LH Amplitude Research Articles

Exposure of rams in sexual rest to sexually activated males in spring increases plasma LH and testosterone concentrations

Eight stimulating rams, and twelve stimulated rams, were used to determine whether a similar endocrine response to the introduction of sexually active males in spring in a flock of ewes is observed in a flock of rams. The stimulating rams (n = 4) were induced into a sexually active state by exposure to 2 months of long days (16 h light/d) (15 December-15 February). At the end of the long-day period, rams were returned to the natural photoperiod. Control-stimulating rams (n = 4) were kept under the natural photoperiod. On April 20, stimulated rams were divided into 2 groups, and joined with activated (ACT; n = 6) or control stimulating rams (C; n = 6). On the day of ram introduction, stimulated rams were blood sampled for 8 h at 20-min intervals, from 4 h before to 4 h after ram introduction, and next day from 24 to 28 h after ram introduction, and analyzed for plasma LH concentrations, and 10, 20 and 30 days after ram introduction to measure plasma testosterone levels. Mean (±SEM) plasma LH concentrations (ng/ml) of stimulated rams were similar during the 4 h before stimulating-ram introduction (ACT: 0.59 ± 0.03; C: 0.53 ± 0.04; P > 0.05). The introduction of the photoperiod-treated stimulating rams increased LH concentrations of stimulated rams during the 4 h after their introduction (1.14 ± 0.37) compared with the C group (0.51 ± 0.03; P < 0.05), especially during the first hour (ACT: 0.93 ± 0.16; C: 0.49 ± 0.03; P < 0.05), and during the blood sampling period 24–28 h after ram introduction (0.75 ± 0.07 vs. 0.58 ± 0.04; P < 0.05). Before the introduction of stimulating rams, the LH pulse frequencies and amplitudes did not differ between groups; however, LH pulsatility was higher at 4 h (0.58 ± 0.11 pulses/h; P < 0.05), and had trend to be higher 24 h (0.50 ± 0.06) (P = 0.10) after the introduction of the photoperiod-treated stimulating rams compared with the control-stimulating rams (0.29 ± 0.08 and 0.29 ± 0.10, respectively). As for LH pulses, there was an effect of group (P < 0.05) on LH amplitude, which presented a trend to be higher in ACT rams 4 h after ram introduction (1.68 ± 0.30; P < 0.10) and higher 24 h (1.07 ± 0.08; P < 0.05) after ram introduction, compared with LH amplitudes of C rams (0.71 ± 0.06 and 0.82 ± 0.07, respectively). Plasma testosterone concentrations of rams exposed to photoperiod-treated activated rams were higher than those of rams exposed to control-stimulating rams, at 4 h, 20 and 30 days after ram introduction (P < 0.05). In conclusion, sexually active rams in spring are able to stimulate LH and testosterone secretion of other rams in sexual rest, a phenomenon we called “ram-to-ram effect".

PSXII-16 High and medium ADG on LH profile in early-weaned heifers

Abstract This study evaluated the effects of ADG on number of pulses, amplitude and concentration of LH in pre-pubertal early-weaned heifers. Twenty ½Angus x ½Nellore were weaned (86±3 d of age and 91±1 kg BW), and allocated in 2×2 factorial design. Heifers were submitted to high (H) and medium (M) ADG in two periods. The first period occurred from 3 to 7 mo and the second from 7 mo to puberty (HH, HM, MH and MM). Diets in the first (CP 19%, NDF 24% and TDN 79%) and second periods (CP 14%, NDF 24% and TDN 78 %) were the same for all treatments, but the amount was controlled to get the ADG. Weekly, heifers were weighed and puberty status assessed by US. Serial blood samples were collected every 15 min for 12h at 6.5, 9.5 and 11.5 mo of age. The data were evaluated using SAS. The ADG was higher in H than M group in the first period (0.99±0.06 kg vs. 0.51±0.04 kg). In the second period, the ADG was 0.81±0.03 (HH), 0.5±0.03 (HM), 1.0±0.04 (MH) and 0.68±0.03 (MM). At 6.5 mo of age, heifers in H had an increase in LH pulses (2.1±0.5) compared with M (0.7±0.5) (period x age interaction P = 0.04). There was no effect of treatments on LH pulses in other ages, and in amplitude of LH pulse. The LH concentration was higher in HH than HM, MH and MM at 9.5 mo (1.72 vs. 1.07, 1.46 and 1.25±0.2 ng/mL) and 11.5 mo of age (2.01 vs. 1.65, 1.48 and 1.53±0.2 ng/mL), respectively. Despite differences in LH patterns, HH heifers reached puberty at a similar age to HM and MH (12±0.2 mo), however MM heifers (14.4±0.4 mo) reached puberty later (P = 0.09). Increasing ADG on juvenile period increased LH pulses but did not induce precocious puberty.

