Follicle-stimulating Hormone Surge Research Articles

FSH Is Responsible for Androgen Deprivation Therapy-Associated Atherosclerosis in Mice by Exaggerating Endothelial Inflammation and Monocyte Adhesion.

Androgen deprivation therapy (ADT) is the mainstay treatment for advanced prostate cancer. But ADTs with orchiectomy and gonadotropin-releasing hormone (GnRH) agonist are associated with increased risk of cardiovascular diseases, which appears less significant with GnRH antagonist. The difference of follicle-stimulating hormone (FSH) in ADT modalities is hypothesized to be responsible for ADT-associated cardiovascular diseases. We administered orchiectomy, GnRH agonist, or GnRH antagonist in male ApoE-/- mice fed with Western diet and manipulated FSH levels by testosterone and FSH supplementation or FSH antibody to investigate the role of FSH elevation on atherosclerosis. By combining lipidomics, in vitro study, and intraluminal FSHR (FSH receptor) inhibition, we delineated the effects of FSH on endothelium and monocytes and the underlying mechanisms. Orchiectomy and GnRH agonist, but not GnRH antagonist, induced long- or short-term FSH elevation and significantly accelerated atherogenesis. In orchiectomized and testosterone-supplemented mice, FSH exposure increased atherosclerosis. In GnRH agonist-treated mice, blocking of short FSH surge by anti-FSHβ antibody greatly alleviated endothelial inflammation and delayed atherogenesis. In GnRH antagonist-treated mice, FSH supplementation aggravated atherogenesis. Mechanistically, FSH, synergizing with TNF-α (tumor necrosis factor alpha), exacerbated endothelial inflammation by elevating VCAM-1 (vascular cell adhesion protein 1) expression through the cAMP/PKA (protein kinase A)/CREB (cAMP response element-binding protein)/c-Jun and PI3K (phosphatidylinositol 3 kinase)/AKT (protein kinase B)/GSK-3β (glycogen synthase kinase 3 beta)/GATA-6 (GATA-binding protein 6) pathways. In monocytes, FSH upregulated CD29 (cluster of differentiation 29) expression via the PI3K/AKT/GSK-3β/SP1 (specificity protein 1) pathway and promoted monocyte-endothelial adhesion both in vitro and in vivo. Importantly, FSHR knockdown by shRNA in endothelium of carotid arteries markedly reduced GnRH agonist-induced endothelial inflammation and atherosclerosis in mice. FSH is responsible for ADT-associated atherosclerosis by exaggerating endothelial inflammation and promoting monocyte-endothelial adhesion.

Pattern of gonadotropin secretion along the estrous cycle of C57BL/6 female mice

The pattern of gonadotropin secretion along the estrous cycle was elegantly described in rats. Less information exists about the pattern of gonadotropin secretion in gonad‐intact mice, particularly regarding the follicle‐stimulating hormone (FSH). Using serial blood collections from the tail‐tip of gonad‐intact C57BL/6 mice on the first day of cornification (transition from diestrus to estrus; hereafter called proestrus), we observed that the luteinizing hormone (LH) and FSH surge cannot be consistently detected since only one out of eight females (12%) showed increased LH levels. In contrast, a high percentage of mice (15 out of 21 animals; 71%) exhibited LH and FSH surges on the proestrus when a single serum sample was collected. Mice that exhibited LH and FSH surges on the proestrus showed c‐Fos expression in gonadotropin‐releasing hormone‐ (GnRH; 83.4% of co‐localization) and kisspeptin‐expressing neurons (42.3% of co‐localization) of the anteroventral periventricular nucleus (AVPV). Noteworthy, mice perfused on proestrus, but that failed to exhibit LH surge, showed a smaller, but significant expression of c‐Fos in GnRH (32.7%) and AVPVKisspeptin (14.0%) neurons. Finally, 96 serial blood samples were collected hourly in eight regular cycling C57BL/6 females to describe the pattern of LH and FSH secretion along the estrous cycle. Small elevations in LH and FSH levels were detected at the time expected for the LH surge. In summary, the present study improves our understanding of the pattern of gonadotropin secretion and the activation of central components of the hypothalamic–pituitary‐gonadal axis along the estrous cycle of C57BL/6 female mice.

Effect of ovarian follicular wave pattern and endocrine characteristics on pregnancy outcome in cows.

