Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome

Since the 1990 National Institutes of Health-sponsored conference on polycystic ovary syndrome (PCOS), it has become appreciated that the syndrome encompasses a broader spectrum of signs and symptoms of ovarian dysfunction than those defined by the original diagnostic criteria. The 2003 Rotterdam consensus workshop concluded that PCOS is a syndrome of ovarian dysfunction along with the cardinal features hyperandrogenism and polycystic ovary (PCO) morphology. PCOS remains a syndrome, and as such no single diagnostic criterion (such as hyperandrogenism or PCO) is sufficient for clinical diagnosis. Its clinical manifestations may include menstrual irregularities, signs of androgen excess, and obesity. Insulin resistance and elevated serum LH levels are also common features in PCOS. PCOS is associated with an increased risk of type 2 diabetes and cardiovascular events.

EGF-Like Growth Factors As Mediators of LH Action in the Ovulatory Follicle

Before ovulation in mammals, a cascade of events resembling an inflammatory and/or tissue remodeling process is triggered by luteinizing hormone (LH) in the ovarian follicle. Many LH effects, however, are thought to be indirect because of the restricted expression of its receptor. Here, we demonstrate that LH stimulation induces the transient and sequential expression of the epidermal growth factor (EGF) family members amphiregulin, epiregulin, and beta-cellulin. Incubation of follicles with these growth factors recapitulates the morphological and biochemical events triggered by LH, including cumulus expansion and oocyte maturation. Thus, these EGF-related growth factors are paracrine mediators that propagate the LH signal throughout the follicle.

Obesity and the polycystic ovary syndrome

The polycystic ovary syndrome (PCOS) is a condition characterized by hyperandrogenism and chronic oligo-anovulation. However, many features of the metabolic syndrome are inconsistently present in the majority of women with PCOS. Approximately 50% of PCOS women are overweight or obese and most of them have the abdominal phenotype. Obesity may play a pathogenetic role in the development of the syndrome in susceptible individuals. In fact, insulin possesses true gonadotrophic function and an increased insulin availability at the level of ovarian tissue may favour excess androgen synthesis. Obesity, particularly the abdominal phenotype, may be partly responsible for insulin resistance and associated hyperinsulinemia in women with PCOS. Therefore, obesity-related hyperinsulinemia may play a key role in favouring hyperandrogenism in these women. Other factors such as increased estrogen production rate, increased activity of the opioid system and of the hypothalamic-pituitary-adrenal axis, decreased sex hormone binding globulin synthesis and, possibly, high dietary lipid intake, may be additional mechanisms by which obesity favours the development of hyperandrogenism in PCOS. Irrespective of the pathogenetic mechanism involved, obese PCOS women have more severe hyperandrogenism and related clinical features (such as hirsutism, menstrual abnormalities and anovulation) than normal-weight PCOS women. This picture tends to be more pronounced in obese PCOS women with the abdominal phenotype. Body weight loss is associated with beneficial effects on hormones, metabolism and clinical features. A further clinical and endocrinological improvement can also be achieved by adding insulin-sensitizing agents and/or antiandrogens to weight reduction programmes. These obviously emphasize the role of obesity in the pathophysiology of PCOS.

Episodic luteinizing hormone secretion in man. Pulse analysis, clinical interpretation, physiologic mechanisms