OR33-4 A Single Subcutaneous Injection Of The Kisspeptin Analogue, MVT-602, Induces A More Prolonged LH Surge Compared With Kisspeptin-54 In Healthy Women

Background Kisspeptin is a hypothalamic neuropeptide that is requisite for normal reproductive health. A subcutaneous bolus of the native form of kisspeptin (kisspeptin-54; KP54) induces an LH-surge lasting 12-14hrs, to safely mature oocytes during in vitro fertilisation (IVF) treatment. The kisspeptin analogue, MVT-602, has a longer half-life (t1/2 1.5-2.2h) than native KP54 (t1/2 0.5h), which could therefore confer significant advantages as an oocyte maturation trigger in the treatment of infertility. Whilst MVT-602 has been shown to stimulate LH release in men, its effects in women have not previously been investigated. To address this, we studied the effect of MVT-602 on gonadotrophin release in healthy women for the first time. Methods A two-phase dose-finding study was undertaken during the early follicular phase (Day 1-4) of 12 healthy women aged 18-35yrs with regular menstrual cycles. During phase 1, a broad dose-range for MVT-602 was determined: three women received a single subcutaneous bolus of one of five doses of MVT-602 (0.003, 0.03, 0.1, 0.3, or 1.0nmol/kg) in successive menstrual cycles. Reproductive hormones were measured every 30min for 14hrs post-MVT-602, and again at 24hrs and 48hrs post-injection. During phase 2, an additional 9 women received either KP54 (9.6nmol/kg), or MVT-602 at doses of 0.01 or 0.03nmol/kg during the follicular phase of successive menstrual cycles, following which reproductive hormone levels were monitored every 30mins for 24hrs post-injection. Intervention groups were compared by one-way ANOVA with post hoc Tukey’s test. ResultsPhase 1: Peak serum LH levels occurred between 14-24hrs and no further increases occurred with MVT-602 at doses greater than 0.03 nmol/kg. Phase 2: Peak amplitude of serum LH was found to be similar following KP54 and MVT-602 (mean±SD of peak LH KP54 12.3 ±5.3iU/L; MVT-602 0.01nmol/kg 11.4 ±4.2iU/L; MVT-602 0.03nmol/kg 11.1 ±3.0iU/L, p>0.05). However, time to peak LH was later following MVT-602 (22hrs) when compared with KP54 (4.9hrs; P<0.0001). Thus, the area under the curve (AUC) for LH exposure was significantly increased following MVT-602 when compared with KP54 (mean±SD of AUC LH KP54 9,095 ±5,632iU.min/L; MVT-602 0.01nmol/kg 18,129 ±6,471iU.min/L, P=0.02 vs KP54; MVT-602 0.03nmol/kg 20,086 ±6,227iU.min/L, P=0.004 vs KP54). Conclusion A single subcutaneous bolus of MVT-602 in healthy women resulted in an LH surge of similar amplitude, but of longer duration than by KP54. During studies evaluating the utility of KP54 as a trigger of oocyte maturation in IVF treatment, extending the duration of LH surge with a second bolus of KP54 safely optimised oocyte maturation. Thus, the prolonged gonadotrophin surge induced by MVT-602 could be of significant utility not only to safely optimise oocyte maturation in IVF treatment, but also to treat other reproductive disorders affecting women’s health.

OR15-4 Long-Term Follow-Up of a Female with a Mutation in the Estrogen Receptor Alpha (ESR1) Gene

We previously reported the first female with a mutation in the ESR1 gene encoding estrogen receptor-α (ER-α), which dramatically reduced estrogen signaling in vitro. She presented at 179/12 years with absent breast development, markedly elevated serum estradiol and estrone levels, modestly high gonadotropins, and multicystic ovaries by ultrasound. The natural history of estrogen insensitivity in women is unknown. The purpose of this report is to present: 1) the neuroendocrine phenotype; 2) studies to identify a ligand to stimulate the mutant receptor; and 3) the effect of targeted treatment. We now provide long-term clinical follow up and a detailed hormonal analysis of the patient at age 234/12 years. On no treatment, serum FSH and LH were drawn every 10 minutes for 8 hours, and estradiol and estrone levels were measured every hour during the study. Various compounds that are potential for treatment were used in transient transfection assays to determine if estrogen signaling could be induced. A personalized medicine approach was tailored to our patient, in which she received increasing doses of diethylstilbestrol (DES) with the primary endpoints being increased vaginal discharge and breast development. Follow up exams, labs, pelvic ultrasounds, DXA, and bone age X-rays were completed at various intervals up to age 234/12 years. The Bioethics Board approved this treatment. During the frequent sampling study, E2 was 604 pg/mL, E1 was 596 pg/mL, FSH was 10.0+/-0.1 IU/L (mean+/-SE), and LH was 6.7+/-0.2 IU/L. There were 3 pulses in 8 hr with an LH pulse amplitude of 2.3+/-0.5 IU/L. Although DES was shown to successfully transactivate the mutant ESR1in vitro, both in HEK293 cells and in her lymphoblastoid cells, the patient had no clinical response. After 2.5 years of treatment with increasing doses of DES, there was no vaginal discharge and breasts remained at Tanner 1. At 234/12 years, LH, FSH and E2 were unchanged. A vaginal maturation index showed a predominance of parabasal cells consistent with a lack of estrogen effect. Ultrasound showed bilateral ovarian cysts. At chronologic age 234/12 years, her bone age was 17 years and the epiphysis remained open in the ulnar bone. DXA revealed a Z-score of -2.9 at the femoral neck and -4.5 at the lumbar spine. Our findings in this severely estrogen insensitive female indicate elevated gonadotropins with normal amplitude and low frequency LH pulse dynamics in the presence of markedly increased estrogens. Treatment with DES, which stimulated estrogen signaling in vitro, did not induce secondary sexual characteristics in our patient. She remains hypoestrogenic despite the presence of ovarian cysts with a hypoestrogenic vaginal smear, absent breast development, and low bone mineral mass. Future studies will be directed towards further identification of other potential signaling mechanisms and activators of this mutant receptor.

