Polycystic ovarian syndrome: evidence that flutamide restores sensitivity of the gonadotropin-releasing hormone pulse generator to inhibition by estradiol and progesterone

Polycystic ovarian syndrome (PCOS) is a complex disorder with multiple abnormalities, including hyperandrogenism, ovulatory dysfunction, and altered gonadotropin secretion. The majority of patients have elevated LH levels in plasma and a persistent rapid frequency of LH (GnRH) pulse secretion, the mechanisms of which are unclear. Earlier work has suggested that the sensitivity of the GnRH pulse generator to inhibition by ovarian steroids is impaired. We performed a study to determine whether antiandrogen therapy with flutamide could enhance feedback inhibition by estradiol (E2) and progesterone (P) in women with PCOS. Ten anovulatory women with PCOS and nine normal controls (days 8-10 of the cycle) were studied on three occasions. During each admission, LH and FSH were determined every 10 min and E2, P, and testosterone (T) every 2 h for 13 h. After 12 h, GnRH (25 ng/kg) was given iv. After the first admission, patients were started on flutamide (250 mg twice daily), which was continued for the entire study. The second admission occurred on days 8-10 of the next menstrual cycle for normal controls and on study day 28 for PCOS patients. Subjects were then given E2 transdermally (mean plasma E2, 106+/-18 pg/mL) and P by vaginal suppository to obtain varied plasma concentrations of P (mean P, 4.4+/-0.5 ng/mL; range, 0.6-9.0 ng/mL), and a third study was performed 7 days later. At baseline women with PCOS had higher LH pulse amplitude, response to GnRH, T, androstenedione, and insulin and lower sex hormone-binding globulin concentrations (P < 0.05). Most hormonal parameters were not altered by 4 weeks of flutamide, except T in controls and E2 and FSH in PCOS patients, which were lower. Of note, flutamide alone had no effect on LH pulse frequency or amplitude, mean plasma LH, or LH responsiveness to exogenous GnRH. After the addition of E2 and P for 7 days, both PCOS patients and normal controls had similar reductions in LH pulse frequency (4.0+/-0.7 and 5.8+/-0.7 pulses/12 h, respectively). This contrasts with our earlier results in the absence of flutamide, where a plasma P level of less than 10 ng/mL had minimal effects on LH pulse frequency in women with PCOS, but was effective in controls. These results suggest that although the elevated LH pulse frequency in PCOS may in part reflect impaired sensitivity to E2 and P, continuing actions of hyperandrogenemia are important for sustaining the abnormal hypothalamic sensitivity to feedback inhibition by ovarian steroids.     

Evidence for insulin suppression of baseline luteinizing hormone in women with polycystic ovarian syndrome and normal women

CONTEXT: In women with polycystic ovarian syndrome (PCOS), the relationship of insulin to LH secretion and responses to GnRH remains unresolved. A rigorous analytical examination of this relationship has not been performed. OBJECTIVE: Our objective was to determine the relationship of basal LH secretion and responses to GnRH, insulin, and other endocrine variables in normal and PCOS women. DESIGN: In PCOS and normal women, mean composite 12-h LH secretion was analyzed for correlating factors. LH responses to varying doses of GnRH during a fixed rate of insulin infusion and LH responses to a fixed dose of GnRH during varying doses of insulin infusion were analyzed for contributing factors. PATIENTS AND SETTING: Eighteen PCOS and 21 normal women underwent studies of frequent blood sampling and GnRH stimulation before and during insulin infusion at the General Clinical Research Center, University of California, San Diego. MAIN OUTCOME MEASURES: Group mean composite 12-h LH levels were assessed with respect to other endocrine variables. In addition, LH responses to GnRH with or without insulin infusion were assessed. RESULTS: In normal women, insulin negatively predicted mean LH. In PCOS, the combined effect of body mass index (negative) and testosterone (positive) predicted LH. The best predictor of LH was body mass index and insulin combined. Basal LH and LH responses to GnRH were unaltered by insulin infusion in normal women. These measures were reduced during insulin infusion in PCOS women. CONCLUSIONS: In PCOS, insulin infusion suppresses pituitary response to GnRH. In normal women, insulin negatively correlates with mean LH and suppresses GnRH response at a high infusion rate.     

