counts of ovarian follicular stocks in both species. Results show wide individual variation in age at last birth and oocyte stocks in both humans and chimpanzees. This heterogeneity, combined with interspecific differences in adult mortality, has large and opposing effects on fertility schedules. Neither realized fertility nor rates of follicular atresia stand as evidence against the hypothesis that ages at last birth changed little while greater longevity evolved in our lineage.

Antral follicle count: absence of significant midlife decline

OBJECTIVE

To examine the conventional wisdom that declines in antral follicle count accelerate after approximately 37 years of age, which has influenced clinical decision making. We critically examine evidence for this sudden acceleration.

DESIGN

Cross-sectional study.

SETTING

Academic setting.

PATIENT(S)

Two hundred fifty-two white women aged 25 to 45 years with regular cycles, a community-based study.

INTERVENTION(S)

Antral follicle counts were measured by transvaginal ultrasound in early follicular phase.

MAIN OUTCOME MEASURE(S)

Determination of the rate of antral follicle count decline with age.

RESULT(S)

The relationship of antral follicle count with age was determined by comparing a linear model with four nonlinear models (biphasic, quadratic, spline, and power). The linear model estimates the follicle decline as 0.97 follicles per year. The biphasic model had estimates of 0.76 follicles per year before 39.6 years of age and 1.92 follicles per year thereafter. At age 35 years the linear, quadratic, broken line, spline, and power models gave estimated declines (respectively) of 0.97, 0.94, 0.76, 0.17, and 0.90 follicles per year. At age 43 years the values were 0.97, 1.51, 1.92, 1.78, and 1.64 follicles per year. The quality of model fit was comparable for all models.

CONCLUSION(S)

Antral follicle count decline with age in a white population is best described as a gradual acceleration in decline with age. Therefore antral follicle count alone should not be used to determine aggressive treatment because of fear of rapid loss of follicles.

Ovarian aging: mechanisms and clinical consequences

Menopause is the final step in the process referred to as ovarian ageing. The age related decrease in follicle numbers dictates the onset of cycle irregularity and the final cessation of menses. The parallel decay in oocyte quality contributes to the gradual decline in fertility and the final occurrence of natural sterility. Endocrine changes mainly relate to the decline in the negative feedback from ovarian factors at the hypothalamo-pituitary unit. The declining cohort of antral follicles with age first results in gradually elevated FSH levels, followed by subsequent stages of overt cycle irregularity. The gradual decline in the size of the antral follicle cohort is best represented by decreasing levels of anti-Mullerian hormone. The variability of ovarian ageing among women is evident from the large variation in age at menopause. The identification of women who have severely decreased ovarian reserve for their age is clinically relevant. Ovarian reserve tests have appeared to be fairly accurate in predicting response to ovarian stimulation in the assisted reproductive technology (ART) setting. The capacity to predict the chances for spontaneous pregnancy or pregnancy after ART appears very limited. As menopause and the preceding decline in oocyte quality seem to have a fixed time interval, tests that predict the age at menopause may be useful to assess individual reproductive lifespan. Especially genetic studies, both addressing candidate gene and genome wide association, have identified several interesting loci of small genetic variation that may determine fetal follicle pool development and subsequent wastage of his pool over time. Improved knowledge of the ovarian ageing mechanisms may ultimately provide tools for prediction of menopause and manipulation of the early steps of folliculogenesis for the purpose of contraception and fertility lifespan extension.