SAT-208 Effects of Metabolic and Psychological Stressors on Serum 24-Hour Cortisol and Luteinizing Hormone

Exercising women with functional hypothalamic amenorrhea (FHA) experience disrupted luteinizing hormone pulsatility which has been linked to low energy availability. While the susceptibility to life stressors in also linked to reproductive axis suppression, the contribution of psychosocial stress to FHA in exercising women is unclear. Our aim was to prospectively determine the relations between indicators of psychosocial and metabolic stressors on the change in LH pulse dynamics during a three-month diet and exercise intervention causing moderate weight loss in previously untrained, ovulatory, collage age women studied across an academic year. We also explored the potential role of cortisol as an indicator of both metabolic and psychosocial stress in the change in LH. This is a secondary analysis from a previously published randomized, controlled trial demonstrating the causal role of low energy availability in the disruption of the menstrual cycle. Here, we report on 21 women aged (18 to 24 yrs), BMI (21.7± 1.9 kg/m2), aerobic capacity (37.5 ± 5.3 ml/kg/min) who completed a baseline menstrual cycle and three intervention menstrual cycles of a controlled diet (55% carbohydrates, 30% protein, 15% fat) and supervised aerobic exercise (5 days/wk, 30-90 min/day, 60-80% maximum heart rate). We assessed anthropometrics, aerobic capacity, psychosocial stress (Perceived Stress Scale), and metabolic hormones throughout the intervention. 24 hour LH pulse dynamics (q10 min) and diurnal patterns of cortisol (q60 min) were determined in the early follicular phase prior to the intervention and in the follicular phase of the 3rd intervention cycle or in the post intervention cycle. Pre to post comparisons were determined with paired t-tests, and Pearson bivariate correlations assessed associations. Subjects lost weight pre=57.8±4.9 kg to post=55.0±4.6 kg (p<0.001) and gained aerobic capacity pre=37.5 ± 5.3 ml/kg/min to post= 42.3 ± 5.9 ml/kg/min (p=.003). LH pulse frequency declined pre=0.79±0.23 pulses/hr to post=0.60±.29 pulses/hr (p=0.014), but mean LH and pulse amplitude were unchanged. 24 hour cortisol area under the curve increased significantly from pre=6716 ±3839 µg*day/dL to post=8515 ±2259 µg*day/dL (p=0.003). Increases in cortisol AUC were associated with a decline in LH pulse frequency R=-0.472; (p=0.048). The change in PSS was not associated with the change in LH or the change in cortisol. Body weight declines were associated with increases in cortisol AUC R= -0.473, (p=0.03) and the decline in LH pulse frequency R= 0.523; (p=0.026). These results suggest that the initial perturbation of LH pulsatility with moderate diet and exercise is largely metabolically driven and not influenced by individual responses to life stressors experienced across the academic year.

Resistin regulates reproductive hormone secretion from the ovine adenohypophysis depending on season

Work in cattle and rodents has shown that resistin, in addition to its roles in insulin resistance and inflammation, is involved in the regulation of gonadal steroidogenesis. However, the role of resistin in the regulation of reproductive processes in other species, such as seasonally breeding sheep, is completely unknown. Herein, we tested the hypothesis that resistin can influence the secretion of anterior pituitary hormones and that its effect in ewes is dependent on the day length. Thirty Polish Longwool ewes, a breed that exhibits a strong seasonal reproductive pattern, were ovariectomized with estrogen replacement using subcutaneously inserted estradiol implants. Ewes were fed ad libitum and housed under a natural photoperiod (longitude: 19°57′ E, latitude: 50° 04′ N). Intravenous treatments consisted of control or recombinant bovine resistin (rbresistin) in saline: (1) control (saline; n = 10), (2) low resistin dose (1.0 μg/kg BW; n = 10), and (3) high resistin dose (10.0 μg/kg BW; n = 10). Experiments were conducted during both short-day (SD) and long-day (LD) seasons using 5 sheep per group within each season. Blood samples were collected every 10 min over 4 h. Blood plasma concentrations of FSH, LH, and prolactin (PRL) were assayed using RIA. A season × dose interaction was observed for all hormonal variables measured. Greater concentrations (P < 0.001) of LH and FSH were observed during SDs than during LDs in all groups. During SDs, the high dose (10 μg/kg BW) decreased (P < 0.001) basal LH levels and amplitude (P < 0.05) of LH pulses and increased (P < 0.001) circulating concentrations of FSH. However, the low dose of resistin decreased (P < 0.001) FSH concentrations compared to those of controls. During LDs, both the low and high resistin doses increased mean concentrations of LH (P < 0.001 and P < 0.05, respectively) and FSH (P < 0.001). A high dose of rbresistin increased (P < 0.001) the mean circulating concentrations of PRL during both seasons. However, in all groups, concentrations of PRL were greater during LDs than SDs. These results demonstrate for the first time that resistin is involved in the regulation of pituitary hormone secretion and that this effect is differentially mediated during LDs and SDs.