Inverse relationship between luteinizing hormone and body mass index in polycystic ovarian syndrome: investigation of hypothalamic and pituitary contributions

CONTEXT: Patients with polycystic ovarian syndrome (PCOS) have increased LH relative to FSH, but LH is modified by body mass index (BMI). OBJECTIVE: The objective of the study was to determine whether the impact of BMI on neuroendocrine dysregulation in PCOS is mediated at the hypothalamic or pituitary level. PARTICIPANTS/INTERVENTIONS/SETTING: Twenty-four women with PCOS across a spectrum of BMIs underwent frequent blood sampling, iv administration of GnRH (75 ng/kg), and sc administration of the NAL-GLU GnRH antagonist (5 microg/kg) in the General Clinical Research Center at an academic hospital. MAIN OUTCOME MEASURES: LH pulse frequency and LH response to submaximal GnRH receptor blockade were used as measures of hypothalamic function; LH response to GnRH was used as a measure of pituitary responsiveness. RESULTS: BMI was negatively correlated with mean LH, LH/FSH, and LH pulse amplitude. There was no effect of BMI on LH pulse frequency. Percent inhibition of LH was decreased in PCOS, compared with normal women (53.9 +/- 1.5 vs. 63.1 +/- 4.1, respectively; P < 0.01), suggesting an increase in the amount of endogenous GnRH, but was not influenced by BMI. Pituitary responsiveness to GnRH was inversely correlated with BMI (peak LH, R = -0.475, P < 0.02; and LH area under the curve R = -0.412, P < 0.02). CONCLUSIONS: LH pulse frequency and quantity of GnRH are increased in PCOS, but there is no influence of BMI on either marker of hypothalamic function. The pituitary response to a weight-based dose of GnRH is inversely related to BMI in PCOS. These studies suggest that the effect of BMI on LH is mediated at a pituitary and not a hypothalamic level in PCOS.     

THE ACUTE EFFECTS OF A DOPAMINE ANTAGONIST (DOMPERIDONE) ON LUTEINISING HORMONE, FOLLICULE STIMULATING HORMONE, PROLACTIN AND THYROTROPHIN SECRETION IN POLYCYSTIC OVARIAN SYNDROME: DIFFERENTIAL EFFECT OF OVULATION

An alteration of the hypothalamic dopaminergic regulation of LH secretion has been implicated in the abnormal LH secretion of polycystic ovarian syndrome (PCOS). To investigate this, the acute effect of dopamine (DA) receptor blockade on LH, FSH, PRL and TSH secretion was determined. No effect was observed on either LH or FSH secretion in the PCOS patients or in normal women and LH pulsatility appeared to be maintained. When the PCOS patients were divided into those who ovulated in the preceding cycle and those who were anovulatory, it was observed that the ovulatory patients had a normal PRL and TSH response; whereas in the anovulatory patients, the PRL rise was blunted and the TSH response was absent. We conclude that this study gives no evidence to support the hypothesis of altered hypothalamic DA regulation of LH secretion in PCOS. The lack of LH response to DA blockade suggests that a physiological role of DA in the control of LH secretion seems unlikely as determined under these experimental conditions. The differences in PRL and TRH response may reflect anovulation rather than a fundamental abnormality in PCOS.     

Luteinizing hormone pulsatility in patients with major ovarian hyperandrogenism

Hyperandrogenism and ovulatory dysfunction are common in women with either polycystic ovary (PCOS) or ovarian virilizing tumor. However, contrasting with the numerous studies that have extensively described gonadotropin secretory abnormalities, principally increased LH pulse amplitude and frequency, few studies have concerned gonadotropin secretion in patients with ovarian virilizing tumors; low gonadotropin levels have occasionally been reported, but never extensively studied. The goal of the present study was to further evaluate the pulsatility of LH secretion in women with ovarian virilizing tumor compared with that of PCOS patients. Eighteen women with major hyperandrogenism (plasma testosterone level >1.2 ng/ml) were studied (5 women with ovarian virilizing tumor, 13 women with PCOS, and 10 control women). Mean plasma LH level, LH pulse number and amplitude were dramatically low in patients with ovarian tumors when compared to both PCOS (p<0.001) and controls (p<0.001). In case of major hyperandrogenism, LH pulse pattern differs markedly between women with ovarian virilizing tumor or PCOS, suggesting different mechanisms of hypothalamic or pituitary feedback.     