The demonstration that luteinizing hormone (LH) release from the pituitary is episodic rather than constant raises fundamental questions regarding the physiologic control of pulsatile LH secretion and its possible alteration in patients with gonadal disorders. To evaluate this mode of LH secretion, quantitative means of analyzing LH pulse amplitude, frequency, shape, and area were established and utilized to study normal subjects and patients with disorders of gonadotropin secretion. Similar patterns of LH secretion were observed in normal men, in women during the follicular phase of the menstrual cycle, and in patients with hyper- and hypogonadotropism, hirsuitism, and amenorrhea (mean pulse amplitude 39-179% from nadir to peak, frequency 2.7-3.9 secretory spikes/6 h). These observations suggested that the pattern of LH secretion is similar in both normal individuals and in those with a variety of pathologic conditions. By contrast, the pattern of pulsatile secretion appeared to differ in the following conditions. LH pulses of higher amplitude (333+/-170%) and lower frequency (1.6+/-0.24 SEM/6 h) characterized the secretory patterns of women during the luteal phase of the menstrual cycle, suggesting that gonadal steroids may modulate LH pulses. LH pulses of low amplitude (26+/-2.1%) and frequency (1.3+/-0.36/6 h) were observed in women with anorexia nervosa. Either integrated LH levels or a mean LH level determined from multiple samples provided a more accurate reflection of gonadotropin secretion than the use of single LH measurements. With multiple sampling over 6 h, it was possible to reduce the 95% confidence limit of LH estimates from +/-50-90 to +/-12%. This allowed normal subjects to be distinguished from patients with low or moderately elevated LH levels in whom gonadotropin levels in single samples were often in the "normal range."Several aspects of the physiologic control of pulsatile LH secretion were studied. The concordance of follicle-stimulating hormone (FSH) with LH pulses progressively increased as LH pulse height increased (P < 0.01) suggesting possible hypothalamic mediation of gonadotropin pulses. Measurement of the "apparent half-life" of LH after secretory spikes revealed half times of 34-233 min. It is likely that this variability was attributable to at least two phenomena: (a) constant low level LH secretion that continued after certain secretory episodes but not others; (b) variable mixing of newly secreted LH into at least two pools. The alpha adrenergic-blocking agents, chlorpromazine and phentolamine, failed to block LH secretory spikes at doses sufficient to result in a 30 mm drop in systolic blood pressure in normal men.

Progesterone-regulated genes in the ovulation process: ADAMTS-1 and cathepsin L proteases

Ovulation is a precisely timed process by which a mature oocyte is released from an ovarian follicle. This process is initiated by the pituitary surge of luteinizing hormone (LH), is temporally associated with transcriptional regulation of numerous genes, and is presumed to involve the synthesis and/or activation of specific proteases that degrade the follicle wall. The progesterone receptor (PR), a nuclear receptor transcription factor, is induced in granulosa cells of preovulatory follicles in response to the LH surge and has been shown to be essential for ovulation, because mice lacking PR fail to ovulate and are infertile. Using these mice as a model in which to elucidate PR-regulated genes in the ovulation process, we show that the matrix metalloproteinases MMP-2 and MMP-9 are not targets of PR during ovulation. In contrast, two other proteases, ADAMTS-1 (A disintegrin and metalloproteinase with thrombospondin-like motifs) and cathepsin L (a lysosomal cysteine protease), are transcriptional targets of PR action. ADAMTS-1 is induced after LH stimulation in granulosa cells of preovulatory follicles and depends on PR. Cathepsin L is induced in granulosa cells of growing follicles by follicle-stimulating hormone, but the highest levels of cathepsin L mRNA occur in preovulatory follicles in response to LH in a PR-dependent manner. The identification of two regulated proteases in the ovary, together with their abnormal expression in anovulatory PR knockout mice, suggests that each plays a critical role in follicular rupture and represents a major advance in our understanding of the proteolytic events that control ovulation.

The EGR family of transcription-regulatory factors: progress at the interface of molecular and systems neuroscience

The EGR family of transcription regulatory factors, which is implicated in orchestrating the changes in gene expression that underlie neuronal plasticity, has attracted the attention of both molecular and systems neuroscientists. In this article, the advances made in both these fields of research are reviewed. Recent systems-based studies underscore the remarkable sensitivity and specificity of the induction of the expression of genes encoding EGR-family members in naturally occurring plasticity paradigms. However, they also challenge conventional views of the role of this family in plasticity. Recent molecular studies have identified the gonadotropin subunit, luteinizing hormone beta, as an EGR1-regulated gene in vivo and uncovered an essential role for EGR3 in muscle-spindle development. In addition, the discovery of novel proteins that are capable of suppressing EGR-mediated transcription cast doubt over the prevalent assumption that changes in EGR mRNA or protein levels provide an accurate measure of EGR-driven transcriptional activity.