Pulse and Surge Profiles of Luteinizing Hormone Secretion in the Mouse.

Using a new tail-tip bleeding procedure and a sensitive ELISA, we describe here the patterns of LH secretion throughout the mouse estrous cycle; in ovariectomized mice; in ovariectomized, estradiol-treated mice that model estrogen-negative and -positive feedback; and in transgenic GNR23 mice that exhibit allele-dependent reductions in GnRH neuron number. Pulsatile LH secretion was evident at all stages of the estrous cycle, with LH pulse frequency being approximately one pulse per hour in metestrous, diestrous, and proestrous mice but much less frequent at estrus (less than one pulse per 4 h). Ovariectomy resulted in substantial increases in basal and pulsatile LH secretion with pulses occurring approximately every 21 minutes. Chronic treatment with negative-feedback, estradiol-filled capsules returned LH pulse frequency to intact follicular phase levels, although pulse amplitude remained elevated. On the afternoon of proestrus, the LH surge was found to begin in a highly variable manner over a 4-hour range, lasting for more than 3 hours. In contrast, ovariectomized, estradiol-treated, positive-feedback mice exhibited a relatively uniform surge onset at approximately 0.5 hour prior to lights out. Gonadectomized wild-type and heterozygous GNR23 (∼200 GnRH neurons) male mice exhibited an LH pulse every 60 minutes. Homozygous GNR23 mice (∼80 GnRH neurons) had very low basal LH concentrations but continued to exhibit small amplitude LH pulses every 90 minutes. These studies provide the first characterization in mice of pulse and surge modes of LH secretion across the estrous cycle and demonstrate that very few GnRH neurons are required for pulsatile LH secretion.

Effects of long-acting GnRH antagonist, degarelix acetate, on plasma insulin-like peptide 3, testosterone and luteinizing hormone concentrations, and scrotal circumference in male goats

We recently reported that plasma insulin-like peptide 3 (INSL3) concentrations increased soon after endogenous and exogenous stimulations of LH in male goats and bulls. However, the effects of LH suppression on INSL3 secretion are unknown in domestic animals. Here, we examined the effects of a long-acting GnRH antagonist (degarelix acetate; 4 mg/kg) on the secretions of plasma INSL3 and testosterone in two phases, an immediate and a long-term phase in male goats (n = 6; aged, 13–16 months). During the immediate phase, blood was taken at 15-minute intervals for 8 hours on Days −5, 0, and 3. The GnRH antagonist was administered after 2-hour sampling of Day 0. Moreover, a daily blood sample was taken from Day 0 to Day 7, followed by twice a week until 9 weeks and finally at week 10. The scrotal circumference was recorded before treatment and continued biweekly until week 10. Concentrations of LH, INSL3, and testosterone in plasma were determined by EIA and the pulsatile nature of secretion analyzed using pulse XP software. The mean concentrations, pulse frequency (per hour), and pulse amplitude (peak-nadir) of plasma LH and testosterone reduced from pretreatment to posttreatment Day 0 and Day 3 (P < 0.05). A decline in mean concentrations, pulse frequency, and pulse amplitude of INSL3 was exhibited on posttreatment Day 3 compared with pretreatment (P < 0.01). During long-term sampling, a decline (P < 0.01) in plasma testosterone and INSL3 concentrations was observed 1 day after treatment and remained lower until 8.5 weeks after treatment, and thereafter returned to pretreatment levels. A reduction in scrotal circumference was recorded 4 weeks after treatment and remained lower until 10 weeks after treatment (P < 0.05). In conclusion, the acute regulation of INSL3 by LH was confirmed by reduction of plasma INSL3 levels within 3 days after GnRH antagonist treatment in male goats. Although the onset of suppression of testosterone was more rapid than that of INSL3, the low levels persisted for 8.5 weeks for both hormones, and subsequently the concentrations returned to pretreatment levels. A significant reduction in testicular size was also observed. The quick, long-lasting, and transient suppression of testosterone and INSL3 after a single injection implies a potential application of this antagonist in reversible long-term chemical castration in male goats.

