Effects of hyperandrogenemia and increased adiposity on reproductive and metabolic parameters in young adult female monkeys

Many patients with hyperandrogenemia are overweight or obese, which exacerbates morbidities associated with polycystic ovary syndrome (PCOS). To examine the ability of testosterone (T) to generate PCOS-like symptoms, monkeys received T or cholesterol (control) implants (n = 6/group) beginning prepubertally. As previously reported, T-treated animals had increased neuroendocrine drive to the reproductive axis [increased luteinizing hormone (LH) pulse frequency] at 5 yr, without remarkable changes in ovarian or metabolic features. To examine the combined effects of T and obesity, at 5.5 yr (human equivalent age: 17 yr), monkeys were placed on a high-calorie, high-fat diet typical of Western cultures [Western style diet (WSD)], which increased body fat from <2% (pre-WSD) to 15-19% (14 mo WSD). By 6 mo on WSD, LH pulse frequency in the controls increased to that of T-treated animals, whereas LH pulse amplitude decreased in both groups and remained low. The numbers of antral follicles present during the early follicular phase increased in both groups on the WSD, but maximal follicular size decreased by 50%. During the late follicular phase, T-treated females had greater numbers of small antral follicles than controls. T-treated monkeys also had lower progesterone during the luteal phase of the menstrual cycle. Although fasting insulin did not vary between groups, T-treated animals had decreased insulin sensitivity after 1 yr on WSD. Thus, while WSD consumption alone led to some features characteristic of PCOS, T + WSD caused a more severe phenotype with regard to insulin insensitivity, increased numbers of antral follicles at midcycle, and decreased circulating luteal phase progesterone levels.

Evidence of GnRH antagonist escape in obese women

CONTEXT

Assisted reproductive technology (ART) cycle cancelation rates are increased among overweight and obese women; however, the reasons for this are not completely clear. Premature luteinization due to inadequate endogenous gonadotropin suppression is a possibility for this higher risk of cancellation.

OBJECTIVE

The objective of the study was to investigate the impact of female obesity on the pharmacokinetics of cetrorelix (GnRH antagonist).

DESIGN

This was an interventional study.

SETTING

The study was conducted at a university clinical and translational research center.

PARTICIPANTS

Regularly menstruating obese (n = 10) and normal-weight (n = 10) women participated in the study.

INTERVENTIONS

A frequent blood sampling study was performed after a GnRH antagonist was administered, followed by recombinant LH.

MAIN OUTCOMES MEASURED

Pharmacokinetics of cetrorelix in obese vs normal weight women were measured.

RESULTS

Five of the obese women (50%) and none of the normal-weight women had a rebound of LH (defined as >50% increase in LH level from nadir) over the 14-hour postdose observation period. The obese group had a significantly decreased distributional half-life of cetrorelix compared with the normal-weight group (8.1 ± 1.6 vs 12.7 ± 6.2 hours, P = .02). The obese group exhibited increased clearance of cetrorelix compared with the normal-weight group (25.8 ± 6.8 vs 20.1 ± 8.3 L/h, P = .058).

CONCLUSIONS

The altered pharmacokinetics of cetrorelix in obese women may lead to premature ovulation during ART, and this could be one of the mechanisms that results in increased cycle cancelation in this group of women. In accordance with the higher gonadotropin requirements for obese women undergoing ART, weight-based dosing of GnRH antagonists may be required.

Basal progesterone level as the main determinant of progesterone elevation on the day of hCG triggering in controlled ovarian stimulation cycles

PURPOSE

Modest increases of serum progesterone at human chorionic gonadotrophin (hCG) administration in controlled ovarian hyperstimulation (COH) cycles have been shown to have a negative impact on pregnancy outcomes. The aim of this study was to identify early predictors of progesterone elevation at hCG.

DESIGN

Pregnancy outcome of 303 consecutive patients undergoing COH and fresh day-3 embryo transfer was analysed. Considering the non-linear relationship between progesterone at hCG triggering and pregnancy outcomes, partial area under the curve (pAUC) analysis was used to implement marker identification potential of receiver operating characteristic (ROC) curve analysis. Multivariate logistic analysis was then performed to identify predictors of progesterone rise.

RESULTS

Pregnancy outcomes could be predicted by pAUC analysis (pAUC = 0.58, 95 % CI 0.51-0.66, p = 0.02) and a significant detrimental cut-off could be calculated (progesterone at hCG > 1.35 ng/ml). Total dose of rFSH administered, E2 level at hCG but mostly basal progesterone level (OR = 12.21, 95 % CI 1.82-81.70) were predictors of progesterone rise above the cut-off.

CONCLUSION

Basal progesterone is shown to be the main prognostic factor for progesterone elevation. This observation should be taken into consideration in the clinical management of IVF/ICSI cycles to improve pregnancy outcomes.