The effect of two (2W) versus three (3W) wave patterns of follicular dynamics and concurrent endocrine milieu of follicle-stimulating hormone (FSH), luteinizing hormone (LH), oestradiol 17-β (E2) and progesterone (P4) were investigated during one interoestrous interval (IEI) before insemination, on ensuing pregnancy, in 70 lactating Jersey crossbred cows. The findings were evaluated for between [included all (overall) 2W-O and 3W-O cows] and within [after separating pregnant (P) and non-pregnant (NP) cows in 2W and 3W] wave patterns. The propensity of two (58.6%, n=41) and three (41.4%, n=29) wave patterns was similar (p=.15). The IEI, shorter by 2.6days for 2W-O versus 3W-O (p<.0009), predicted wave pattern as 100% 2W-O cows had IEI of ≤21days, present only in 27.6% 3W-O cows (p<.0001). The ovulatory follicle persisted for a significantly shorter duration for 3W-O versus 2W-O cows. The average FSH, LH, E2 and P4 concentrations during the IEI did not differ for between and within the wave patterns. Pregnancy rate (%) of 58.6 versus 41.4 (p=.15) for 2W-O versus 3W-O and 56.1-P versus 43.9-NP (p=.44) for within 2W was similar, but tended to differ for within the 3W pattern (69.0-P versus 31.0-NP, p=.06). The pregnancy outcome was influenced by the age of ovulatory follicle for between the wave patterns and by follicular count as well as FSH surge concentration for within the wave patterns. A shorter luteal phase reduced the pregnancy outcome, a novel finding of the present study.

Suboptimal response to GnRH agonist trigger: causes and practical management.

GnRH agonist products are used extensively worldwide to trigger ovulation and final oocyte maturation in in vitro fertilization cycles. The purpose of this article is to outline possible causes for a suboptimal response to the GnRH agonist trigger. Risk factors for such a suboptimal response include prolonged hormonal contraceptive use, previous GnRHa-induced pituitary downregulation, a hypogonadotropic/hypogonadal condition, patient error, environmental conditions that may damage the GnRHa product used, GnRH and luteinizing hormone (LH) receptors polymorphisms, low baseline LH and low endogenous serum LH levels on trigger day as well as low BMI. The induction of an adequate LH surge can be ascertained by an LH urine test 12 h post trigger. In most cases, GnRHa trigger elicits effective LH+follicle stimulating hormone surges, resulting in mature, fertilizable oocytes. Clinical awareness to conditions that may predispose to a suboptimal response to the GnRHa trigger may prevent failed oocyte retrial.

To Compare the Effect of GnRH Agonist versus Human Chorionic Gonadotropin (HCG) Trigger on Clinical Pregnancy Rate in Intrauterine Insemination Cycle.

Context:Gonadotropin-releasing hormone (GnRH) agonist trigger mimics the natural surge more closely with both luteinizing hormone (LH) and follicle-stimulating hormone surge. The present study attempts to find whether this apparent physiological advantage translates into the better pregnancy rate.Aims:To compare the effect of GnRH agonist versus human chorionic gonadotropin (hCG) trigger on the clinical pregnancy rate (CPR) in infertile women undergoing intrauterine insemination (IUI) with oral ovulogens.Settings and Design:Retrospective analysis at a tertiary care in vitro fertilization center.Materials and Methods:The records of 280 infertile women, who underwent IUI with oral ovulogens were analyzed. Women who received 0.2 mg triptorelin (GnRH agonist (GnRHa)) as trigger were categorised in Group A (n = 129) and those who received 10,000 IU urinary hCG in Group B (n = 151). The outcome in terms of CPR was studied.Statistical Analysis Used:The quantitative variables were compared using the independent t-test/Mann–Whitney test. The qualitative variables were compared using the Chi-square test. P < 0.05 was considered statistically significant.Results:There was a trend toward better CPR in Group A (21/129 – 16.28%) than in Group B (16/151 – 10.60%), although the difference was not found to be statistically significant (P – 0.162).Conclusions:There was a trend toward better CPR with the use of GnRH agonist trigger in IUI cycles with oral ovulogens in comparison to hCG trigger, although the difference was not found to be statistically significant. Further randomized controlled trials are needed to confirm these findings.

SAT-417 The Gonadotrope Leptin Signal Is Critical for the Early-Morning Estrus Rise in FSH in Female Mice