The science behind 25 years of ovarian stimulation for in vitro fertilization

To allow selection of embryos for transfer after in vitro fertilization, ovarian stimulation is usually carried out with exogenous gonadotropins. To compensate for changes induced by stimulation, GnRH analog cotreatment, oral contraceptive pretreatment, late follicular phase human chorionic gonadotropin, and luteal phase progesterone supplementation are usually added. These approaches render ovarian stimulation complex and costly. The stimulation of multiple follicular development disrupts the physiology of follicular development, with consequences for the oocyte, embryo, and endometrium. In recent years, recombinant gonadotropin preparations have become available, and novel stimulation protocols with less detrimental effects have been developed. In this article, the scientific background to current approaches to ovarian stimulation for in vitro fertilization is reviewed. After a brief discussion of the relevant aspect of ovarian physiology, the development, application, and consequences of ovarian stimulation strategies are reviewed in detail.

Cyclic GMP from the surrounding somatic cells regulates cyclic AMP and meiosis in the mouse oocyte

Mammalian oocytes are arrested in meiotic prophase by an inhibitory signal from the surrounding somatic cells in the ovarian follicle. In response to luteinizing hormone (LH), which binds to receptors on the somatic cells, the oocyte proceeds to second metaphase, where it can be fertilized. Here we investigate how the somatic cells regulate the prophase-to-metaphase transition in the oocyte, and show that the inhibitory signal from the somatic cells is cGMP. Using FRET-based cyclic nucleotide sensors in follicle-enclosed mouse oocytes, we find that cGMP passes through gap junctions into the oocyte, where it inhibits the hydrolysis of cAMP by the phosphodiesterase PDE3A. This inhibition maintains a high concentration of cAMP and thus blocks meiotic progression. LH reverses the inhibitory signal by lowering cGMP levels in the somatic cells (from approximately 2 microM to approximately 80 nM at 1 hour after LH stimulation) and by closing gap junctions between the somatic cells. The resulting decrease in oocyte cGMP (from approximately 1 microM to approximately 40 nM) relieves the inhibition of PDE3A, increasing its activity by approximately 5-fold. This causes a decrease in oocyte cAMP (from approximately 700 nM to approximately 140 nM), leading to the resumption of meiosis.

Follicular oestrogen synthesis: the 'two-cell, two-gonadotrophin' model revisited

The original 'two-cell mechanism' explained the endocrine regulation of follicular oestrogen synthesis and implied paracrine signalling in the follicle wall. It is now known that the CYP17 gene encoding 17-hydroxylase/C17-20-lyase activity crucial to androgen synthesis, is expressed exclusively in thecal cells. 17-Hydroxylase/C17-20-lyase activity is regulated by LH and subject to local modulation by a factor(s) emanating in FSH-stimulated granulosa cells. The FSH receptor gene is expressed exclusively in granulosa cells, where FSH acts directly to induce cytoproliferation and differentiation via cyclic AMP/protein kinase-A mediated post-receptor signalling. Granulosa cells also express androgen receptors, and theca-derived androgen has the potential to modulate locally differentiative responses to FSH. When follicles are recruited to preovulatory development by FSH, their granulosa cells develop LH receptors functionally coupled to aromatase activity and inhibin production. Thereby they simultaneously undertake LH-responsive aromatization and inhibin synthesis. Inhibin has the potential to potently enhance LH-stimulated thecal androgen synthesis. Granulosa-derived inhibin may therefore participate in a paracrine mechanism that locally amplifies androgen synthesis, and hence oestrogen formation, in the preovulatory follicle(s).

Role of the epidermal growth factor network in ovarian follicles

The LH surge causes major remodeling of the ovarian follicle in preparation for the ovulatory process. These changes include reprogramming of granulosa cells to differentiate into luteal cells, changes in cumulus cell secretory properties, and oocyte maturation. This review summarizes published data in support of the concept that LH stimulation of ovarian follicles involves activation of a local epidermal growth factor (EGF) network. A model describing this property of LH signaling and its branching to other signaling modules is discussed. According to this model, LH activation of mural granulosa cells stimulates cAMP signaling, which, in turn, induces the expression of the EGF-like growth factors epiregulin, amphiregulin, and betacellulin. These growth factors function by activating EGF receptors in either an autocrine/juxtacrine fashion within the mural layer, or they diffuse to act on cumulus cells. Activation of EGF receptor signaling in cumulus cells, together with cAMP priming, triggers oocyte nuclear maturation and acquisition of developmental competence as well as cumulus expansion. This model has important implications for ovarian physiology and for the development of new strategies for the pharmacological control of ovulation and for gamete maturation in vitro.