Familial male-limited precocious puberty in neurofibromatosis type I

Precocious puberty in patients with neurofibromatosis type 1 (NF-1) is predominantly central in origin, with intracranial pathologies like optic glioma. We describe one patient with NF-1 who presented with precocious puberty with the eventual diagnosis of familial male-limited precocious puberty and share the potential pitfalls. He presented at 7 years of age with growth spurt and pubertal genitalia development with enlarged testicular volume of 7 mL, but LHRH stimulation test revealed blunted luteinizing hormone and follicle-stimulating hormone peak suggestive of a peripheral cause, contrary to the expectation due to the background of NF-1. Testosterone level was elevated with bone age advancement by 2 years. Genetic analysis revealed a previously reported heterozygous missense mutation of the luteinizing hormone/choriogonadotropin receptor gene Ala572Val. His father was also heterozygous for the same mutation but was apparently asymptomatic and not short.

CONCLUSION

Our report illustrates two potential pitfalls in the clinical evaluation of patients with familial male-limited precocious puberty (FMPP). Firstly, patients with FMPP will have mild to moderately enlarged testes and should not be wrongly diagnosed as central precocious puberty without the gonadotropin-releasing hormone stimulation test. Secondly, family members with the same mutation may have different phenotypic severities, where some male carriers may have subtle features.

Metabolic syndrome induces inflammation and impairs gonadotropin-releasing hormone neurons in the preoptic area of the hypothalamus in rabbits

Rabbits with high fat diet (HFD)-induced metabolic syndrome (MetS) developed hypogonadotropic hypogonadism (HH) and showed a reduced gonadotropin-releasing hormone (GnRH) immunopositivity in the hypothalamus. This study investigated the relationship between MetS and hypothalamic alterations in HFD-rabbits. Gonadotropin levels decreased as a function of MetS severity, hypothalamic gene expression of glucose transporter 4 (GLUT4) and interleukin-6 (IL-6). HFD determined a low-grade inflammation in the hypothalamus, significantly inducing microglial activation, expression and immunopositivity of IL-6, as well as GLUT4 and reduced immunopositivity for KISS1 receptor, whose mRNA expression was negatively correlated to glucose intolerance. Correcting glucose metabolism with obetcholic acid improved hypothalamic alterations, reducing GLUT4 and IL-6 immunopositivity and significantly increasing GnRH mRNA, without, however, preventing HFD-related HH. No significant effects at the hypothalamic level were observed after systemic anti-inflammatory treatment (infliximab). Our results suggest that HFD-induced metabolic derangements negatively affect GnRH neuron function through an inflammatory injury at the hypothalamic level.

Identification of a novel kisspeptin with high gonadotrophin stimulatory activity in the dog

Kisspeptin (KISS1) and its receptor (KISS1r) are essential for normal reproductive function in many species, but the role of kiss1/kiss1r signalling in the dog has not yet been elucidated. The aims of this study were to identify the canine kiss1 and kiss1r genes and to determine gonadotrophin and oestradiol stimulatory activity of KP-10, the shortest biologically active form of KISS1. Canine kiss1 and kiss1r genes were localized by comparing the reference dog genome with relevant human cDNA sequences, using BLASTn software. The amino acid sequence of canine KP-10 (YNWN V FGLR Y ) differs at two positions from human KP-10 (YNWN S FGLR F ). A single bolus of canine KP-10 was administered intravenously to anoestrous Beagle bitches in dosages of 0, 0.1, 0.2, 0.3, 0.5, 1, 5, 10, and 30 μg/kg. Blood samples were collected before and after canine KP-10 administration for the measurement of plasma luteinizing hormone (LH, all doses), follicle-stimulating hormone (FSH) and oestradiol (1-30 μg/kg). From 0.2 μg/kg onwards, canine KP-10 resulted in a rapid and robust rise in plasma LH concentration (max. at 10 min). KP-10 also resulted in a rapid and robust rise in plasma FSH concentration (max. at 10-20 min). Plasma oestradiol concentration increased significantly after dosages of 1, 5, and 10 μg/kg and reached a maximum at 60-90 min. In conclusion, canine KP-10 is a potent kisspeptin which elicits robust gonadotrophin and oestradiol responses in anoestrous bitches, suggesting that canine kiss1/kiss1r are cogent targets for modulating reproduction in dogs.