The importance of peripheral nutritional signals to the functioning of the reproductive axis is appreciated, but the mechanisms are not well understood. The three tiers of the hypothalamic-pituitary-gonadal axis are receptive to many of these nutritional signals, including leptin. We have previously shown that leptin communicates with pituitary gonadotropes to maintain numbers of gonadotropin-releasing-hormone receptors (GnRHrs), and that loss of the leptin signal (LEPR) in gonadotropes results in subfertility in females. Using our current model of gonadotrope leptin resistance (GnRHR-cre, floxed Lepr exon 1) which targets the deletion of all LEPRs specifically to gonadotropes expressing Gnrhr, we investigated the role of leptin in the follicle-stimulating hormone (FSH) surge in female mice. Pituitaries and serum from 2-3 month-old control (CTL) and gonadotrope-Lepr-null (MUT) females were collected at midnight between proestrus and estrus, and at 0400 and 0900 on the morning of estrus. The samples were assayed for LH and FSH, and pituitaries were also used to determine GnRHr levels (ELISA) and Lh, Fsh, and Gnrhr mRNA levels (qPCR). Our gonadotrope-Lepr-null females showed a dramatic decrease in serum FSH during the peak of FSH secretion (0400 estrus, CTL: 25.8 ng/mL ± 5.7, n=6, MUT: 6.9 ng/mL ± 0.8, n=5, p<0.03). This result is significant, despite the large natural variability in gonadotropin surges. MUT FSH secretion also trended down at midnight by about 40%, although this effect was not significant. Interestingly, stores of FSH at 0400 were significantly increased in MUT pituitaries compared to controls. Control FSH stores dropped by ~74% from midnight to 0400, whereas mutant stores only dropped about 14% in the same time period, suggesting that the mutants have insufficient FSH secretion beginning at midnight. Analyses of ovarian sections from diestrous or proestrous MUT females showed a significant 38-43% decline in the average number of antral follicles (ANOVA, p<0.05 n=7-8), which correlates with the low FSH secretion. We also discovered a major drop in Fsh mRNA in our MUT pituitaries at 0400 (CTL RQ: 0.68 ± 0.14, n=5; MUT RQ: 0.10 ± 0.04, n=6, p<0.02). MUT Fsh mRNA remained low at 0900 (NS), at about 40% of control mRNA. Importantly, despite finding GnRHR proteins decreased at other stages in the cycle, no differences were seen between controls and mutants with regards to GnRHR (protein or mRNA) during these specific FSH surge time points. Our study indicates that leptin signals to the reproductive axis through control of FSH secretion specifically during the time of the FSH surge in female mice. We hypothesize that leptin may also be able to regulate Fsh transcription. Future studies will test the ability of leptin to stimulate Fsh transcription and secretion from normal, early AM estrous pituitaries and will investigate the pathways that mediate these effects.

Systemic effect of follicle-stimulating hormone and intraovarian effect of the corpus luteum on complete regression vs recovery of regressing wave-2 follicles in heifers

Each subordinate of the second follicular wave (wave 2) was monitored, and the outcome was classified as fully regressed (decreased in diameter to 2 mm) or recovered (decreased initially and then increased to become a growing follicle of the subsequent wave 1). The changing diameter of each follicle after emergence at 2 mm and plasma concentration of follicle-stimulating hormone were determined every 12 h from the day of ovulation (Day 0) to 4 d after the subsequent ovulation in heifers with 2 follicular waves per interovulatory interval (n = 10). The number and percentage of wave-2 subordinates that initially regressed and then recovered (7.2 ± 1.0 follicles; 33.2 ± 5.1%) were less (P < 0.0008) than the number and percentage that completely regressed (15.0 ± 1.7; 66.8 ± 5.1%). Follicles that later recovered initially reached maximal diameter on a later day (P < 0.0001) after emergence at 2 mm (4.3 ± 0.2 d) and at a larger (P < 0.0001) diameter (5.8 ± 0.2 mm) than follicles that completely regressed (3.2 ± 0.1 d; 4.7 ± 0.1 mm). The follicle-stimulating hormone surge that stimulated wave 2 began earlier and was more sustained in a subgroup with a high percentage of recovered follicles (61%) than in a subgroup with a low percentage (24%). Recovery began on Day −1.0 ± 0.1 when the follicles had regressed to 3.7 ± 0.1 mm. Diameter of subordinate follicles on Day −6 or before the expected days of luteolysis was greater (P < 0.05) when in the corpus luteum (CL) ovary than when in the non-CL ovary. During expected luteolysis, more follicles (P < 0.008) per ovary continued to regress when ipsilateral to the CL (9.2 ± 1.1 follicles) than when contralateral (5.8 ± 1.1), and more follicles (P < 0.02) recovered from regression when contralateral to the CL (5.0 ± 0.8) than when ipsilateral (2.2 ± 0.6). The hypothesis that the CL has a local effect on the development, regression, and recovery of the subordinate follicles of wave 2 was supported.

Nociceptin and meiosis during spermatogenesis in postnatal testes.