Relationship of GnRH-stimulated LH release to episodic LH secretion and baseline endocrine-metabolic measures in women with polycystic ovary syndrome

BACKGROUND AND OBJECTIVE: In polycystic ovary syndrome (PCOS) inappropriate gonadotrophin secretion is characterized by increased pulse frequency and amplitude, elevated 24-h mean serum concentrations, and greater responses to GnRH. While the mechanism(s) responsible for this increased release of LH are not well understood, enhanced LH secretion has been attributed to increased pituitary sensitivity to GnRH and feedback influences from circulating steroid hormones. To address these considerations, we conducted a study to examine the relationships between GnRH-stimulated LH responses, episodic gonadotrophin secretion, and baseline measurements of endocrine-metabolic function in PCOS. PATIENTS: Serum LH responses to sequential multidose GnRH administration and pulsatile gonadotrophin secretion were examined in 13 PCOS and 13 normal women. MEASUREMENTS: Serum LH, steroid hormone, insulin and glucose levels were determined in blood samples obtained during assessment of episodic gonadotrophin secretion and LH responses to GnRH stimulation. DESIGN: Each subject was studied on two consecutive days. On study day 1 each subject underwent frequent blood sampling every 10 min for 12 h. On study day 2 each received sequential doses of GnRH, 2 microg, 10 microg and 20 microg, administered intravenously at 4-h intervals over a continuous 12-h period. RESULTS: Serum LH responses following GnRH were markedly greater in PCOS compared to normal women, as expected. In individual PCOS, peak LH responses to GnRH were significantly correlated with corresponding basal LH and LH pulse amplitude, but not LH pulse frequency. In the PCOS group, LH responses were positively correlated with serum oestradiol (E2) and inversely related to body mass index (BMI). Between-group differences in LH responsiveness disappeared when controlling for serum testosterone (T) levels. CONCLUSIONS: These results indicate that the absolute LH increment following GnRH is largely dependent on baseline LH levels and may account for the well-documented difference in LH responsiveness between PCOS and normal women. That neither LH responses to GnRH nor LH pulse amplitude were correlated to LH pulse frequency suggests involvement of other factors along with GnRH to account for increased LH secretion in PCOS. In addition to E2 and BMI, serum testosterone appears to be, at least in part, responsible for differences in LH secretion and release between PCOS and normal women.     

Follicle luteinization in hyperandrogenic follicles of polycystic ovary syndrome patients undergoing gonadotropin therapy for in vitro fertilization

CONTEXT: Polycystic ovary syndrome (PCOS) is a reproductive disorder of ovarian hyperandrogenism and insulin resistance characterized by abnormal luteinization of small follicles. After exposure to GnRH analog/FSH stimulation for in vitro fertilization (IVF), however, it is unclear whether such PCOS follicles remain abnormally luteinized during the resumption of oocyte maturation in vivo. OBJECTIVE: The aim of this study was to determine whether PCOS follicles exposed to GnRH analog/FSH stimulation for IVF show abnormal luteinization. DESIGN: This study was a prospective cohort. SETTING: The setting was an institutional practice. Patients: Eleven PCOS and 30 normoandrogenic ovulatory women were included. INTERVENTION(S): All subjects received GnRH analog/FSH therapy after basal serum hormone determinations. MAIN OUTCOME MEASURE(S): Follicle fluid aspirated at oocyte retrieval from the first follicle of each ovary was assayed for gonadotropins, steroids, insulin, and glucose. LH receptor mRNA expression was determined in granulosa cells of the same follicle. RESULTS: In PCOS patients with basal hyperandrogenemia and hyperinsulinemia, total oocyte number was increased and follicle diameter was decreased, despite normal maximal serum estradiol levels. Within PCOS follicles, progesterone levels were reduced (P < 0.01), despite comparable bioactive LH and insulin levels and granulosa cell LH receptor mRNA expression; estradiol levels were normal, despite diminished FSH availability (P < 0.004). Elevated androstenedione (P < 0.01), testosterone (P < 0.001), and glucose (P < 0.01) levels also occurred. In PCOS follicles containing mature oocytes, however, elevated androgen levels were accompanied by both normal progesterone concentrations and a normal inverse relationship between glucose depletion and lactate accumulation. CONCLUSION: Hyperandrogenic follicles with mature oocytes from PCOS women receiving GnRH analog/recombinant human FSH therapy for IVF show sufficient glucose utilization for normal luteinization.     

Minireview: timely ovulation: circadian regulation of the female hypothalamo-pituitary-gonadal axis

The preovulatory surge in the secretion of LH is timed by a neuroendocrine integrative mechanism that involves ovarian estradiol levels and the endogenous circadian system. Studies in female rats and hamsters have established that the clock in the hypothalamic suprachiasmatic nucleus has a preeminent role in setting the LH surge, and anatomical, physiological, and pharmacological data are revealing the responsible connections between suprachiasmatic nucleus neurons and GnRH and estradiol-receptive areas. Recent investigations show that GnRH and pituitary cells express circadian clock genes that might play a role in the release and reception of the GnRH signal. Analysis of the circadian regulation of the LH surge may provide a model for understanding how multiple neural oscillators function within other neuroendocrine axes.     