An anti-steroidogenic inhibitory primer pheromone in male sea lamprey (Petromyzon marinus)

Reproductive functions can be modulated by both stimulatory and inhibitory primer pheromones released by conspecifics. Many stimulatory primer pheromones have been documented, but relatively few inhibitory primer pheromones have been reported in vertebrates. The sea lamprey male sex pheromone system presents an advantageous model to explore the stimulatory and inhibitory primer pheromone functions in vertebrates since several pheromone components have been identified. We hypothesized that a candidate sex pheromone component, 7α, 12α-dihydroxy-5α-cholan-3-one-24-oic acid (3 keto-allocholic acid or 3kACA), exerts priming effects through the hypothalamic-pituitary-gonadal (HPG) axis. To test this hypothesis, we measured the peptide concentrations and gene expressions of lamprey gonadotropin releasing hormones (lGnRH) and the HPG output in immature male sea lamprey exposed to waterborne 3kACA. Exposure to waterborne 3kACA altered neuronal activation markers such as jun and jun N-terminal kinase (JNK), and lGnRH mRNA levels in the brain. Waterborne 3kACA also increased lGnRH-III, but not lGnRH-I or -II, in the forebrain. In the plasma, 3kACA exposure decreased all three lGnRH peptide concentrations after 1h exposure. After 2h exposure, 3kACA increased lGnRH-I and -III, but decreased lGnRH-II peptide concentrations in the plasma. Plasma lGnRH peptide concentrations showed differential phasic patterns. Group housing condition appeared to increase the averaged plasma lGnRH levels in male sea lamprey compared to isolated males. Interestingly, 15α-hydroxyprogesterone (15α-P) concentrations decreased after prolonged 3kACA exposure (at least 24h). To our knowledge, this is the only known synthetic vertebrate pheromone component that inhibits steroidogenesis in males.

Disorders of childhood growth and development: precocious puberty

Precocious puberty is defined as pubertal development that begins at an earlier age than expected; most US pediatric endocrinology subspecialists use cutoff ages of 8 years for girls and 9 years for boys. Early activation and maturation of the hypothalamic-pituitary-gonadal axis leads to hormonal changes, physical signs of puberty, and acceleration of linear growth. Factors affecting puberty include race/ethnicity, obesity, and endocrine disruptors. The 2 forms of precocious puberty are central (gonadotropin-dependent precocious puberty) and peripheral (gonadotropin-independent precocious puberty). Most cases of the former have no identifiable etiology, whereas the latter is caused by increased secretion of sex hormones by the gonads or adrenal glands. It is important to differentiate progressive from nonprogressive precocious puberty to avoid unnecessary treatment for the latter; if diagnosis is uncertain, the child should be reassessed within several months. Evaluation begins with a detailed history and physical examination followed by an x-ray for bone age; in precocious puberty, bone age is greater than chronologic age. If indicated, additional serum testing (basal luteinizing hormone) and imaging studies should be obtained. Patients should be referred to a pediatric endocrinology subspecialist for treatment. It is essential to manage underlying etiologies. Gonadotropin-releasing hormone agonists should be considered only for children with progressive central precocious puberty to prevent short stature. For children with apparent nonprogressive precocious puberty, follow-up every 3 to 6 months between ages 6 and 7 years is recommended to assess for progression.

Gonadotrophin-releasing hormone release into the hypophyseal portal blood of the ewe mirrors both pulsatile and continuous intravenous infusion of kisspeptin: an insight into kisspeptin's mechanism of action

Recent studies have demonstrated that kisspeptin (Kp) administration, given as a slow constant infusion of Kp10 (the shortest endogenous form of the Kp molecules which carries biological activity), is able to stimulate gonadotrophin secretion and induce ovulation in anoestrus acyclic ewes. Detailed analysis of peripheral luteinising hormone (LH) concentrations, obtained at 10-min intervals, suggested that this Kp10 treatment induced the continuous release of gonadotrophins. Whether this apparent constant secretion of LH resulted from a continuous elevation of GnRH or discrete high-frequency pulses could not be determined. In the present study, we monitored the patterns of gonadotrophin-releasing homrone (GnRH) secreted into hypophyseal portal blood (HPB) and LH in the peripheral circulation when Kp10 was administered either as discrete pulses or by means of a continuous infusion. Samples of HPB and peripheral blood were obtained at 2 and 10-min intervals, respectively, over a 6-h period, from anoestrous acyclic ewes that received an i.v. bolus injection of Kp10 at 1 h and an infusion of Kp10 between hours 2 and 6. GnRH release following Kp10 administration appeared to be dose-dependent, with larger responses being seen to the 20 μg bolus and 20 μg/h infusion than to the 10 μg bolus and 10 μg/h infusion, with the latter being marginally effective in inducing LH release. Bolus injections of Kp10 (either 20 or 10 μg) induced a sharp GnRH pulse in HPB and a discrete LH pulse in peripheral blood. By contrast, constant infusion of Kp10 (either 20 or 10 μg/h for 4 h) induced a sustained increase in baseline GnRH secretion with no convincing evidence of strictly episodic release. Values remained continuously elevated in HPB. No sign of pituitary desensitisation was observed at either concentration. Finally, i.v. injection of a large bolus (500 μg) of Kp10 produced immediate pharmacological concentrations of Kp10 in the peripheral circulation but were not associated with detectable levels of the peptide in the cerebrospinal fluid. In summary, our results demonstrate that the mode of Kp10 administration (pulsatile versus continuous) is important in shaping the pattern of GnRH secretion and suggests that this regulatory effect is most likely exerted at the level of the terminals of GnRH neurones. Moreover our data also suggest that Kp is involved in, rather than having a permissive role in, the control of endogenous GnRH pulsatility.