Phosphorylated Rec8, a key component of cohesin, mediates the association and disassociation, "dynamics," of chromosomes occurring in synaptonemal complex formation, crossover recombination, and sister chromatid cohesion during meiosis in germ cells. Yet, the extrinsic factors triggering meiotic chromosome dynamics remained unclear. In postnatal testes, follicle-stimulating hormone (FSH) acts directly on somatic Sertoli cells to activate gene expression via an intracellular signaling pathway composed of cAMP, cAMP-dependent protein kinase (PKA), and cAMP-response element-binding protein (CREB), and promotes germ cell development and spermatogenesis indirectly. Yet, the paracrine factors mediating the FSH effects to germ cells remained elusive. We have shown that nociceptin, known as a neuropeptide, is upregulated by FSH signaling through cAMP/PKA/CREB pathway in Sertoli cells of postnatal murine testes. Chromatin immunoprecipitation from Sertoli cells demonstrated that CREB phosphorylated at Ser133 associates with prepronociceptin gene encoding nociceptin. Analyses with Sertoli cells and testes revealed that both prepronociceptin mRNA and the nociceptin peptide are induced after FSH signaling is activated. In addition, the nociceptin peptide is induced in testes after 9 days post partum following FSH surge. Thus, our findings may identify nociceptin as a novel paracrine mediator of the FSH effects in the regulation of spermatogenesis; however, very little has known about the functional role of nociceptin in spermatogenesis. We have shown that nociceptin induces Rec8 phosphorylation, triggering chromosome dynamics, during meiosis in spermatocytes of postnatal murine testes. The nociceptin receptor Oprl-1 is exclusively expressed in the plasma membrane of testicular germ cells, mostly spermatocytes. Treatment of testes with nociceptin resulted in a rapid phosphorylation of Rec8. Injection of nociceptin into mice stimulated Rec8 phosphorylation and meiotic chromosome dynamics in testes, whereas injection of nocistatin, a specific inhibitor for nociceptin, abolished them. Therefore, our findings suggest that nociceptin is a novel extrinsic factor that plays a crucial role in the progress of meiosis during spermatogenesis.

Effects of unilaterally microinjecting ethanol in the preoptic-anterior hypothalamic areas of rats on ovulation.

Intragastric or intraperitoneal ethanol (EtOH) treatment inhibits reproductive functions in females and male rats. The area of the hypothalamus where these effects take place is unknown. As the participations of the preoptic-anterior hypothalamic area (POA-AHA) in regulating ovulation is asymmetric, this study aims to analyze the effects on 17β-estradiol(E2 ), progesterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) serum levels, the messenger ribonucleic acid (mRNA) expression of estrogen receptor alpha (ERα) and beta (ERβ), and ovulation resulting from unilaterally microinjecting water or an EtOH solution into either side of the POA-AHA. The treatment consisted of microinjecting a 8.6 μM EtOH solution into either side of the POA-AHA. The study was performed on groups of adult cyclic rats at 09.00 hours on diestrus-1, and sacrificed on diestrus-2 at 13.00, on proestrus at 09.00 or 17.00 or on estrus at 09.00 hours. Ovulation rates were assessed in rats sacrificed on estrus. Hormonal serum levels were measured using radioimmunoassay, and as a function of ERα and ERβ mRNA expression in each side of the POA-AHA by reverse transcriptase polymerase chain reaction. EtOH treatment blocked ovulation and the preovulatory release of LH, and lowered E2 levels. Irrespective of the treated POA-AHA side, ERα mRNA expression was consistently lower in the left POA-AHA and higher on the right. EtOH treatment in the left POA-AHA decreased FSH serum levels and lowered ERβ mRNA expression. In turn, EtOH treatment on the right POA-AHA resulted in higher FSH levels and ERβ mRNA expression. The present results show that EtOH blocks the preovulatory surge of LH on the POA-AHA. The effects of EtOH treatment of preovulatory FSH surge on the POA-AHA are asymmetric (stimulative on the right and inhibiting in the left). The effects of EtOH treatment on preovulatory LH and FSH surge could be explained by the inhibition of ERα and ERβ mRNA expression, respectively.

Gonadotropin-Releasing Hormone, Estradiol, and Inhibin Regulation of Follicle-Stimulating Hormone and Luteinizing Hormone Surges: Implications for Follicle Emergence and Selection in Heifers