Testing ovarian reserve to predict age at menopause

In modern society with women delaying pregnancy, predicting the age of the natural menopause with its preceding infertility will allow making informed choices about when to try starting to have children. Also if premature menopause could be predicted in young women, strategies could be instigated to reduce the long term health risks of early estrogen deficiency. This review examines the physiology of ovarian ageing, with the menopause being the final outcome. Long and short term predictive markers of the age of the menopause and the preceding natural infertility are evaluated. Many subtle changes in the endocrine regulation of ovarian function with advancing age may seem interesting but currently are not clinically useful as a predictive test. Examples are changes in concentrations of estradiol, progesterone, luteinizing hormone (LH) and activin, as well as follicle dynamics. Other features hold more promise. Among these are chronological age, family history, anti-Müllerian hormone (AMH), poor response to in vitro fertilization (IVF), basal follicle-stimulating hormone (FSH) and the antral follicle count for long term prediction. For short term prediction, cycle shortening and occurrence of vasomotor symptoms may prove useful. To date, none of these markers has been found to have sufficient predictive accuracy in individual women. Results of new and ongoing longitudinal studies may provide better predictive models. In particular, use of genetic profiles may add to the accuracy of currently known markers.

Menopause and the human hypothalamus: evidence for the role of kisspeptin/neurokinin B neurons in the regulation of estrogen negative feedback

Menopause is characterized by depletion of ovarian follicles, a reduction of ovarian hormones to castrate levels and elevated levels of serum gonadotropins. Rather than degenerating, the reproductive neuroendocrine axis in postmenopausal women is intact and responds robustly to the removal of ovarian hormones. Studies in both human and non-human primates provide evidence that the gonadotropin hypersecretion in postmenopausal women is secondary to increased gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus. In addition, menopause is accompanied by hypertrophy of neurons in the infundibular (arcuate) nucleus expressing KiSS-1, neurokinin B (NKB), substance P, dynorphin and estrogen receptor alpha (ERalpha) mRNA. Ovariectomy in experimental animals induces nearly identical findings, providing evidence that these changes are a compensatory response to ovarian failure. The anatomical site of the hypertrophied neurons, as well as the extensive data implicating kisspeptin, NKB and dynorphin in the regulation of GnRH secretion, provide compelling evidence that these neurons are part of the neural network responsible for the increased levels of serum gonadotropins in postmenopausal women. We propose that neurons expressing KiSS-1, NKB, substance P, dynorphin and ERalpha mRNA in the infundibular nucleus play an important role in sex-steroid feedback on gonadotropin secretion in the human.

Potential use of biomarkers for analyzing interpopulation and cross-cultural variability in reproductive aging

OBJECTIVE

The aims of this study were (1) to document the extent of variability in physiological aspects of reproductive aging; (2) to outline those areas where more work is needed to expand our knowledge of this variability; (3) to outline available biomarkers that can be used to measure aspects of reproductive aging, such as ovarian reserve and declining hormone levels; and (4) to note potential problems with the use of these biomarkers in cross-cultural settings.

DESIGN

Literature review of English and French publications using PubMed with no date restrictions.

RESULTS

Substantial variability exists in both cultural and physiological aspects of reproductive aging and menopause. However, the extent of variability across populations for many areas of reproductive aging needs better documentation as well as explanation of sources of this variability. Several biomarkers exist for use in cross-cultural research, including ovarian characteristics such as ovarian volume, ovarian reserve, follicular development, and atresia, and levels of hormones such as follicle-stimulating hormone, inhibin B, and anti-mullerian hormone.

CONCLUSION

We urge that further work be undertaken to evaluate and describe variability in physiological aspects of reproductive aging in cross-cultural settings. Some problems exist in the use of biomarkers to record this variability, particularly in remote settings with few logistical resources.

Depletion of ovarian follicles with age in chimpanzees: similarities to humans

We retrieved ovarian sections taken from necropsies of 19 captive chimpanzees (Pan troglodytes) aged 0-47 yr, counted the number of primordial follicles in each, and compared the rate of decline in numbers to declines previously documented in humans. The follicular depletion rate in this sample was indistinguishable from that shown across the same ages in classic human data sets. This result supports earlier suggestions that ovarian senescence occurs at the same ages in chimpanzees and humans, implying that the influence of declining ovarian function on other physiologic systems may be distinctively buffered in humans.