The decline in pulsatile GnRH release, as reflected by circulating LH concentrations, during the infant-juvenile transition in the agonadal male rhesus monkey (Macaca mulatta) is associated with a reduction in kisspeptin content of KNDy neurons of the arcuate nucleus in the hypothalamus

Puberty in primates is timed by 2 hypothalamic events: during late infancy a decline in pulsatile GnRH release occurs, leading to a hypogonadotropic state that maintains quiescence of the prepubertal gonad; and in late juvenile development, pulsatile GnRH release is reactivated and puberty initiated, a phase of development that is dependent on kisspeptin signaling. In the present study, we determined whether the arrest of GnRH pulsatility in infancy was associated with a change in kisspeptin expression in the mediobasal hypothalamus (MBH). Kisspeptin was determined using immunohistochemistry in coronal hypothalamic sections from agonadal male rhesus monkeys during early infancy when GnRH release as reflected by circulating LH concentrations was robust and compared with that in juveniles in which GnRH pulsatility was arrested. The distribution of immunopositive kisspeptin neurons in the arcuate nucleus of the MBH of infants was similar to that previously reported for adults. Kisspeptin cell body number was greater in infants compared with juveniles, and at the middle to posterior level of the arcuate nucleus, this developmental difference was statistically significant. Neurokinin B in the MBH exhibited a similar distribution to that of kisspeptin and was colocalized with kisspeptin in approximately 60% of kisspeptin perikarya at both developmental stages. Intensity of GnRH fiber staining in the median eminence was robust at both stages. These findings indicate that the switch that shuts off pulsatile GnRH release during infancy and that guarantees the subsequent quiescence of the prepubertal gonad involves a reduction in a stimulatory kisspeptin tone to the GnRH neuronal network.

Age-related changes in gonadal and serotonergic axes of broiler breeder roosters

Fertility of domestic roosters decreases at ≈ 50 wk of age. In a previous study on aging white leghorn roosters, low fertility was accompanied by low levels of both hypothalamic vasoactive intestinal peptide (VIP) and pituitary prolactin (PRL) mRNA expression; however, their role in aging broiler breeder rooster reproduction is still unclear. In this study we compared reproductive activities of young (35-wk-old) and aging (73-wk-old) broiler breeder roosters. Weekly semen volume; concentration and ejaculation grade; and concentrations of plasma testosterone, estradiol, and PRL were examined. Every other week, 10 roosters from each group were euthanized, their testes weighed, and hypothalamus and pituitary removed to determine mRNA expression of hypothalamic GnRH-I, pituitary FSH, pituitary LH, hypothalamic VIP, and pituitary PRL. Aging roosters had significantly lower testis weight and semen volume, sperm concentration, ejaculation grade and plasma testosterone and low hypothalamic GnRH-I, pituitary FSH, and pituitary LH mRNA expression than young roosters (P ≤ 0.05). Aging roosters had higher concentrations of plasma estradiol and PRL and higher hypothalamic VIP and pituitary PRL mRNA expression than young roosters (P ≤ 0.05). We suggest that PRL, which is known to inhibit the gonadal axis, and its releasing factor, VIP, play an important role in the reproductive failure associated with age in broiler breeder roosters.

An Evaluation of the Pharmacokinetics and Pharmacodynamics of the Histrelin Implant for the Palliative Treatment of Prostate Cancer

Seventeen patients with advanced prostate cancer were studied to evaluate the pharmacokinetics and pharmacodynamics of a hydrogel implant designed to deliver histrelin at a constant rate (50 microg/d) for 1 year. Serum histrelin levels were collected during the 52-week implantation period and after a second implant. Testosterone suppression was the primary pharmacodynamic endpoint, with treatment success defined as serum testosterone less than 50 ng/dL. The histrelin subdermal implant delivered constant histrelin levels, with mean serum histrelin of approximately 0.265 ng/mL over 52 weeks. At the end of 52 weeks, mean histrelin concentrations were 0.128 +/- 0.0652 ng/mL. Patients achieved chemical castration (testosterone less than 50 ng/mL) by week 4. In patients who had the first implant removed and received a new implant at the end of the first 52 weeks, testosterone suppression was not interrupted. The hydrogel implant provided consistent delivery of histrelin over 1 year and effectively suppressed testosterone in men with prostate cancer.