Naltrexone effect on pulsatile GnRH therapy for ovulation induction in polycystic ovary syndrome: a pilot prospective study

The aim of the present study was to analyze the opioid influence on LH pulsatility in polycystic ovary syndrome (PCOS) patients and to evaluate the effectiveness of a long-term opioid antagonist (naltrexone) treatment in improving the pulsatile GnRH therapy which is successful in this syndrome. Ten obese women affected by PCOS participated in the study. Patients were hospitalized during the early follicular phase and underwent an oral glucose tolerance test (OGTT) with 75 g of glucose and a pulse pattern study followed by a GnRH test (100 pg i.v.). All patients were then treated for ovulation induction with pulsatile administration of GnRH (5 microg/bolus every 90 min). Since pregnancies did not occurr in any patient, after spontaneous or progestin-induced menstrual cycles, all patients received naltrexone at a dose of 50 mg/day orally for 8 weeks and during treatment repeated the basal protocol study and the ovulation induction cycle with the same modalities. The naltrexone treatment significantly reduced the insulin response to OGTT and the LH response to GnRH bolus, whereas it did not affect the FSH and LH pulsatility patterns. Concerning the ovulation induction by pulsatile GnRH, naltrexone treatment was able to improve, although not significantly, the ovulation rate (60% pre-treatment vs 90% post-treatment). Furthermore, the maximum diameter of the dominant follicle and the pre-ovulatory estradiol concentration were higher after long-term opioid blockade (follicular diameter 19.5+/-1.76 mm pre-treatment vs 21.6+/-2.19 mm post-treatment, p<0.001; maximum estradiol level 728.7+/-288.5 pmol/l pre-treatment vs 986.4+/-382.1 pmol/l post-treatment, p<0.05). During the naltrexone-pulsatile GnRH co-treatment two pregnancies occurred. In conclusion, our data show that naltrexone-pulsatile GnRH co-treatment is able to improve the ovarian responsiveness to ovulation induction in obese PCOS patients when compared to pulsatile GnRH alone. This action seems to be related to a decrease of insulin secretion. Further randomized studies should be performed in order to obtain significant conclusions on the possible clinical application.     

Altered multihormone synchrony in obese patients with polycystic ovary syndrome

Luteinizing hormone (LH) concentrations and pulsatility are increased in obese women with polycystic ovary syndrome (PCOS). In addition, patients have hyperandrogenemia and insulin resistance. The mechanisms involved in aberrant hormone regulation in PCOS are still unclear. We investigated 15 obese PCOS women with a body mass index between 30 and 54 kg/m² and 9 healthy obese controls (body mass index, 31-60 kg/m²) with regular menstrual cycles. Subjects underwent 24-hour blood sampling at 10-minute intervals for later measurements of LH, leptin, testosterone, and insulin concentrations. Data were analyzed with a new deconvolution program, approximate entropy (and bivariate approximate entropy), and a cross-correlation network. Patients had increased LH pulse frequency and more than 2-fold greater daily LH secretion, with diminished pattern regularity. Testosterone secretion was increased 2-fold, but pattern regularity was similar to that in controls. In the network construct, insulin was correlated positively with LH, whereas leptin and testosterone were correlated negatively with LH. Bivariate synchrony of LH with insulin was decreased. Short-term caloric restriction paradoxically increased LH secretion by 1.5-fold and pattern irregularity, and reduced interpulse variability. Testosterone secretion and fasting concentrations of estradiol and sex hormone-binding globulin levels remained unchanged. Correlations between LH and insulin, leptin, and calculated free testosterone decreased. This study demonstrates marked alterations in the control of LH secretion in PCOS in the fed and calorie-restricted states. The ensemble results point to abnormal feedback control of not only the GnRH-gonadotrope complex, but also LH's relationships with leptin, insulin, and testosterone.     

Ovarian steroids modulate neuroendocrine dysfunction in polycystic ovary syndrome

OBJECTIVE: Neuroendocrine dysfunction in polycystic ovary syndrome (PCOS) was addressed by studying the steroid hormone changes in women with PCOS with either high or normal LH levels leading to inferences regarding the primacy of elevated LH in the pathophysiology of PCOS. METHODS: A cross-sectional study was designed in an academic clinical facility involving 234 women with PCOS. Patients were divided into two groups based on an LH/FSH ratio < or >1 and hormonal and metabolic studies were performed in both groups. Factors were determined by binomial logistic regression that predicted group membership of these women. RESULTS: Higher follicular phase estradiol (E2) and androstenedione (A4) levels as well as greater insulin sensitivity were the only factors that predicted the presence of neuroendocrine dysfunction with elevated A4 being necessary for neuroendocrine dysfunction. CONCLUSIONS: It was concluded that uncoupling of hypothalamic E2 inhibition by elevated ovarian A4 associated with E2 related sensitization of pituitary LH leads to neuroendocrine dysfunction in PCOS.     