Ovarian aging and menopause: current theories, hypotheses, and research models

Aging of the reproductive system has been studied in numerous vertebrate species. Although there are wide variations in reproductive strategies and hormone cycle components, many of the fundamental changes that occur during aging are similar. Evolutionary hypotheses attempt to explain why menopause occurs, whereas cellular hypotheses attempt to explain how it occurs. It is commonly believed that a disruption in the hypothalamic-pituitary-gonadal axis is responsible for the onset of menopause. Data exist to demonstrate that the first signs of menopause occur at the level of the brain or the ovary. Thus, finding an appropriate and representative animal model is especially important for the advancement of menopause research. In primates, there is a gradual decline in the function of the hypothalamic-pituitary-gonadal (HPG) axis ultimately resulting in irregularities in menstrual cycles and increasingly sporadic incidence of ovulation. Rodents also exhibit a progressive deterioration in HPG axis function; however, they also experience a period of constant estrus accompanied by intermittent ovulations, reduced progesterone levels, and elevated circulating estradiol levels. It is remarkable to observe that females of other classes also demonstrate deterioration in HPG axis function and ovarian failure. Comparisons of aging in various taxa provide insight into fundamental biological mechanisms of aging that could underlie reproductive decline.

On the number of founding germ cells in humans

Background

The number of founding germ cells (FGCs) in mammals is of fundamental significance to the fidelity of gene transmission between generations, but estimates from various methods vary widely. In this paper we obtain a new estimate for the value in humans by using a mathematical model of germ cell development that depends on available oocyte counts for adult women.

Results

The germline-development model derives from the assumption that oogonial proliferation in the embryonic stage starts with a founding cells at t = 0 and that the subsequent proliferation can be defined as a simple stochastic birth process. It follows that the population size X(t) at the end of germline expansion (around the 5^th month of pregnancy in humans; t = 0.42 years) is a random variable with a negative binomial distribution. A formula based on the expectation and variance of this random variable yields a moment-based estimate of a that is insensitive to the progressive reduction in oocyte numbers due to their utilization and apoptosis at later stages of life. In addition, we describe an algorithm for computing the maximum likelihood estimation of the FGC population size (a), as well as the rates of oogonial division and loss to apoptosis. Utilizing both of these approaches to evaluate available oocyte-counting data, we have obtained an estimate of a = 2 – 3 for Homo sapiens.

Conclusion

The estimated number of founding germ cells in humans corresponds well with values previously derived from chimerical or mosaic mouse data. These findings suggest that the large variation in oocyte numbers between individual women is consistent with a smaller founding germ cell population size than has been estimated by cytological analyses.

Predictors of antral follicle count during the reproductive years

BACKGROUND

We sought to identify indicators of antral follicle count which would be serviceable to clinicians seeking to estimate the number of ovarian follicles without relying on sonographic counts.

METHODS

We examined the relations of chronological age and four potential indicators of ovarian age-ovarian volume, FSH, dimeric inhibin B and estradiol-to antral follicle count in 176 recently pregnant women. We identified the regression models which best predict low antral follicle count (< or =10 follicles).

RESULTS

Chronological age, ovarian volume, FSH and inhibin B were each significantly associated with antral follicle count. Fifty-three (30.1%) women had < or =10 antral follicles. In the total sample, at the cutpoint corresponding to 80% sensitivity, the positive predictive value for a regression model with all four variables was 60%. All regression models performed less well in women <35 years (13.9% with low count) than in women > or =35 years (52.0% with low count). In older women, the positive predictive value for the model with all four variables was 79%, compared with 60% for a model with chronological age alone.

CONCLUSIONS

Our models provide a basis for advising women aged > or =35 years who are either trying to conceive or wish to learn whether they may postpone childbearing.

Antral follicle counts are related to age at natural fertility loss and age at menopause

OBJECTIVE

The variability in ultrasound-based antral follicle counts sized 2-10 mm after allowing for age-related decline is considerable. This may represent differences in actual reproductive age among women. This hypothesis was tested by cohort comparison for distribution of age at occurrence of reproductive events.