Mechanisms regulating gonadotropin surges and gonadotropin requirements for follicle emergence and selection were studied in heifers. Experiment 1 evaluated whether follicular inhibins regulate the preovulatory luteinizing hormone (LH)/follicle-stimulating hormone (FSH) surges elicited by gonadotropin-releasing hormone (GnRH) injection (Hour = 0) and the subsequent periovulatory FSH surge. Treatments included control (n = 6), steroid-depleted bovine follicular fluid (bFF) at Hour -4 (n = 6), and bFF at Hour 6 (n = 6). Gonadotropins in blood were assessed hourly from Hours -6 to 36, and follicle growth tracked by ultrasound. Consistent with inhibin independence, bFF at Hour -4 did not impact the GnRH-induced preovulatory FSH surge, whereas treatment at Hour 6 delayed onset of the periovulatory FSH surge and impeded growth of a new follicular wave. Experiment 2 examined GnRH and estradiol (E2) regulation of the periovulatory FSH surge. Treatment groups were control (n = 8), GnRH-receptor antagonist (GnRHr-ant, n = 8), and E2 + GnRHr-ant (n = 4). GnRHr-ant (acyline) did not reduce the concentrations of FSH during the periovulatory surge and early follicle development (<7.0 mm) was unaffected, although subsequent growth of a dominant follicle (>8.0 mm) was prevented by GnRHr-ant. Addition of E2 delayed both the onset of the periovulatory FSH surge and emergence of a follicular wave. Failure to select a dominant follicle in the GnRHr-ant group was associated with reduced concentrations of LH but not FSH. Maximum diameter of F1 in controls (13.3 ± 0.5 mm) was greater than in both GnRHr-ant (7.7 ± 0.3 mm) and E2 + GnRHr-ant (6.7 ± 0.8 mm) groups. Results indicated that the periovulatory FSH surge stems from removal of negative stimuli (follicular E2 and inhibin), but is independent of GnRH stimulation. Emergence and early growth of follicles (until about 8 mm) requires the periovulatory FSH surge but not LH pulses. However, follicular deviation and late-stage growth of a single dominant follicle requires GnRH-dependent LH pulses.

Postnatal Developmental Changes in the Pituitary-Ovarian Axis in Preterm and Term Infant Girls

The period of postnatal pituitary activation has been well characterized in infant boys and is considered to be an important phase in future reproductive development. However, the possible importance of this activation in future female reproductive development is not understood. A number of clinical markers, including serum follicle-stimulating hormone (FSH) and anti-Múllerian hormone (AMH) levels, and the antral follicle count (visualized by ultrasonography) play a role in postnatal pituitary activation. Serum AMH levels strongly correlate with the antral follicle count in the follicular phase of the menstrual cycle. This longitudinal study compared postnatal developmental changes in the pituitary -ovarian axis in full-term and premature infant girls. A total of 63 infant girls were divided into the following 3 cohorts according to gestational age (GA) at birth: full term (FT; n = 29; GA, 37–42 weeks), near term (NT; n = 17; GA, 34–37 weeks), and preterm (PT; n = 17; GA, 25–34 weeks). Examinations were performed during the first week of life (D7), with subsequent monthly follow-up to 6 months of chronological age (M1–M6) and reexaminations at the corrected age of 14 months (cM14). The primary study outcome measures assessed at the follow-up examinations were levels of urinary FSH and serum AMH and the number of antral follicles. The postnatal FSH surge was significantly stronger and more prolonged among both NT and PT girls compared with FT girls (P ≤ 0.001). A rise in levels of AMH and increased folliculogenesis occurred in all 3 groups after the FSH surge. There was a delay among both NT and PT girls in follicular development compared with FT girls, with a temporal association between a decrease in the high FSH levels around the 40th postmenstrual week and the ultrasonographic appearance of antral follicles and increased AMH levels. These findings demonstrate a temporal relationship between the postnatal FSH surge and transient ovarian stimulation in term and PT girls. The strong FSH surge in premature girls may result from delayed ovarian folliculogenesis shown by the absence of antral follicles and low AMH levels.

Nociceptin is upregulated by FSH signaling in Sertoli cells in murine testes

In postnatal testes, follicle-stimulating hormone (FSH) acts on somatic Sertoli cells to activate gene expression directly via an intracellular signaling pathway composed of cAMP, cAMP-dependent protein kinase (PKA), and cAMP-response element-binding protein (CREB), and promotes germ cell development indirectly. Yet, the paracrine factors mediating the FSH effects to germ cells remained elusive. Here we show that nociceptin, known as a neuropeptide, is upregulated by FSH through cAMP/PKA/CREB pathway in Sertoli cells in murine testes. Chromatin immunoprecipitation from Sertoli cells shows that CREB phosphorylated at Ser133 associates with prepronociceptin gene encoding nociceptin. Analyses with Sertoli cells and testes demonstrates that both prepronociceptin mRNA and the nociceptin peptide are induced after FSH signaling is activated. In addition, the nociceptin peptide is induced in testes after 9days post partum following FSH surge. Thus, our findings may identify nociceptin as a novel paracrine mediator of the FSH effects in the regulation of spermatogenesis.