Pharmacokinetic factors contribute to the inverse relationship between luteinizing hormone and body mass index in polycystic ovarian syndrome

CONTEXT: Serum LH levels decrease with increasing body mass index (BMI) in women with polycystic ovarian syndrome (PCOS). OBJECTIVE: The objective of this study was to determine whether pharmacokinetic factors contribute to the effect of obesity on LH in PCOS. PARTICIPANTS/INTERVENTIONS/SETTING: Twenty-one women with PCOS underwent frequent blood sampling, iv administration of GnRH (75 ng/kg), and sc administration of the NAL-GLU GnRH antagonist (150 microg/kg) followed by iv recombinant human LH (rhLH; 300 IU) in the General Clinical Research Center at an academic medical center. MAIN OUTCOME MEASURES: Pharmacokinetic parameters were estimated by modeling the LH serum concentration profiles after administration of GnRH and rhLH and related to BMI. RESULTS: Serum levels of LH and rhLH decreased in a distinctly monoexponential fashion in all patients. The apparent biological half-life of rhLH was not influenced by BMI, nor was the total body clearance or apparent volume of distribution. However, the apparent half-life of endogenous LH was inversely related to BMI (r=-0.46; P<0.04), and the estimated total body clearance of endogenous LH was positively related to BMI (r=0.53; P<0.02). CONCLUSION: Estimated clearance and apparent half-life of endogenous LH are influenced by BMI in women with PCOS, contributing to the inverse relationship between LH and BMI in this population. The absence of an effect of BMI on the pharmacokinetics of rhLH in these subjects suggests that the effect of obesity on clearance of endogenous LH is the result of alterations in the isoform composition of LH secreted by the pituitary.     

Progesterone inhibition of the hypothalamic gonadotropin-releasing hormone pulse generator: evidence for varied effects in hyperandrogenemic adolescent girls

Compared with normal women, adults with polycystic ovarian syndrome (PCOS) require higher progesterone (P) concentrations to inhibit GnRH (LH) pulse frequency, which contributes to persistently rapid GnRH pulses and elevated LH levels in PCOS. To explore the origin of this abnormality, we assessed hypothalamic sensitivity to P feedback in nine normal controls and 11 hyperandrogenemic (HA) adolescents. Subjects first underwent frequent blood sampling for 11 h to assess baseline LH pulse frequency. Thereafter, oral estradiol and micronized P were given for 7 d to achieve mean estradiol and P levels of 143 +/- 16 pg/ml (524 +/- 60 pmol/liter) and 7.8 +/- 0.7 ng/ml (24.9 +/- 2.3 nmol/liter), respectively. LH pulse frequency was then reassessed. On d 7, the slope of the percent reduction of LH pulses per 11 h as a function of the d 7 P concentration was less in the HA group compared with controls (P = 0.02) despite similar P levels. LH pulse frequency was suppressed in all NC (mean, 7.0 to 3.4 pulses/11 h), but was unchanged in six of the HA girls (mean, 8.3 to 7.5 pulses/11 h). In contrast, in the other five HA adolescents, P induced similar slowing of LH pulses to that seen in NC (mean, 10.0 to 5.0 pulses/11 h). Baseline free testosterone levels were similar in both HA groups; the only observed difference between these HA groups is that the P-suppressible subjects were all of Hispanic descent. These data suggest that hyperandrogenemia during adolescence is variably associated with decreased sensitivity to P, which may have a partially genetic basis.     

Hypothalamic dysfunction

A pulsatile GnRH stimulus is required to maintain gonadotropin synthesis and secretion. The frequency and amplitude of GnRH pulses determine gonadotropin subunit gene expression and secretion of pituitary LH and FSH. Rapid frequency (more than 1 pulse per h) GnRH pulses favor LH while slower frequencies favor FSH secretion. During ovulatory cycles, an increase in GnRH frequency during the follicular phase favors LH synthesis prior to the LH surge, while following ovulation, luteal steroids slow GnRH pulses to favor FSH synthesis. Thus, a changing frequency of GnRH stimulation of the gonadotrope is one of the mechanisms involved in differential gonadotropin secretion during ovulatory cycles. In hypothalamic amenorrhea a majority of women exhibit a persistent slow frequency of LH (GnRH) pulses, which reflects excess hypothalamic opioid tone and can be temporarily reversed by opioid antagonists. At the other end of the spectrum, in polycystic ovarian syndrome, LH (GnRH) pulses are persistently rapid and favor LH synthesis, hyperandrogenism and impaired follicular maturation. Administration of progesterone can slow GnRH pulse secretion, favor FSH secretion and induce follicular maturation. Thus, the ability to change the pattern of GnRH secretion is an important factor in the maintenance of cyclic ovulation, and loss of this function leads to anovulation and amenorrhea.     