The effect of short fasting on the hypothalamic neuronal system of kisspeptin in peripubertal female lambs

Changes in the metabolic state induced by feed restrictions have a negative effect on the reproduction in mammals and result in the delayed puberty onset. Kisspeptin (kp) has been demonstrated as a pivotal regulator of GnRH/LH secretion during puberty. To elucidate the involvement of kp in the hypothalamic secretory function in altered metabolic state, the expression of kp protein was investigated in peripubertal female lambs after short fasting. The experiment was conducted on immature 32-weeks old Merino lambs fed standard diet (n=5) or fasted for 72h (n=5). The localization and expression of kp was evaluated using immunohistochemistry. Serum LH concentration was determined using radioimmunology. In the hypothalami of fasted sheep, the number of kp perikarya and the percent of density of neuronal kp network in the caudal part of the nucleus arcuatus were significantly less (P<0.001) than in standard fed lambs. The decrease of kp axons throughout areas extending from area preoptica to medial basal hypothalamus and in the median eminence in fasted lambs compared to standard fed ones was observed. Plasma LH concentrations and amplitude of pulses decreased (P<0.05) after 3 days of fasting compared to standard fed group. The decrease of the kp expression is likely due to diminished kp protein synthesis, and its storage in the neurons. In summary, the data are the first to demonstrate interactions between metabolic status and kp neuronal system in lambs before puberty, and suggest that kp neurons may represent a link between metabolic signals and central control of reproduction.

Follicle size and reproductive hormone profiles during a post-weaning altrenogest treatment in primiparous sows

This study investigated the endocrine background of follicle size changes during post-weaning altrenogest treatment. altrenogest-treated sows received a 20-mg dosage daily at 8.00 a.m. from Day -1 to Day 14 after weaning. On Day -1, only 3/13 altrenogest-treated sows showed LH pulses compared with 8/8 control sows (P=0.001). On Day 0, control sows showed a typical high frequency-low amplitude LH pattern, indicative for recruitment of oestrogenic follicles. In altrenogest-treated animals on Day 0, half of the sows showed high frequency-high amplitude pulses from 4-5h after weaning. In altrenogest-treated sows, average follicle size increased from 3.1±0.5 mm on Day 0 to 4.4±0.6mm on Day 5, then decreased to 3.7±0.5 mm on Day 7 and stabilised thereafter. FSH and oestradiol (E2) concentrations showed a distinct diurnal pattern; high at 7.00 a.m. and low at 3.00 p.m. E2 concentrations (7.00 a.m.) showed a 2.5-fold increase from Day -1 to Day 2, and subsequently a 2-fold decline to reach a plateau at Day 8. FSH concentrations reached maximum levels by Day 5 and slowly declined afterwards. In conclusion, once-daily administration of altrenogest starting one day before weaning delays the weaning-induced increase in LH pulses. Although FSH and follicle size increase until Day 5 after weaning, follicle E2 production already decreased from Day 2 after weaning. Post-weaning altrenogest treatment thus results in a follicular wave of follicles that lose oestrogenic competence at Day 2 after weaning, presumably related to the changed LH dynamics during altrenogest treatment.

Variation in LH pulsatility during 24 h after a postweaning altrenogest treatment in relation to follicle development in primiparous sows

This study assessed pulsatile release of LH during altrenogest treatment after weaning in primiparous sows and related this to follicle development, estrus and ovulation rate. Weaned sows ( n = 10) received altrenogest 20 mg/day from D-1 to D13 (weaning = D0) at 0800 h. On D13, blood samples were collected every 12 min from 1000 until 1900 h (1st sampling period) and from 2300 h until 0800 h (2nd sampling period). During the 1st sampling period, LH concentrations remained low and no LH pulses were detected in 8/10 sows. During the 2nd sampling period, average and basal LH concentrations ( P < 0.04) and frequency of pulses ( P < 0.0001) were higher than during the 1st sampling period. Sows with short vs. long intervals to estrus (<5 days vs. ≥5 days) had higher basal and average LH concentrations during the 2nd sampling period ( P ≤ 0.004) and showed more follicular growth during treatment ( P = 0.007), generating larger follicles at D14 ( P = 0.005). Sows with high ovulation rate (≥25) displayed more LH pulses in total than sows with low (<25) ovulation rates ( P = 0.03). In conclusion, this study showed that altrenogest efficiently prevented LH pulsatility during the first bleeding period and that low frequency/high amplitude LH pulses were generally present during the second bleeding period. This variability in LH release in between two altrenogest administrations (24 h) may explain why follicular growth progresses to 5 mm during altrenogest treatments. LH pulsatility was related to length of the follicular phase and ovulation rate, which signifies its relevance.

Developmental reprogramming of reproductive and metabolic dysfunction in sheep: native steroids vs. environmental steroid receptor modulators.