DESIGN

A model with a nonlinear mean decline with age was fitted to antral follicle counts (AFC) obtained in 163 regularly cycling fertile volunteers. Ages at last child birth and menopause were predicted from the individual AFC by using thresholds to represent these events and the model for decline with age. Distributions of the observed ages at last childbirth (proxy variable for loss of natural fertility) and ages at menopause were obtained from the BALSAC demographic database and the Prospect-EPIC study, respectively. The observed distributions were compared with the predicted distributions by using visual comparison and quantile-quantile plots. Predictions of age at last child and age at menopause were done using percentiles of the modeled AFC distribution for given age, and corresponding percentiles of the predicted distributions of age at these reproductive events, with predictions following from the position of a woman's AFC relative to these percentiles.

RESULTS

The predicted distributions of age at last child and age at menopause showed good agreement with the observed distributions in the BALSAC and EPIC cohort. Compared with age alone, antral follicle counts gave some additional information for individual prediction of age at last child and menopause.

CONCLUSIONS

The link between declining antral follicle counts and reproductively significant events like loss of natural fertility and menopause is strengthened by the high degree of similarity among the predicted and observed age distributions. Predictive usefulness of this relationship in a clinical setting may be more marginal, except in the case of women who have low AFCs for their age.

Assessment of reproductive ageing patterns by hormonal and ultrasonographic ovarian reserve tests

BACKGROUND

Tests to assess the change in ovarian reserve (OR) with age have been analysed only in monophasic or biphasic linear patterns. Our aim was to analyse an optimum curve that might define the relationship between different OR tests and age.

METHODS

A total of 81 regularly menstruating women without a history of infertility were included in this prospective study. On cycle day 3, antral follicle (AF) counts, ovarian volume (OV), and serum FSH and estradiol levels were determined. Curve estimation was performed to determine the optimal relationship between age and OR tests. Optimum curves were also compared with monophasic and biphasic linear relationships.

RESULTS

A quadratic model (y=a x x2+b x x+c) had the highest coefficient of determination for the AF count, OV and serum FSH level. The predictive power of this quadratic model was comparable with biphasic linear models for the OV and serum FSH level, but was better than that of the AF count.

CONCLUSIONS

The pattern of reproductive ageing as assessed by hormonal and ultrasonographic OR tests does not appear to show an abrupt change at a certain age, but follows a continuously increasing rate of decline in the third decade of life. The changes in serum FSH levels and ultrasonographic OR tests follow a quadratic model in regularly menstruating women.

Reproductive hormones: ageing and the perimenopause

This review explores the pituitary-ovarian hormones involved with ageing and the onset of menopause. The serum patterns of pituitary-ovarian hormones throughout the menstrual cycle alter as menopause approaches. The increase in follicular phase FSH prior to menopause is attributed to an early decline in the ovarian hormone, inhibin B, which negatively regulates follicle-stimulating hormone (FSH) secretion. Serum inhibin B is believed to reflect the age-related decrease in ovarian follicle reserve, which is the primary source of serum inhibin B. The later rise in serum luteinizing hormone (LH) during the menopause transition is due to a cessation of ovarian follicle development. Hormonal patterns during the luteal phase of the menstrual cycle also show changes with age but these changes are poorly understood.

Influence of patient age on the growth and transfer of blastocyst-stage embryos

OBJECTIVE

To examine the effects of patient age on the growth and transfer of blastocyst-stage embryos.

DESIGN

Retrospective clinical study.

SETTING

Private assisted reproductive technologies center.

PATIENT(S)

Three hundred patients between the ages of 18 and 45 undergoing in vitro fertilization.

INTERVENTION(S)

Bipronucleate oocytes were grown for up to 144 hours and subsequently transferred when at least one embryo attained the expanded blastocyst stage.

MAIN OUTCOME MEASURE(S)

Oocytes retrieved and fertilized, blastocyst formation rates, implantation rates, and pregnancy rates per retrieval and transfer.