Kisspeptin signaling is required for the luteinizing hormone response in anestrous ewes following the introduction of males

The introduction of a novel male stimulates the hypothalamic-pituitary-gonadal axis of female sheep during seasonal anestrus, leading to the resumption of follicle maturation and ovulation. How this pheromone cue activates pulsatile secretion of gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) is unknown. We hypothesised that pheromones activate kisspeptin neurons, the product of which is critical for the stimulation of GnRH neurons and fertility. During the non-breeding season, female sheep were exposed to novel males and blood samples collected for analysis of plasma LH profiles. Females without exposure to males served as controls. In addition, one hour before male exposure, a kisspeptin antagonist (P-271) or vehicle was infused into the lateral ventricle and continued for the entire period of male exposure. Introduction of a male led to elevated mean LH levels, due to increased LH pulse amplitude and pulse frequency in females, when compared to females not exposed to a male. Infusion of P-271 abolished this effect of male exposure. Brains were collected after the male effect stimulus and we observed an increase in the percentage of kisspeptin neurons co-expressing Fos, by immunohistochemistry. In addition, the per-cell expression of Kiss1 mRNA was increased in the rostral and mid (but not the caudal) arcuate nucleus (ARC) after male exposure in both aCSF and P-271 treated ewes, but the per-cell content of neurokinin B mRNA was decreased. There was also a generalized increase in Fos positive cells in the rostral and mid ARC as well as the ventromedial hypothalamus of females exposed to males. We conclude that introduction of male sheep to seasonally anestrous female sheep activates kisspeptin neurons and other cells in the hypothalamus, leading to increased GnRH/LH secretion.

[The influence of high fluoride exposure in drinking water on endocrine hormone in female]

OBJECTIVE

To explore the influence of water fluoride exposure on reproductive hormones in female.

METHODS

Cross-sectional study was conducted in seven villages of a county in Henan province by using simple random sampling including high fluoride area, defluoridation project area and control area on April, 2011 based on the preliminary study results of fluoride concentration in drinking water. Women who were born and growth or lived in the village at least 5 years and aged 18-48 years old were recruited using cluster sampling. They were divided into high fluoride group (HFG, 116 subjects), defluoridation project group (DFPG, 132 subjects) and control group (CG, 227 subjects) in accordance with the above areas. All subjects accepted questionnaire and physical checkup. Fasting blood and morning urine samples were collected. The concentration of fluoride in urine was determined by fluoride ion selective electrode method. The serum level of GnRH was detected using enzyme linked immunosorbent assay (ELISA). The serum level of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T), estradiol (E2) were determined by chemiluminesence immunoassay (CLIA).

RESULTS

The average age was (39.44 ± 7.34), (38.84 ± 8.03), (37.45 ± 7.70) years old in female from DFPG, HFG and CG respectively, there were no significant differences among the three groups (F = 3.02, P = 0.05). The urine fluoride levels were (1.34 ± 1.07), (2.59 ± 1.57), (0.92 ± 0.46) mg/ml in female from DFPG, HFG and CG respectively, there was a significant difference among three groups (F = 105.38, P < 0.01). No significant differences were observed of serum GnRH, LH, T, FSH and E2 among three groups in follicular phase (P > 0.05). The serum levels of E2 in Ovulatory period were 67.73, 58.09, 84.96 pg/ml in female from DFPG, HFG and CG respectively. It was lower in HFG than that in CG (H = 4.00, P < 0.05). The serum levels of T in Ovulatory period were 0.55, 0.45, 0.55 ng/ml in female from DFPG, HFG and CG respectively. It was lower in HFG than that in DFPG (H = 6.47, P < 0.05), but no significant difference was observed between HFG and CG (H = 2.41, P > 0.05). The serum levels of GnRH in Luteal phase were 24.09, 20.16, 23.50 ng/ml in female from DFPG, HFG and CG respectively. It was lower in HFG than that in DFPG (H = 14.14, P < 0.05) and CG (H = 12.53, P < 0.05). The serum level of E2 in luteal phase were 81.47, 64.60, 74.55 pg/ml in female from DFPG, HFG and CG respectively. It was lower in HFG than that in DFPG (H = 5.69, P < 0.05). As for LH, FSH and T, no significant differences were observed among the three groups (P > 0.05 respectively). The abnormal rates of E2 level were 22.73 (30/102), 37.93 (44/72), 20.26 (46/181) in female from DFPG, HFG and CG respectively. The E2 abnormal rate in female from HFG was higher that from DFPG (χ(2) = 6.82, P < 0.05) and CG (χ(2) = 12.38, P < 0.05).