The CRH-R1 receptor mediates luteinizing hormone, prolactin, corticosterone and progesterone secretion induced by restraint stress in estrogen-primed rats

Acute stress has been shown to modify hypothalamus–pituitary–gonadal (HPG) axis activity. Corticotropin-releasing hormone (CRH), the principal regulator of the hypothalamus–pituitary–adrenal (HPA) axis, has been implicated as a mediator of stress-induced effects on the reproductive axis. The role of the specific CRH receptor subtypes in this response is not completely understood. In the current study, we investigated the role of the CRH-R1 receptor on luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), progesterone (P) and corticosterone (CT) secretion in stress-induced responses under the influence of estrogen (E2). Estrogen-primed ovariectomized rats (estradiol cypionate, 10μg sc) received an i.v. administration of antalarmin (0.1 or 1mg/kg), a selective CRH-R1 antagonist, or vehicle before restraint stress for 40min. Seven blood samples were collected from two experimental groups (one from 10:00h to 14:00h and the other from 10:00h to 18:00h). An increase of plasma LH induced by restraint acute-stress was followed by alteration of the secretion pattern in the estrogen-induced afternoon surge. In a similar manner, we observed a suppression of the afternoon surge in plasma FSH, a delay of E2-induced PRL secretion, and an increase in plasma P and CT. Antalarmin attenuated stress-induce LH increase, decreased CT and P secretion and blocked the stress effects on PRL secretion. These findings suggest that CRH-R1 mediates, at least in part, the restraint stress effects on the HPA, PRL, and reproductive axes.

ESTROGEN RESPONSE ELEMENT DEPENDENT AND INDEPENDENT ESTROGEN RECEPTOR ALPHA SIGNALING PATHWAYS DIFFERENTIALLY REGULATE PITUITARY GONADOTROPIN TRANSCRIPTION AND SECRETION IN THE FEMALE MOUSE

Pituitary gonadotropins luteinizing hormone (LH) and follicle stimulating hormone (FSH) are both secreted by pituitary gonadotropes in response to gonadotropin-releasing hormone (GnRH). However, these gonadotropins are independently regulated throughout the estrous cycle to coordinate the timing of follicle development and ovulation. GnRH release is suppressed by estrogen negative feedback until, on the afternoon of proestrous, when estrogen positive feedback actions result in a GnRH and LH surge and the induction of ovulation. Subsequently, a FSH surge occurs to stimulate the development of a new cohort of follicles until when inhibin, produced by follicles, feeds back to the pituitary to suppress further FSH production and release. In ovariectomized females, estrogen treatment is capable of suppressing LH and FSH. While known to require the estrogen receptor alpha (ERalpha), the molecular mechanisms of this suppression remain unclear. Classical ERalpha signaling occurs through binding to an estrogen response element (ERE) in DNA, whereas in nonclassical signaling, ERalpha participates in protein-protein interactions to alter the activity of transcription factors at non-ERE sites (i.e. NF-kB, AP-1, or Sp1). Previously, our lab generated a Nonclassical Estrogen Receptor Knock In (NERKI) mouse model using a mutant ERalpha that is unable to bind to ERE but retains EREindependent activity. Breeding the NERKI mouse with the ERalpha knock out model (ERKO), we are able to selectively restore only EREindependent signaling to the ERalpha null background (NERKI/ERKO) and genetically dissociate in vivo roles for the ERE-dependent and independent ERalpha signaling pathways. Using this model, we have recently shown the ERE-independent ERalpha signaling pathway as capable of mediating partial estrogen negative feedback of serum LH. In this study, the ERE-dependent and independent estrogen effects on serum FSH and pituitary gonadotropin LHbeta and FSHbeta subunit transcription are examined following ovariectomy. We find that estrogen mediated suppression of pituitary LHbeta mRNA and serum FSH require the EREdependent ERalpha pathway. In contrast, the ERE-independent ERalpha signaling pathway is capable of mediating partial estrogen suppression of FSHbeta mRNA transcription and serum LH. These results support a model where, in the absence of other ovarian factors, estrogen acting through the ERE-dependent ERalpha pathway suppresses both LH and FSH transcription and secretion, whereas estrogen acting through the ERE-independent pathway partially suppresses LH secretion and FSHbeta transcription but is permissive to LHbeta transcription and FSH secretion. These data suggest that the balance of ERE-dependent and independent ERalpha signaling pathways may enable estrogen to dynamically regulate the transcription and secretion of both pituitary gonadotropins LH and FSH across the estrous cycle. Supported by NIH/NICHD grant PO1 HD21921, CMBD Training Grant T32 GM008061, UVA Ligand Core- NICHD (SCCPRR) Grant U54-HD28934 (platform)

Differential regulation of the secretion of luteinizing hormone and follicle-stimulating hormone around the time of ovulation in the bitch

Plasma concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined 3–6 times daily in six Beagle bitches from the start of the follicular phase until 5 d after the estimated day of ovulation. The aim of the study was to gain more detailed information regarding the changes in and the temporal relation between these hormones around the time of ovulation. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. The mean duration of the pre-ovulatory FSH surge (110 ± 8 h) was significantly longer than that of the pre-ovulatory LH surge (36 ± 5 h). The FSH surge started concomitantly with the pre-ovulatory LH surge in four bitches, and 12 h before the start of the LH surge in the other two bitches. The pre-ovulatory LH surge had a bifurcated pattern in four bitches. The mean plasma LH concentration before (1.9 ± 0.4 μg/L) and after (1.9 ± 0.3 μg/L) the pre-ovulatory LH surge were similar. The mean plasma FSH concentration during the period 72–28 h before the pre-ovulatory LH surge (1.6 ± 0.3 U/L) was lower ( P < 0.001) than that during the period 100–144 h after the pre-ovulatory LH surge (3.1 ± 0.2 U/L). In conclusion, this study demonstrated concurrent pre-ovulatory surges of FSH and LH and provided more evidence for differential regulation of the secretion of FSH and LH.