RESULT(S)

The rate of cycle cancellation before oocyte retrieval increased significantly with age, and the average number of oocytes per retrieval declined significantly with age. Fertilization rates were unrelated to patient age. The proportion of cycles with expanded blastocysts declined significantly with age. Pregnancy rates per stimulation declined with age, but pregnancy rates per transfer were approximately 50% across the entire age range studied.

CONCLUSION(S)

The decline in female fertility with age appears to be the result of reduced numbers of oocytes and the inability of fertilized oocytes to develop to the blastocyst stage. Implantation and pregnancy rates appear to be unaffected by age when blastocysts do form.

A critique of the grandmother hypotheses: old and new

The singularity of reproductive senescence in human females has led many investigators to consider menopause an adaptation permitting increased maternal investment in existing progeny. Much of the focus has been on the grandmother hypothesis-the notion that aging women gain an inclusive fitness advantage from investing in their grandchildren. This hypothesis has evolved from an explanation for menopause into an explanation for the exceptionally long postreproductive lifespan in human females. In the old grandmother hypothesis, menopause is an adaptation facilitating grandmothering; it is about stopping early in order to create a postreproductive lifespan. In the new grandmother hypothesis, grandmothering is an adaptation facilitating increased longevity, and menopause is a byproduct. This paper reviews and critically evaluates the evidence for and against both hypotheses, focusing on key predictions of each. If menopause is the result of selection for increased maternal investment, this involved mainly mothers, not grandmothers.

Menstrual cycle variability and the perimenopause

Menopause, the final cessation of menstrual cycling, occurs when the pool of ovarian follicles is depleted. The one to five years just prior to the menopause are usually marked by increasing variability in menstrual cycle length, frequency of ovulation, and levels of reproductive hormones. Little is known about the mechanisms that account for these characteristics of ovarian cycles as the menopause approaches. Some evidence suggests that the dwindling pool of follicles itself is responsible for cycle characteristics during the perimenopausal transition. Another hypothesis is that the increased variability reflects "slippage" of the hypothalamus, which loses the ability to regulate menstrual cycles at older reproductive ages. This paper examines the underlying cause of the increasing variability in menstrual cycle length prior to the menopause. A model of ovarian cycles is developed, based on the process of follicular growth and depletion. Under this model, the follicular phase of each menstrual cycle is preceded by an inactive phase, a period of time when no ovarian follicles have left the resting state and begun secreting steroids in response to gonadotropin stimulation. The model makes predictions about the variability in menstrual cycles across the reproductive life span based on the size of the surviving pool of ovarian follicles. We show that the model can explain several characteristics of the perimenopause in humans and macaques and illustrate how the model can be applied to research on the biological and cultural correlates of the timing of menopause.

Antral follicle counts by transvaginal ultrasonography are related to age in women with proven natural fertility

OBJECTIVE

To investigate the relation between reproductive age and ultrasound (US)-based follicle counts and the reproducibility of follicle counts in regularly cycling women with proven fertility.

DESIGN

Prospective observational study.

SETTING

Tertiary fertility center.

PATIENT(S)

Healthy female volunteers with proven fertility, recruited by advertisement in local newspapers.

INTERVENTION(S)

The number of antral follicles sized 2-10 mm and ovarian volume were estimated by transvaginal US in the early follicular phase of the menstrual cycle in 162 women. A subgroup of 81 women underwent transvaginal US at several times in three subsequent cycles.

MAIN OUTCOME MEASURE(S)

Antral follicle count and total ovarian volume.

RESULT(S)

Women aged 25-46 years (n = 162) were studied. The relation of age with the US indices was computed after natural log transformation. Antral follicle count showed the clearest correlation with age (R = -0.67). A biphasic linear model gave the best fit to the data. Before the age of 37 years, the antral follicle count showed a mean yearly decline of 4.8%, compared with 11.7% thereafter. The reproducibility of the antral follicle count in two subsequent cycles was moderate.

CONCLUSION(S)

The number of small antral follicles in both ovaries as measured by US is clearly related to reproductive age and could well reflect the size of the remaining primordial follicle pool.