The inappropriate programming of developing organ systems by exposure to excess native or environmental steroids, particularly the contamination of our environment and our food sources with synthetic endocrine disrupting chemicals that can interact with steroid receptors, is a major concern. Studies with native steroids have found that in utero exposure of sheep to excess testosterone, an oestrogen precursor, results in low birth weight offspring and leads to an array of adult reproductive/metabolic deficits manifested as cycle defects, functional hyperandrogenism, neuroendocrine/ovarian defects, insulin resistance and hypertension. Furthermore, the severity of reproductive dysfunction is amplified by excess postnatal weight gain. The constellation of adult reproductive and metabolic dysfunction in prenatal testosterone-treated sheep is similar to features seen in women with polycystic ovary syndrome. Prenatal dihydrotestosterone treatment failed to result in similar phenotype suggesting that many effects of prenatal testosterone excess are likely facilitated via aromatization to oestradiol. Similarly, exposure to environmental steroid imposters such as bisphenol A (BPA) and methoxychlor (MXC) from days 30 to 90 of gestation had long-term but differential effects. Exposure of sheep to BPA, which resulted in maternal levels of 30-50 ng/mL BPA, culminated in low birth weight offspring. These female offspring were hypergonadotropic during early postnatal life and characterized by severely dampened preovulatory LH surges. Prenatal MXC-treated females had normal birth weight and manifested delayed but normal amplitude LH surges. Importantly, the effects of BPA were evident at levels, which approximated twice the highest levels found in human maternal circulation of industrialized nations. These findings provide evidence in support of developmental origin of adult reproductive and metabolic diseases and highlight the risk posed by exposure to environmental endocrine disrupting chemicals.

Estrogen Negative Feedback on Gonadotropin Secretion: Evidence for a Direct Pituitary Effect in Women

Studies in humans and animals indicate that estrogen negative feedback occurs at the level of the hypothalamus, but it is unclear whether estrogen also exerts an inhibitory effect directly at the pituitary. The aim of the study was to determine whether estrogen has a direct negative feedback effect at the pituitary and whether this varies with aging. A GnRH antagonist and graded doses of GnRH were used to isolate pituitary responsiveness before and after estrogen administration in Clinical Research Center studies at an academic medical center. Subjects were healthy postmenopausal women aged 48-56 yr (n = 8) or 70-75 yr (n= 8). A suppressive dose of the NAL-GLU GnRH antagonist was administered, followed by graded doses of GnRH before and after 1 month of estrogen administration. LH and FSH responses to GnRH decreased after estrogen administration (P = 0.01 and P = 0.0001, respectively). The ratio of FSH to LH amplitudes decreased in response to estrogen (P = 0.04) indicating a greater sensitivity of FSH than LH to inhibition by estrogen. The inhibitory effect of estrogen on FSH was attenuated with aging (P = 0.02), but was maintained for LH (P = 0.4). Studies that control for endogenous GnRH and estradiol demonstrate a direct pituitary site of estrogen negative feedback on LH and FSH responsiveness to GnRH in women. The effect of estrogen on FSH responsiveness is greater than on LH and is attenuated with aging. These studies indicate that estrogen negative feedback occurs directly at the pituitary and contributes to the differential regulation of FSH and LH secretion.

Pulsatile Luteinizing Hormone Secretion in Women with Polycystic Ovary Syndrome under Clomiphene Citrate. Differences between Responders and Nonrespondersa , b)

Although administration of Clomiphene Citrate (CC) is an effective therapy for ovulation induction in PCO patients, 15 to 20% of PCO patients do not ovulate following CC treatment. The aim of this study was to compare the endocrine dynamics (LH pulsatile pattern, FSH and steroid hormone changes) in 6 patients who ovulated (PCOS) and 6 PCO patients who did not ovulate in response to CC (PCOR). Blood was collected at 15 min intervals for 4 hr on day 9 of the first menstrual cycle (control cycle) and on day 9 of the following (treatment) cycle. In this cycle all women received 100 mg CC/day from day 5 to day 9. LH was determined in all samples whereas FSH and estradiol were measured every 60 min. No significant differences were observed regarding the age, body mass index, degree of hirsutism, ovarian volumes and basal levels of reproductive hormones between both groups of PCO women. During the control cycle, the LH pulse amplitude and transverse LH mean concentrations in PCOR patients were higher than in PCOR patients whereas the LH pulse frequency was similar in both groups. No difference was found in FSH and estradiol values between both groups. Compared to the control cycle, PCOR patients showed no change in the pulse amplitudes and no difference in LH, FSH and estradiol values following CC treatment. In contrast, during the CC therapy in PCOS patients an increase in the LH amplitude (p less than 0.05), the transverse mean LH concentration (p less than 0.05), FSH and estradiol was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Estradiol and progesterone-induced slowing of gonadotropin-releasing hormone pulse frequency is not reversed by subsequent administration of mifepristone