Menstrual Cycle Characteristics and Predictability of Ovulation of Bhutia Women in Sikkim, India

Although a woman's menstrual history can have significant implications for health outcomes, few studies have examined menstrual cycle variability in non-western, non-clinically based populations. This study presents menstrual cycle characteristics from Bhutia women living in Gangtok, Sikkim, India. The Bhutia are one of two indigenous populations residing in this small, northeastern state of India. A total of 1067 cycles were recorded by 200 Bhutia women over the course of 12 months. Mean cycle length in this population was similar to reported mean cycle lengths for populations in the U.S (30 days vs. 28 days). Menstrual cycles in this sample were highly variable with most women experiencing more than one short or long menstrual cycle. The frequency of irregular menstrual cycles experienced by individuals also varied significantly by season. A body mass index (BMI) above or below the WHO defined normal range was associated with higher rates of irregular cycles. Leutenizing hormone (LH) and follicle stimulating hormone (FSH) levels were also determined from urine samples collected just before mid-cycle, based on median cycle lengths. Although menstrual cycles in this sample were highly variable, median cycle length was still useful in predicting timing of the pre-ovulatory hormone surges of LH and FSH. Frequency of irregular cycles did impact the successful capture of the LH and FSH peak values.

Temporal relations between plasma concentrations of luteinizing hormone, follicle-stimulating hormone, estradiol-17β, progesterone, prolactin, and α-melanocyte-stimulating hormone during the follicular, ovulatory, and early luteal phase in the bitch

Compared with other domestic animals, relatively little is known about the changes in, and temporal relations between, reproductive hormones around the time of ovulation in the domestic bitch. Therefore, plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol-17β, progesterone, prolactin (PRL), and α-melanocyte-stimulating hormone (α-MSH) were determined one to six times daily from the start of the follicular phase until 5 days after the estimated day of ovulation in six Beagle bitches. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. A pre-ovulatory PRL or α-MSH surge was not observed. The pre-ovulatory FSH and LH surges started concomitantly in four bitches, but in two bitches the FSH surge started 12 h earlier than the LH surge. The FSH surge (110 ± 8 h) lasted significantly longer than the LH surge (36 ± 5 h). In contrast with the pre-ovulatory FSH surge, the pre-ovulatory LH surge was bifurcated in four of six bitches. The mean plasma LH concentrations before (1.9 ± 0.4 μg/L) and after (1.9 ± 0.3 μg/L) the LH surge were similar, but the mean plasma FSH concentration before the FSH surge (1.6 ± 0.3 U/L) was significantly lower than that after the FSH surge (3.1 ± 0.2 U/L). In most bitches the highest plasma estradiol-17β concentration coincided with or followed the start of the pre-ovulatory LH surge. In five of the six bitches the plasma progesterone concentration started to rise just before or concurrently with the start of the LH surge. In conclusion, the results of this study provide evidence for the differential regulation of the secretion of LH and FSH in the bitch. In addition, the interrelationship of the plasma profiles of estradiol-17β and LH suggests a positive feedback effect of estradiol-17β on LH surge release. The start of the pre-ovulatory LH surge is associated with an increase in the plasma progesterone concentration in this species.

Follicle profile and plasma gonadotropin concentration in pubertal female ponies

Twelve female ponies were examined daily for 30 days and classified as ovulating (OV; N = 6; 197 +/- 6 kg) or prepubertal (PP; N = 6; 196 +/- 9 kg). Follicles were detected by ultrasound and gonadotropins quantified by radioimmunoassay. The mean diameter of the largest follicles was significantly larger in OV (38 +/- 1 mm) than in PP (26 +/- 2 mm) but there was no difference between groups in the size of the second largest follicle. There were more small follicles (<24 mm) in the PP than in the OV group, but PP fillies had a smaller number of follicles >29 mm than the OV fillies. Follicle-stimulating hormone (FSH) levels did not differ between groups but PP fillies had lower luteinizing hormone (LH) peak (8 +/- 1 ng/ml) and basal (4 +/- 0.5 ng/ml) levels, lower peak magnitude (2 +/- 0.2 ng/ml) and period average (5 +/- 0.6 ng/ml) than OV fillies (32 +/- 4.5, 8 +/- 1.2, 17.1 +/- 6, and 15 +/- 2.3 ng/ml, respectively). The PP group, in contrast to the OV group, showed no relationship between FSH surge and follicle wave emergence. We conclude that an LH concentration higher than 8 ng/ml is needed for follicle growth to a preovulatory size. Wave emergence and FSH secretion seem to be independent events, probably due to an inhibitory neural system in these PP animals. PP fillies may provide a physiological model for the study of follicle wave emergence which apparently does not depend on gonadotropin levels.