CONCLUSION

Fluoride exposure may influence reproductive hormones in female, especially in ovulatory and luteal phase of menstrual cycle.

Utility of Basal luteinizing hormone levels for detecting central precocious puberty in girls

The hallmark of puberty is the progressive increase in gonadotropin-releasing hormone (GnRH) activity, reflected by an increase in the circulating concentration of luteinizing hormone (LH). The GnRH stimulation test is widely used in the evaluation of precocious puberty. The aim of our study was to assess the diagnostic utility of basal LH for the diagnosis of central precocious puberty (CPP) in girls. A total of 803 girls were referred to Ajou University Hospital for evaluation of precocious puberty between 2008 and 2011. All subjects underwent GnRH-stimulation tests as part of their evaluation. Serum LH and follicle stimulating hormone (FSH) were measured by immunoradiometric assay before and after the GnRH injection. Of the 803 subjects, 505 (62.9%) were included in the pubertal response group and 298 (37.1%) were in the prepubertal response group. Basal LH level was identified as a significant predictor for CPP. Based on the ROC curve, the optimal cut off point of basal LH related to 'pubertal response' was 1.1 IU/l, which was associated with 69.1% sensitivity and 50.5% specificity, with an area under the ROC curve of 0.620 (95% CI, 0.581-0.660). It is concluded that a single basal LH measurement can be used as a screening test to identify girls with CPP and to determine who should undergo GnRH stimulation test.

Neuroendocrine control of FSH secretion: IV. Hypothalamic control of pituitary FSH-regulatory proteins and their relationship to changes in FSH synthesis and secretion

The current dogma is that the differential regulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) synthesis and secretion is modulated by gonadotropin-releasing hormone (GnRH) pulse frequency and by changes in inhibins, activins, and follistatins both at the pituitary and at the peripheral level. To date no studies have looked at the overlapping function of these regulators in a combined setting. We tested the hypothesis that changes in GnRH pulse frequency alter the relative abundance of these regulators at the pituitary and peripheral levels in a manner consistent with changes in pituitary and circulating concentrations of FSH; that is, an increase in FSH will be accompanied by increased stimulatory input (activin) and/or reduced follistatin and inhibin. Ovariectomized ewes were subjected to a combination hypothalamic pituitary disconnection (HPD)-hypophyseal portal blood collection procedure. Hypophyseal portal and jugular blood samples were collected for a 6-h period from non-HPD ewes, HPD ewes, or HPD ewes administered GnRH hourly or every 3 h for 4 days. In the absence of endogenous hypothalamic and ovarian hormones that regulate gonadotropin secretion, 3-hourly pulses of GnRH increased pituitary content of FSH more than hourly GnRH, although these differences were not evident in the peripheral circulation. The results failed to support the hypothesis in that the preferential increase of pituitary content of FSH by the lower GnRH pulse frequency could be explained by changes in the pituitary content of inhibin A, follistatin, or activin B. Perhaps the effects of GnRH pulse frequency on FSH is due to changes in the balance of free versus bound amounts of these FSH regulatory proteins or to the involvement of other regulators not monitored in this study.

Up to the challenge? Hormonal and behavioral responses of free-ranging male Cassin's sparrows, Peucaea cassinii, to conspecific song playback

The Challenge Hypothesis postulates that male vertebrates can respond to social challenges, such as simulated territorial intrusions, by rapidly increasing their concentrations of plasma androgens, such as testosterone (T). This increase may facilitate the expression of aggressive behavior and lead to persistence of this behavior even after withdrawal of the challenge, thus potentially promoting territoriality and the probability of winning future challenges. The scope of the Challenge Hypothesis was tested by exposing free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback (SPB) at the beginning of the vernal nesting season. Exposure to SPB stimulated aggressive behavior but did not influence plasma T. Furthermore, plasma T did not correlate with the duration of exposure to SPB, and the behavioral response to SPB did not differ in males that were challenged a second time shortly after the first challenge. As birds were investigated at a stage of their reproductive cycle when plasma T is presumably seasonally high due to photostimulation, the lack of hormonal response to SPB may have been due to the hypothalamus-pituitary-gonadal axis secreting hormones at maximum rates. This was not the case, however, because administration of gonadotropin-releasing hormone I rapidly stimulated the secretion of luteinizing hormone (LH) and T, and treatment with ovine LH rapidly stimulated T secretion.