Novel signaling mechanisms in the ovary during oocyte maturation and ovulation

During the peri-ovulatory period, the gonadotropin LH triggers major changes in both the somatic and germ cell compartments of the ovarian follicle. The oocyte completes the meiotic cell cycle to become a fertilizable egg, and dramatic changes in gene expression and secretion take place in the somatic compartment of the follicle in preparation for follicular rupture and oocyte release. The concerted changes are regulated by activation of intracellular signaling pathways as well as paracrine and autocrine regulatory loops. This review will provide a summary of the current knowledge of the molecular events triggered by LH focusing mostly on the signaling pathways required for oocyte maturation.

Hypothalamic regulatory hormones

The molecular structures of several polypeptides isolated from hypothalamic tissue have been established and the synthesis of these compounds has been achieved. These polypeptides selectively stimulate or inhibit the release of anterior pituitary hormones and melanocyte-stimulating hormone. Various studies indicate their important physiological role and support the concept that some of these polypeptides are hormones. Some synthetic hypothalamic hormones and their derivatives may find important clinical and veterinary applications.

Gonadotropic control of ovarian follicular growth and development

Development-related paracrine cues that sensitize follicles to follicle stimulating hormone (FSH) and luteinizing hormone (LH) are crucial to the emergence of a single dominant follicle in each ovulatory menstrual cycle. Sex steroids, insulin-like growth factors and members of the transforming growth factor-beta superfamily are key players in the follicular paracrine system. FSH acts through membrane-associated granulosa cell receptors (FSHR) to stimulate granulosa cell proliferation and differentiation. The most responsive follicle at the beginning of the cycle is the first to produce estrogen and express granulosa cell LHR. Paracrine signalling activated by FSH and LH sustains growth and oestrogen secretion until an ovulation-inducing LH surge is discharged by the pituitary gland. LH then reprograms granulosa cell function, leading to terminal differentiation (luteinization) rupture of the follicle wall, and release of the fertilizable egg. The genes regulated by the LH surge orchestrate profound changes in sex steroid production, metabolism and action which are necessary for ovulation. Preovulatory granulosa cells also increase their ability to metabolise cortisone to cortisol, which may be part of a local anti-inflammatory mechanism to promote rapid healing of the ruptured ovarian surface.

Current concepts of the roles of follicle stimulating hormone and luteinizing hormone in folliculogenesis

Around 400 follicles sequentially mature and ovulate during an average woman's reproductive lifetime. From birth to the menopause, the other approximately 99.98% of her follicles begin development but never complete it. Instead they default to atresia due to inadequate stimulation by follicle stimulating hormone (FSH). Follicular growth to the stage of antrum formation (approximately 0.25 mm diameter) is independent of gonadotrophic stimulation. Antrum formation and further growth to the stage at which follicles become potentially able to begin preovulatory development (2-5 mm diameter) require tonic stimulation by FSH. Before onset of puberty, blood concentrations of FSH do not rise sufficiently to sustain development beyond this stage, therefore all antral follicles become atretic. After puberty, as each menstrual cycle begins, FSH concentrations rise beyond a critical 'threshold' and multiple follicles are recruited to begin pre-ovulatory development. Due to increases in its responsiveness to FSH and luteinizing hormone (LH), one of these follicles becomes selected to ovulate while the remainder become atretic. At mid-follicular phase, the dominant follicle reaches > or = 10 mm in diameter and increasingly synthesizes oestradiol. Tonic stimulation by FSH and LH, underpinned by local paracrine signalling, maintains oestrogen secretion by the dominant follicle, which grows to > or = 20 mm in diameter before it ovulates in response to the mid-cycle LH surge. The development-related response to LH shown by the pre-ovulatory follicle raises the possibility that exogenous LH might be used as an adjunct to therapy with exogenous FSH in clinical ovulation induction regimens where the aim is to induce monovulation.