Impairment of the opioidergic control of luteinizing hormone secretion in Turner's syndrome: lack of effect of gonadal steroid therapy

We studied the activity of endogenous opioid peptides in regulating LH secretion in patients with Turner's syndrome. To do so, we determined the LH secretory response to opiate receptor blockade by naloxone (0.08 mg/kg BW, iv) in 17 patients (age range, 9-23 yr). Eight patients were untreated (3 of whom had had spontaneous menarche), and 9 patients were taking ethinyl estradiol/medroxyprogesterone acetate treatment (5 of these patients were also studied before treatment). In addition, the plasma LH responses to GnRH (50 micrograms, iv) and placebo were determined in the patients as well as in 13 age-matched normal girls (6 prepubertal and 7 pubertal). Naloxone did not increase plasma LH levels in the amenorrheic untreated and treated patients with Turner's syndrome. However, in the 3 patients who had had spontaneous menarche and in normal pubertal girls naloxone increased plasma LH levels. GnRH was effective to the same extent in the patients and normal subjects. These results indicate that in patients with Turner's syndrome the opioidergic inhibition of LH secretion is impaired and is not restored by gonadal steroid replacement therapy. Moreover, the normal plasma LH responses to naloxone in the spontaneously menstruating patients with Turner's syndrome indicate both the clinical variability of this syndrome and the participation of endogenous opioid peptides in the regulation of normal menstrual function.     

Enhancement of a robust arcuate GABAergic input to gonadotropin-releasing hormone neurons in a model of polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS), the leading cause of female infertility, is associated with an increase in luteinizing hormone (LH) pulse frequency, implicating abnormal steroid hormone feedback to gonadotropin-releasing hormone (GnRH) neurons. This study investigated whether modifications in the synaptically connected neuronal network of GnRH neurons could account for this pathology. The PCOS phenotype was induced in mice following prenatal androgen (PNA) exposure. Serial blood sampling confirmed that PNA elicits increased LH pulse frequency and impaired progesterone negative feedback in adult females, mimicking the neuroendocrine abnormalities of the clinical syndrome. Imaging of GnRH neurons revealed greater dendritic spine density that correlated with increased putative GABAergic but not glutamatergic inputs in PNA mice. Mapping of steroid hormone receptor expression revealed that PNA mice had 59% fewer progesterone receptor-expressing cells in the arcuate nucleus of the hypothalamus (ARN). To address whether increased GABA innervation to GnRH neurons originates in the ARN, a viral-mediated Cre-lox approach was taken to trace the projections of ARN GABA neurons in vivo. Remarkably, projections from ARN GABAergic neurons heavily contacted and even bundled with GnRH neuron dendrites, and the density of fibers apposing GnRH neurons was even greater in PNA mice (56%). Additionally, this ARN GABA population showed significantly less colocalization with progesterone receptor in PNA animals compared with controls. Together, these data describe a robust GABAergic circuit originating in the ARN that is enhanced in a model of PCOS and may underpin the neuroendocrine pathophysiology of the syndrome.Gonadotropin-releasing hormone (GnRH) neurons, located in the hypothalamus, control fertility by driving the secretion of the gonadotrophins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) from the pituitary gland. The pulse amplitude and frequency of LH and FSH shape the sequence of events that occur at the ovary, including follicular development, gonadal steroid synthesis, and ovulation. Hormones secreted from the ovary, in turn, provide critical feedback signals to GnRH neurons through a network of hormone-sensitive neurons. Gonadal hormone feedback directs both the firing of GnRH neurons and pulsatile release of the GnRH peptide (1).Polycystic ovarian syndrome (PCOS), the most common form of anovulatory infertility (2), is estimated to affect more than 100 million women worldwide (3). Most women diagnosed with PCOS exhibit increased LH pulse frequency and decreased FSH release, suggestive of rapid GnRH pulse frequency (4). High LH, in turn, contributes to increased androgen production from ovarian theca cells, whereas decreased FSH disrupts follicle maturation and ovulation. Elevated GnRH/LH secretion in women with PCOS is less responsive to exogenous estrogen and progesterone (P4) administration (5, 6), suggesting that steroid hormone negative feedback to GnRH neurons is impaired. In animal models, elevated androgens are associated with blunted P4 negative feedback in particular (7, 8).Although the origin of GnRH/LH hypersecretion in PCOS is unknown, impaired steroid hormone negative feedback may lie within the hormone-sensitive afferent neuronal network to GnRH neurons. Identifying the specific neuronal elements affected is challenging in women; however, discoveries can be made in animal models (9, 10). PCOS is most commonly modeled through exposure to androgens during critical periods of development (11). Women exposed to elevated prenatal androgens (PNAs) develop the cardinal reproductive and endocrine features of PCOS in adulthood (12, 13), and PNA treatment produces a PCOS-like phenotype in all mammalian species studied to date (11). In the mouse, PNA elicits many of the key neuroendocrine features of the syndrome, suggestive of impaired steroid hormone feedback to the GnRH pulse generator (14, 15), however, it remains to be determined directly whether P4 negative feedback and LH pulse frequency are modified.P4 modulation of GnRH neurons via classical progesterone receptors (PRs) is most likely transsynaptic, as GnRH neurons do not express PRs. Many P4-sensitive populations have been identified throughout the hypothalamus, including neurons expressing gamma-aminobutyric acid (GABA) (16), glutamate (17), and various neuropeptides (18, 19). Both endogenous GnRH neuron firing activity and GABAergic postsynaptic currents are increased in PNA mice (15, 20). However, the specific P4-sensitive neuronal phenotype that relays feedback signals to GnRH neurons is so far unknown. The aim of the present study was to characterize whether LH pulse frequency and P4 negative feedback are impaired in a mouse model of PCOS and to investigate what modifications exist in the GnRH neuronal network that may impair negative feedback.     