Estradiol benzoate delays new follicular wave emergence in a dose-dependent manner after ablation of the dominant ovarian follicle in cattle.

Administration of estradiol benzoate (EB) induces atresia of the dominant follicle (DF) in the ovaries of cattle within 36 h but emergence of a new wave of follicular development is delayed by 3-5 days. The present study investigated the role of EB in determining timing of emergence of a new follicular wave after removing the influence of the DF. At 6.4+/-0.2 days after ovulation in Angus and Angus/Simmental cattle (n=26), aged 4.9+/-0.6 years and weighing 634+/-20 kg, all ovarian follicles > or =5mm in diameter were aspirated with a 17-gauge needle using an ultrasound-guided transvaginal approach (Day 0 or Hour 0) and animals immediately received 0 (0EB), 1 (1EB), 2 (2EB) or 4 (4EB) mg EB i.m./500 kg body weight (n=6 or 7 per treatment). Ovarian structures were monitored by ultrasonography on a daily basis until emergence of a new wave of follicular development. Concentrations of estradiol (E2) were different among all treatments between Hours 24 and 72, increasing (P<0.01) with greater doses of EB administered. Hour of peak follicle-stimulating hormone (FSH) was 29.3+/-4.0, 53.3+/-4.5, 81.1+/-15.5, and 91.4+/-8.2 for the 0EB, 1EB, 2EB, and 4EB treatments, respectively, and emergence of a new wave of follicular development occurred on Days 1.5+/-0.2, 3.3+/-0.3, 4.0+/-0.6 and 4.4+/-0.4, respectively. Timing of peak FSH and emergence of a new wave of follicular development was earliest (P<0.05) in the 0EB treatment, similar (P>0.1) among the 1EB and 2EB treatments, and most delayed (P<0.05) in the 4EB treatment when compared to the 0EB or 1EB treatments. The overall mean interval from peak FSH to emergence of a new wave of follicular development was 15.7+/-3.3 h and was not affected by treatment. Concentrations of E2 at 24 h before new emergence were not different among EB-treated animals (20.2+/-5.5 pg/ml), but lower (P<0.01) in the 0EB treatment (1.6+/-0.2 pg/ml). In a dose-dependent manner, EB delayed the pre-emergence surge in FSH that stimulates new follicular development after the DF has ceased to be functional. The importance of using an 'optimal' dose of EB in hormonal regimens using this agent to strategically regulate follicular development is emphasized by the outcomes of this study.

Estrogen-Induced Gonadotropin Surge in Rhesus Monkeys Is Not Inhibited by Cortisol Synthesis Inhibition or Hypoglycemia

Acute administration of corticotrophin-releasing hormone (CRH) has been shown to inhibit gonadotropin secretion in several species including rodents, sheep, humans, and nonhuman primates. Similarly, a variety of acute stressors have been shown to inhibit tonic gonadotropin secretion and may do so through a CRH mechanism. Stress-induced inhibition of tonic gonadotropin secretion below levels required for follicular maturation would be expected to inhibit ovulation. An additional mechanism whereby acute stressors could interfere with ovulation is through inhibition of the preovulatory gonadotropin surge. In the present study, we determined the effect of acute activation of the hypothalamic-pituitary-adrenal (HPA) axis on phasic gonadotropin secretion in female rhesus monkeys. Activation of the HPA axis was achieved by either a hypoglycemic challenge or blockage of cortisol synthesis with metyrapone, 24 h after an estradiol benzoate challenge. Neither metyrapone nor insulin-induced hypoglycemia inhibited gonadotropin secretion. In fact, the initiation of the luteinizing hormone and follicle-stimulating hormone surge was advanced by 7.4 +/- 0.4 h (p < 0.001) and 4.8 +/- 1.4 h (p = 0.04) respectively, in metyrapone-treated monkeys compared with saline controls. By contrast, hypoglycemia did not affect the gonadotropin surge. The gonadotropin surge was preceded by increased progesterone secretion in metyrapone-treated but not insulin-treated monkeys. This difference in progesterone secretion likely explains the advancement of the gonadotropin surge in the metyrapone-treated animals.