Paracrine regulation of mammalian oocyte maturation and male germ cell survival

Mammalian oocytes are arrested at the prophase of meiosis before induction of maturation by the preovulatory luteinizing hormone (LH) surge. LH also promotes the survival of meiotic male germ cells in the testis. Because LH binds somatic cells, the mechanism underlying its regulation of germ cell function is unclear. We found that LH stimulates Leydig insulin-like 3 (INSL3) transcripts in ovarian theca and testicular Leydig cells. INSL3, in turn, binds a G protein-coupled receptor, LGR8 (leucine-rich repeat-containing G protein-coupled receptor 8), expressed in germ cells to activate the inhibitory G protein, thus leading to decreases in cAMP production. Treatment with INSL3 initiates meiotic progression of arrested oocytes in preovulatory follicles in vitro and in vivo and suppresses male germ cell apoptosis in vivo, thus demonstrating the importance of the INSL3-LGR8 paracrine system in mediating gonadotropin actions.

Epidermal growth factor family members: endogenous mediators of the ovulatory response

Previous studies showed that epidermal growth factor (EGF) and TGFalpha mimic the action of LH on the resumption of oocyte maturation. We tested whether EGF-like agents, such as amphiregulin (AR), epiregulin (ER), and betacellulin (BTC), also mediate the LH stimulation of the ovulatory response in the rat. LH induced transient follicular expression of AR, ER, and BTC mRNA, reaching a maximum after 3-h incubation. Furthermore, the addition of ER, AR, and BTC to the culture medium could mimic some of LH actions. AR and ER fully simulated LH-induced resumption of meiosis in vitro, whereas BTC was less effective. To study the putative involvement of EGF-like factors in mediation of LH signal, the effect of the EGF receptor kinase inhibitor AG1478 was tested. When added with LH, AG1478, but not its inactive analog AG43, reduced EGF receptor phosphorylation and oocyte maturation compared with follicles treated with LH only. In addition to the inhibition of resumption of meiosis, AG1478 administration into the bursa (3 microg/bursa) resulted in 51% (P < 0.0005) inhibition of ovulation in the treated ovaries, compared with the untreated contralateral ones, as well as to the vehicle-treated ovaries (P < 0.02). LH, as well as ER, induced the expression of genes associated with the ovulatory response like rat hyaluronan synthase-2, cyclooxygenase-2, and TNFalpha-stimulated gene 6 mRNA, whereas AG1478 inhibited this effect of LH. Release of EGF-like factors from the membrane is dependent on activated metalloproteases. Indeed, Galardin, a broad-spectrum metalloprotease inhibitor, but not a specific matrix metalloprotease 2 and 9 inhibitor, suppressed meiotic maturation induced by LH. Conversely, meiotic maturation induced by ER was not affected by Galardin, thus, supporting the notion that LH releases follicular membrane-bound EGF-like agents. In summary, EGF-like factors such as ER, AR, and BTC seem to mediate, at least partially, the LH stimulation of oocyte maturation, ovulatory enzyme expression, and ovulation.

Follicle selection in monovular species

Follicle deviation is proposed to be the eminent event in follicle selection in monovular species. At deviation, the largest follicle establishes dominance apparently before the second-largest follicle can reach a similar diameter. In cattle, based on diameters of the two follicles at the beginning of deviation, the mechanism becomes established in <8 h. An FSH:follicle-coupling hypothesis has been supported as the essence of follicle selection. According to the hypothesis, the growing follicles cause the FSH decline from the peak of the wave-stimulating FSH surge until deviation, even though the follicles continue to require FSH (two-way functional coupling involving multiple follicles). During multiple-follicle coupling, inhibin is the primary FSH suppressant. Near the beginning of deviation, the largest follicle secretes increased estradiol, and apparently both estradiol and inhibin contribute to the continuing FSH decline; only the more-developed largest follicle is able to utilize the low FSH concentrations (single-follicle coupling). Deviation is encompassed by a transient elevation in LH in heifers and by a component, often distinct, of the long ovulatory LH surge in mares. In heifers, receptors for LH appear in the granulosa cells of the future dominant follicle about 8 h before the beginning of deviation. The LH stimulates the production of estradiol and insulin-like growth factor-1. These intrafollicular factors and perhaps others account for the responsiveness of the largest follicle to the low concentrations of FSH. The smaller follicles have not reached a similar developmental stage and because of their continued and close dependency on FSH become susceptible to the low concentrations. Thereby, follicle selection is established.