LH suppression following different low doses of the GnRH antagonist ganirelix in polycystic ovary syndrome

Elevated LH concentration is a common feature in polycystic ovary syndrome (PCOS). This study was designed to establish whether elevated LH levels in PCOS might be suppressed to normal range values by the administration of different low doses of GnRH antagonist, which subsequently might reverse the anovulatory status of these patients. Twenty-four PCOS patients with elevated endogenous LH concentrations were randomized into 3 different dose groups, receiving either 0.125 mg (Group A), 0.250 mg (Group B) or 0.500 mg (Group C) ganirelix sc daily for 7 subsequent days. During the first day of treatment, LH and FSH levels were assessed at 20 min intervals, during 8 h. Thereafter LH, FSH, androgens, estradiol (E2) and inhibins were assessed daily and frequent ultrasound scans were performed for 7 days to record follicle development. Repeated GnRH antagonist administration induced a significant suppression of LH (and to a lesser extent of FSH) serum levels, which was comparable between the different doses. Six hours after ganirelix administration, endogenous LH was suppressed by 49, 69 and 75%, and endogenous FSH was suppressed by 23, 19 and 25%, respectively. The decrease in serum LH and FSH levels was transient and lasted for 12 h, after which serum levels returned to baseline levels at 24 h after drug administration. Androgen levels were not significantly suppressed using this regimen. E2 levels decreased significantly (p < 0.001) and suppression was most pronounced in Group C. Spontaneous follicle development or ovulations were not recorded during the course of treatment. In conclusion, the present study demonstrates that the GnRH antagonist ganirelix is capable of normalising elevated LH levels in PCOS patients, in doses similar to the ones previously shown to prevent a premature LH rise during ovarian hyperstimulation for in vitro fertilization (IVF). In addition, the transient suppression of elevated endogenous LH levels per se does not re-establish normal follicle development in PCOS. However, follicle development may be insufficiently supported by the accompanied subtle suppression of endogenous FSH. Similarly, a transient decline in E2 levels does not effectively restore normal pituitary ovarian feedback. Moreover, these results support the contention of a limited role of LH in the pathogenesis of PCOS.     