Subsequent to suppression of LH (GnRH) pulse frequency by progesterone (P) and estradiol (E(2)), LH pulse frequency remains slow for 7 days after P withdrawal if mid-luteal E(2) concentrations are maintained. This may reflect an ability of E(2) to potentiate the suppressive effects of low P levels. We explored this notion in a similar experimental paradigm by administering a P-receptor antagonist (mifepristone) after P withdrawal while continuing E(2). Studies were performed in seven ovulatory, non-obese women. Transdermal E(2) (0.2 mg/day) and oral micronized P (100 mg every 8 h) were started within 24 h of the LH surge and continued for 10 days. Subjects then underwent a 13-h blood sampling protocol for determination of LH pulse characteristics and various hormone concentrations. Oral P was then discontinued, and oral mifepristone (50, 100, or 200 mg daily) and transdermal E(2) (0.2 mg/day) were administered for 7 days, after which the above sampling protocol was repeated. Results with all mifepristone doses were similar and therefore pooled. Mean LH, LH amplitude, and mean FSH markedly decreased after 7 days of mifepristone, but LH pulse frequency did not change (3.3 +/- 1.5 vs. 2.4 +/- 1.5 pulses/13 h). Prolactin and androstenedione increased between the first and second admissions, with no changes in E(2), cortisol, testosterone, or DHEAS. In conclusion, blockade of P action by mifepristone does not reverse a suppressed LH pulse frequency within 7 days when E(2) concentrations are maintained, suggesting that P withdrawal alone may not explain the luteal-follicular increase of GnRH pulse frequency.

Aging Attenuates the Pituitary Response to Gonadotropin-Releasing Hormone

Complex changes in GnRH secretion occur with aging in women, but little is known about the effect of aging on the pituitary per se. The aim of the study was to determine whether pituitary responsiveness to GnRH is attenuated with aging. A GnRH antagonist and graded doses of GnRH were used to isolate pituitary responsiveness in Clinical Research Center studies at an academic medical center. Subjects were healthy postmenopausal women (PMW) aged 48-57 yr (n = 10) or 70-77 yr (n= 9). A suppressive dose of the NAL-GLU GnRH antagonist (150 microg/kg sc) was administered and was followed by GnRH doses of 25, 75, 250, or 750 ng/kg iv every 4 h. The LH response to GnRH was attenuated with aging (P = 0.05) with an interaction between age and dose (P = 0.01) such that the LH amplitude was less in older PMW at the higher doses (250 ng/kg, 50 +/- 9 vs. 29 +/- 4.9 IU/liter, for young and old PMW, respectively, P = 0.02; and 750 ng/kg, 97.7 +/- 11 vs. 70.2 +/- 9.3 IU/liter, P = 0.002), but not the lower doses of GnRH. The FSH response to GnRH was also attenuated with aging in PMW (P = 0.005). In studies that isolated the pituitary from endogenous GnRH stimulation, aging attenuated the LH and FSH responses to exogenous GnRH in PMW. These studies indicate that the pituitary plays a role in the decline in gonadotropin levels with aging, further supporting the potential contribution of age-associated changes in both hypothalamic and pituitary function to reproductive senescence.

Overnight Luteinizing and Follicle Stimulating Hormone Profiles During GnRHa Treatment in Short Girls Born Small for Gestational Age

Since puberty starting at a height less than 140 cm might reduce adult height, postponement of puberty was studied in short pubertal girls born SGA. Data on overnight LH and FSH profiles during GnRHa treatment are very limited. To evaluate whether 3 months of GnRHa treatment results in sufficient suppression of pubertal LH and FSH profile patterns. To evaluate whether girls show sufficient pubertal suppression according to a consensus-based peak LH cut-off level of 3 IU/l during a GnRH agonist test. Twenty-one short pubertal girls born SGA. After baseline LH and FSH profiles, children received leuprorelide acetate depots of 3.75 mg subcutaneously, every 4 weeks. At baseline, amplitude and frequency of LH and FSH pulsatility were higher in girls with breast stage 3, compared to girls with breast stage 2. After 3 months of GnRHa treatment, all girls showed clinical arrest of puberty and their LH and FSH levels during overnight profiles had significantly decreased to prepubertal levels. In contrast, peak LH during the GnRH agonist test indicated insufficient pubertal suppression in 33% of girls. No differences in LH and FSH profiles were found between girls with a peak LH above or below 3 IU/l. After 3 months of GnRHa treatment, central puberty was adequately suppressed in all girls, as shown by the prepubertal LH and FSH profiles. The GnRH agonist falsely indicated insufficient pubertal suppression in 33% of these girls.