Neuroendocrinology and ovarian aging

The ovarian aging, a dynamic process that precedes the clinical manifestations of menopause, can be assessed using ovarian reserve biomarkers. It is well-known that reproduction during the later years of reproductive life has known limitations that challenge the success of assisted reproduction. Therefore, a review of the neuroendocrine modifications during this critical period of reproductive life may help to elucidate the ovarian aging process and its impact on reproduction. In this review, we aim to further the discussion of neuroendocrine changes taking place during the ovarian aging process that may impact reproductive function.

Developmental changes in GnRH release in response to kisspeptin agonist and antagonist in female rhesus monkeys (Macaca mulatta): implication for the mechanism of puberty

Kisspeptin (KP) and KP-1 receptor (KISS1R) have emerged as important upstream regulators in the control of puberty. However, how developmental changes in KP-KISS1R contribute to the pubertal increase in GnRH release still remains elusive. In this study, we examined the effects of the KP agonist, human KP-10 (hKP-10), and the KP antagonist, peptide 234, on in vivo GnRH release in prepubertal and pubertal ovarian-intact female rhesus monkeys using a microdialysis method. We found that direct infusion of hKP-10 into the medial basal hypothalamus and stalk-median eminence region stimulated GnRH release in a dose-responsive manner, whereas infusion of peptide 234 suppressed GnRH release in both developmental stages. Because ovarian steroid feedback on GnRH release becomes prominent after the initiation of puberty in primates, we further examined whether ovarian steroids modify the GnRH response to hKP-10. Results demonstrate that the hKP-10-induced stimulation of GnRH release was eliminated by ovariectomy in pubertal, but not prepubertal, monkeys. Furthermore, replacement of estradiol into ovariectomized pubertal monkeys resulted in a partial recovery of the hKP-10-induced GnRH release. Collectively, these results suggest that a KISS1R-mediated mechanism, in addition to the pubertal increase in KP-54 release we previously reported, contributes to the pubertal increase in GnRH release and that there is a switch from an ovarian steroid-independent to -dependent mechanism in the response of GnRH to KP.

Seasonal variation in the gonadotropin-releasing hormone response to kisspeptin in sheep: possible kisspeptin regulation of the kisspeptin receptor

Kisspeptin signaling in the hypothalamus appears critical for the onset of puberty and driving the reproductive axis. In sheep, reproduction is seasonal, being activated by short days and inhibited by long days. During the non-breeding (anestrous) season, gonadotropin-releasing hormone (GnRH) and gonadotropin secretion is reduced, as is the expression of Kiss1 mRNA in the brain. Conversely, the luteinizing hormone response to kisspeptin during this time is greater. To determine whether the GnRH response to kisspeptin is increased during anestrus, we utilized hypophysial portal blood sampling. In anestrus ewes, the GnRH and LH responses to kisspeptin were greater compared to the breeding season (luteal phase). To ascertain whether this difference reflects a change in Kiss1r, we measured its expression on GnRH neurons using in situ hybridization. The level of Kiss1r was greater during the non-breeding season compared to the breeding season. To further examine the mechanism underlying this change in Kiss1r, we examined Kiss1r/GnRH expression in ovariectomized ewes (controlling for sex steroids) during the breeding and non-breeding seasons, and also ovariectomized non-breeding season ewes with or without estradiol replacement. In both experiments, Kiss1r expression on GnRH neurons was unchanged. Finally, we examined the effect of kisspeptin treatment on Kiss1r. Kiss1r expression on GnRH neurons was reduced by kisspeptin infusion. These studies indicate the kisspeptin response is indeed greater during the non-breeding season and this may be due in part to increased Kiss1r expression on GnRH neurons. We also show that kisspeptin may regulate the expression of its own receptor.

The evaluation of estradiol and leptin action on the activity of the somatotropic and gonadotropic axes in peripubertal female rats

OBJECTIVE

Available data suggest that estrogens and leptin play a role in the control of the pubertal process. In humans and some mammal species the increase of the activity of gonadotropic axis accompanies the decrease in the rate of growth at puberty. The effect of 17β-estradiol and/or leptin administration on the somatotropic and gonadotropic axes was studied using prepubertal female rats as an animal model.

MATERIAL AND METHODS

Prepubertal female rats received estradiol/saline, estradiol/leptin, oil/leptin or oil/saline (vehicles) respectively. The changes of growth rate, and serum 17β-estradiol, leptin, GH, IGF-I and gonadotropins levels as well as LHRH and estrogen receptor (ER) concentrations in the medial basal hypothalamus (MBH) and the pituitary were determined. All hormones concentrations were measured by radioimmunoassay and ER by radioligand methods .

RESULTS

In estradiol and/or leptin treated animals noticeable reduction of rate of growth was found. The decrease of growth in response to estradiol treatment accompanied the increase GH level and the decrease of IGF-I concentration in the circulation. Both hormones operating together activated reproductive axis, what was manifested by a significant increase of LHRH abundant in the hypothalamus as well as elevated LH and FSH levels in the circulation. In these rats a significant decrease of the estrogen receptor concentrations in the pituitary was observed.