The effects of metformin on insulin resistance and ovarian steroidogenesis in women with polycystic ovary syndrome

OBJECTIVE: Polycystic ovary syndrome (PCOS) is a form of functional ovarian hyperandrogenism and affects approximately 5-10% of women of reproductive age. Insulin resistance and hyperinsulinaemia appear to be almost universal feature of the polycystic ovary syndrome. Abnormal regulation of cytochrome P450c17alpha causes the exaggerated secretion of ovarian androgens in PCOS. The aim of the present study was to determine whether reduction of insulin levels by metformin would attenuate FSH, LH, 17-Hydroxyprogesterone (17-OHP) and androstenedione hyperresponsiveness to buserelin testing in PCOS women. DESIGN: The presence of hyperinsulinaemia in 16 women with PCOS was demonstrated by an oral glucose tolerance test (OGTT) and results were compared with 13 healthy women. PCOS women were also evaluated with insulin tolerance test (ITT) for the assessment of insulin sensitivity. FSH, LH, 17-OHP and androstenedione responses to buserelin testing were measured in all the women with PCOS. PCOS patients were given metformin (500 mg, orally, two times daily) for 12 weeks and re-evaluated at the end of the treatment period. RESULTS: Women with PCOS were hyperinsulinaemic (basal insulin 92.1+/-14.3 vs. 44.0+/-4.0 pmol/l; AUCinsulin 68087.4+/-8862.3 vs. 13075.5+/-1327.6 pmol/lx120 min) compared with healthy women. Metformin therapy improved menstrual disturbances in 25% of the women with PCOS and also resulted in some improvement in insulin sensitivity and reduced basal and post glucose load insulin levels. However, FSH, LH, 17-OHP and androstenedione responses to buserelin testing were unaltered in response to metformin. CONCLUSION: It is clear that PCOS is often associated with profound insulin resistance and hyperinsulinaemia. These abnormalities explain the increased prevalence of glucose intolerance in women with PCOS and metformin has beneficial effects on insulin sensitivity in women with PCOS. Amelioration of hyperinsulinaemia has no significant effect on ovarian cytochrome P450c17alpha enzyme activity. However, it can be used in obese women with PCOS as an adjuvant therapy and long term studies should be performed to evaluate the endocrine effects of metformin in women with PCOS.     

Luteinizing hormone secretion is not influenced by insulin infusion in women with polycystic ovary syndrome despite improved insulin sensitivity during pioglitazone treatment

It has been reported in women with polycystic ovary syndrome (PCOS) that LH secretion is not altered by insulin infusion. To determine whether insulin resistance may have precluded an effect of insulin, pulsatile LH secretion and gonadotropin responses to GnRH were examined in PCOS women (n = 9) before and after pioglitazone treatment (45 mg/d) for 20 wk in the presence and absence of a hyperinsulinemic euglycemic clamp (80 mU/m2.min). Frequent blood samples were obtained for 12 h (every 10 min) as well as during sequential administration of GnRH at doses of 2, 10, and 20 microg over 12 h. A significant (P < 0.05) improvement in insulin sensitivity was seen in the subjects after treatment. Mean LH levels, LH pulse frequency and amplitude, as well as gonadotropin responses to GnRH were not influenced by pioglitazone, either with or without insulin infusion. We conclude that in PCOS women, inappropriate gonadotropin release does not appear to be a consequence of hyperinsulinemia.     

Pituitary-ovarian response to the gonadotrophin-releasing hormone-agonist test in anovulatory patients with polycystic ovary syndrome: predictive role of ovarian stroma

Objective To evaluate the influence of ovarian stroma on basal and poststimulus androgen secretion in patients affected by secondary amenorrhoea and polycystic ovaries (PCO) at ultrasound (US). Design Prospective study. Patients Fifty‐one patients with PCO selected from a group of 72 normal weight women aged 20–25 years affected by secondary amenorrhoea and 10 normal ovulatory controls. Methods All subjects underwent US to evaluate volume, area, stromal area and stromal/total area ratio of both ovaries. Plasma levels of gonadotrophins, oestradiol (E2) and androgens were measured before and 24 h after GnRH‐a injection. 60 min after stimulus LH and FSH were also assayed. Results Thirty patients had increased ovarian stroma (IS) and 21 patients normal ovarian stroma (NS). Significantly higher LH levels characterized the IS group, both basally and after GnRH‐a stimulation compared with NS and controls (P < 0·01). Baseline levels of androstenedione, testosterone and 17‐OHprogesterone (17‐OHP) were significantly higher in IS group. Moreover, 17‐OHP hyper‐response to GnRH‐a was demonstrated in IS group in comparison to NS and control groups (P < 0·005). Conclusions Stroma evaluation may be of use in discriminating between different pathogenic factors in secondary amenorrhoea. This criterion may be applied to support the correct diagnosis of polycystic ovary syndrome (PCOS). Indeed, in line with the most recently proposed guidelines, patients affected by multifollicular ovaries could be classified as PCOS. The possibility of taking into account more than one US criterion or of carefully reanalysing the significance of increased stroma volume should be considered.