The presence of gonadotropin receptors in nonpregnant human uterus, human placenta, fetal membranes, and decidua

The possible presence of gonadotropin receptors in nonpregnant human uterus and human fetoplacental unit was investigated by light microscope immunocytochemistry using a monoclonal antibody to rat luteal hCG/LH receptors. The receptor antibody cross-reacted with human and bovine hCG/LH receptors and appears to be directed against the receptor rather than other proteins, including HLA class I antigens. Uterus and fetoplacental unit contained receptor antibody-binding sites, which indicates the presence of hCG/LH receptors. In the endometrium these receptors were present in glandular and luminal epithelial cells as well as in stromal cells. In the myometrium the receptors were detected in circular and elongated myometrial smooth muscle and vascular smooth muscle. Comparison of immunostaining intensities, which indicates the presence of different amounts of receptors, revealed that luminal and glandular epithelial cells contained more receptors than stromal cells. These cells, in turn, contained more receptors than myometrial and vascular smooth muscle. All cells in secretory phase uterine specimens contained more receptors than corresponding cells from the proliferative phase of the cycle. Midpregnancy placenta, amniotic epithelium, chorionic cytotrophoblasts, and decidual cells contained hCG/LH receptors. At term pregnancy, while receptors in fetal membranes and decidua continue to be detected, placental tissues did not show any detectable receptors unless the tissues were pretreated with neuraminidase. This indicated that term pregnancy placenta contain hCG/LH receptors masked by sialic acid residues. Comparison of immunostaining intensities suggested that syncytiotrophoblasts contained more receptors than cytotrophoblasts at midpregnancy; mesenchymal cells or blood vessels contained no detectable receptors. There were more receptors in decidua than in fetal membranes at mid- and term pregnancy. While the amniotic epithelial receptors decreased, the receptors in chorionic cytotrophoblasts and decidual cells increased from mid- to term pregnancy. In summary, hCG/LH receptors were demonstrated in the nonpregnant human uterus, human placenta, fetal membranes, and decidua. This indicates that hCG/LH may directly regulate functions of these tissues by endocrine, autocrine, or paracrine mechanisms.

Development of a methodology for and assessment of pulsatile luteinizing hormone secretion in juvenile and adult male mice

Current methodology to monitor pulsatile LH release in mice is limited by inadequate assay sensitivity, resulting in the need for collection of large blood volumes. Thus, assessment of pulsatile LH secretion in mice remains highly challenging, and observations are limited to adult mice. To address this, we developed a highly sensitive ELISA for assessment of mouse LH concentrations in small fractions of whole blood. We demonstrate that this assay is capable of reliably detecting LH down to a theoretical limit of 0.117 ng/mL in a 2-μL fraction of whole blood. Using an established frequent blood collection procedure, we validated the accuracy of this method by determining the pulsatile LH secretion in early-adult (10 weeks old) C57BL6/J male mice. Data demonstrate regular pulsatile release of LH, with peaks in LH secretion rarely exceeding 3 ng/mL. Moreover, assessment of LH release in Gpr54 knockout mice demonstrates the lack of pulsatile LH release after the loss of kisspeptin-mediated pubertal maturation. We next determined age-associated changes in pulsatile LH secretion by assessment of LH secretion in prepubertal (28 days old) C57BL6/J male mice and repeated assessment in the same mice in adulthood (120 days old). Data demonstrate that the rise in total LH secretion in mice after pubertal maturation occurs along with an overall rise in the pulsatile LH secretion rate. This was coupled with a significant increase in the number of LH secretory events (number of pulses). In addition, we observed a decrease in the clearance (increased half-life) and a decrease in the regularity (approximate entropy) of LH release. This method will be of wide general utility within the field of reproductive biology.