CONCLUSION

The role of estradiol and leptin in the control of growth and reproduction seems to overlap only partially. Estradiol plays a significant role in the activation of the reproductive axis, and leptin takes part as a permissive factor in pubertal process.

Neonatal gonadotropin therapy in male congenital hypogonadotropic hypogonadism

Congenital hypogonadotropic hypogonadism (CHH) causes pubertal failure and infertility in both women and men due to partial or total secretory failure of the two pituitary gonadotropins lutropin (LH) and follitropin (FSH) during periods of physiological activation of the gonadotropic axis. Men and women with CHH frequently seek treatment for infertility after hypogonadism therapy. Some etiologies, such as autosomal dominant or X-linked Kallmann syndrome, raise the question of hereditary transmission, leading to increasing demands for genetic counseling and monitoring of medically assisted pregnancies. Diagnosis and treatment of newborn boys is, therefore, becoming an increasingly important issue. In male individuals with complete forms of CHH, the antenatal and neonatal gonadotropin deficit leads to formation of a micropenis and cryptorchidism, which could undermine future sexual and reproductive functions. Standard treatments, usually started after the age of puberty, often only partially correct the genital abnormalities and spermatogenesis. The aim of this Review is to examine the possible additional benefits of neonatal gonadotropin therapy in male patients with CHH. Encouraging results of neonatal therapy, together with a few reports of prepubertal treatment, support the use of this novel therapeutic strategy aimed at improving sexual and reproductive functions in adulthood.

Gonadotropin-releasing hormone neurons extend complex highly branched dendritic trees outside the blood-brain barrier

GnRH neurons project axons to the median eminence to control pituitary release of gonadotropins and, as such, represent the principal output neurons of the neuronal network controlling fertility. It is well established that the GnRH neurons exhibit a simple bipolar morphology with one or two long dendrites. Using adult GnRH-green fluorescent protein transgenic mice and juxtacellular cell filling, we report here that a subpopulation of GnRH neurons located in the rostral preoptic area exhibit extremely complex branching dendritic trees that fill the organum vasculosum of the lamina terminalis (OVLT). The dendritic nature of these processes was demonstrated at both light and electron microscopic levels by the presence of spines, dendritic ultrastructure, and synapses. Further, electrophysiological recordings showed that GnRH neurons were excited by glutamate as well as kisspeptin puffed onto their dendrites located within the OVLT. Using iv injection of horseradish peroxidase, a molecule unable to penetrate the blood-brain barrier (BBB), we show that GnRH neuron cell bodies and dendrites within 100 μm of the OVLT reside outside the BBB. Approximately 85% of GnRH neurons in this area express c-Fos at the time of the GnRH surge. These observations demonstrate that GnRH neurons extend complex, highly branched dendritic trees beyond the BBB into the OVLT, where they will be able to sense directly molecules circulating in the bloodstream. This indicates a new mechanism for the modulation of GnRH neurons that extends considerably the range of factors that are integrated by these neurons for the control of fertility.

Developmental changes in hypothalamic Kiss1 expression during activation of the pulsatile release of luteinising hormone in maturing ewe lambs

Onset of puberty is characterised by a marked increase in the frequency of release of gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH). The Kiss1 gene plays a critical role in pubertal development, and its product, kisspeptin, stimulates GnRH and LH release. In the present study, we tested the hypothesis that Kiss1 gene expression in the preoptic area (POA) and hypothalamus increases during maturation of the reproductive neuroendocrine axis in association with increased LH pulsatility. Ovariectomised, oestradiol-replaced lambs were euthanised at 25, 30 and 35 weeks of age. Blood samples were collected before euthanasia to characterise the pattern of LH release. Kiss1 mRNA was detected in coronal sections of the POA and hypothalamus and Kiss1-expressing cells were identified on the basis of silver grain density. The mean number of Kiss1-expressing cells in the POA/periventricular (PeV) areas increased from 25 to 30 weeks of age. No further increase at 35 weeks of age was observed, and the changes in Kiss1 expression in the POA/PeV were independent of changes in LH pulse frequency. The mean number of Kiss1-expressing cells in the arcuate (ARC) nucleus did not differ among age groups, although it was greater in the middle ARC of lambs exhibiting increased frequency of LH release. The density of silver grains per cell did not differ among groups in any of the areas studied. The results obtained indicate that the Kiss1 gene is activated in the POA/PeV and ARC of ewe lambs during juvenile development, and that kisspeptin neurones in the middle ARC, in particular, are involved in the acceleration of pulsatile LH release during maturation of the reproductive neuroendocrine axis in ewe lambs.