Maturation of Luteinizing Hormone (Gonadotropin-Releasing Hormone) Secretion across Puberty: Evidence for Altered Regulation in Obese Peripubertal Girls

Peripubertal obesity (body mass index-for-age >or= 95%) in girls is associated with hyperandrogenemia. LH likely contributes to this relationship, but overnight LH secretion in obese girls is poorly characterized. The aim of the study was to evaluate LH pulse characteristics in obese girls throughout pubertal maturation. We conducted a cross-sectional analysis. The study was performed in a general clinical research center. Eight nonobese and five obese Tanner 1-2 girls participated, as well as 32 nonobese and 12 obese Tanner 3-5 girls. Blood samples were collected every 10 min overnight (from 1900 to 0700 h). LH pulse frequency, amplitude, and mean LH were measured in three 4-h time blocks (block 1, 1900-2300 h; block 2, 2300-0300 h; and block 3, 0300-0700 h). Tanner stage 1-2 nonobese girls demonstrated nocturnal increases of LH frequency (P < 0.01, block 1 vs. 2) and mean LH (P < 0.05, block 1 vs. 2 and 3). Obese Tanner 1-2 girls had lower 12-h LH frequency and LH amplitude (P < 0.05 for both), with no overnight changes of LH pulse parameters. Compared to normal, LH frequency was elevated in Tanner 3-5 obese girls (P < 0.01 in all blocks), whereas LH amplitude was low (P < 0.05 in all blocks). Overnight increases of LH amplitude were observed in nonobese Tanner 3-5 girls (P < 0.0001), but not in obese Tanner 3-5 girls. Obesity in prepubertal and early pubertal girls is associated with reduced LH secretion and reduced nocturnal changes of LH. In later pubertal girls, obesity is linked with reduced LH amplitude, but elevated LH frequency; the latter may reflect effects of hyperandrogenemia.

The absence of corpus luteum formation alters the endocrine profile and affects follicular development during the first follicular wave in cattle

We previously established a bovine experimental model showing that the corpus luteum (CL) does not appear following aspiration of the preovulatory follicle before the onset of LH surge. Using this model, the present study aimed to determine the profile of follicular development and the endocrinological environment in the absence of CL with variable nadir circulating progesterone (P(4)) concentrations during the oestrous cycle in cattle. Luteolysis was induced in heifers and cows and they were assigned either to have the dominant follicle aspirated (CL-absent) or ovulation induced (CL-present). Ultrasound scanning to observe the diameter of each follicle and blood collection was performed from the day of follicular aspiration or ovulation and continued for 6 days. The CL-absent cattle maintained nadir circulating P(4) throughout the experimental period and showed a similar diameter between the largest and second largest follicle, resulting in co-dominant follicles. Oestradiol (E(2)) concentrations were greater in the CL-absent cows than in the CL-present cows at day -1, day 1 and day 2 from follicular deviation. The CL-absent cows had a higher basal concentration, area under the curve (AUC), pulse amplitude and pulse frequency of LH than the CL-present cows. After follicular deviation, the CL-absent cows showed a greater basal concentration, AUC and pulse amplitude of growth hormone (GH) than the CL-present cows. These results suggest that the absence of CL accompanying nadir circulating P(4) induces an enhancement of LH pulses, which involves the growth of the co-dominant follicles. Our results also suggest that circulating levels of P(4) and E(2) affect pulsatile GH secretion in cattle.

Inhibition of Luteinizing Hormone Secretion by Testosterone in Men Requires Aromatization for Its Pituitary But Not Its Hypothalamic Effects: Evidence from the Tandem Study of Normal and Gonadotropin-Releasing Hormone-Deficient Men

Studies on the regulation of LH secretion by sex steroids in men are conflicting. Our aims were to determine the relative contributions of testosterone (T) and estradiol (E2) to LH regulation and localize their sites of negative feedback. This was a prospective study with three arms. The study was conducted at a General Clinical Research Center. Twenty-two normal (NL) men and 11 men with GnRH deficiency due to idiopathic hypogonadotropic hypogonadism (IHH) participated. Medical castration and inhibition of aromatase were achieved using high-dose ketoconazole (KC) for 7 d with 1) no sex steroid add-back; 2) T enanthate 125 mg im starting on d 4; or 3) E2 patch 37.5 microg/d starting on d 4. Blood sampling was performed every 10 min for 12 h at baseline, overnight on d 3-4 and d 6-7. Mean LH levels, LH pulse amplitude, and GnRH pulse frequency were assessed at baseline, d 3-4, and d 6-7. In NL men, KC caused a 3-fold increase in mean LH on d 3-4, which was stable on d 6-7 with no add-back. Addition of T reduced LH levels (34.6+/-3.9 to 17.4+/-3.6 IU/liter, P<0.05) by slowing GnRH pulse frequency (13.3+/-0.4 to 6.7+/-1.0 pulses/12 h, P<0.005). LH amplitude increased (6.9+/-1.0 to 12.1+/-1.4 IU/liter, P<0.005). E2 add-back suppressed LH levels (36.4+/-5.6 to 19.0+/-2.4 IU/liter, P<0.005), by slowing GnRH pulse frequency (11.4+/-0.2 to 8.6+/-0.4 pulses/12 h, P<0.05) and had no impact on LH pulse amplitude. In IHH men, restoring normal T levels caused no suppression of mean LH levels or LH amplitude. E2 add-back normalized mean LH levels and decreased LH amplitude from 14.7+/-1.7 to 12+/-1.5 IU/liter (P<0.05). 1) T and E2 have independent effects on LH. 2) Inhibition of LH by T requires aromatization for its pituitary, but not hypothalamic effects. 3) E2 negative feedback on LH occurs at the hypothalamus.