Pattern Of LH Secretion Research Articles

Goats as Valuable Animal Model to Test the Targeted Glutamate Supplementation upon Antral Follicle Number, Ovulation Rate, and LH-Pulsatility.

Simple SummaryExogenous glutamate administration to yearling-anestrous goats enhanced not only ovarian function (i.e., ovulation rate and antral follicle number) but also denoted undoubted effects at the hypothalamic-pituitary level, augmenting LH pulsatility. Our results show not only the use of glutamate as a clean alternative but also as an interesting reproductive strategy to amplify ovarian function, considering goats as an animal model. While this should enlarge the possibility of escalating our knowledge regarding the hypothalamic-pituitary-gonadal modulation by glutamate, such research outcomes may also embrace potential translational implications.The potential effect of intravenous administration of glutamate on the ovarian activity and the LH secretion pattern, considering the anestrous yearling goat as an animal model, were assessed. In late April, yearling goats (n = 20) were randomly assigned to either (1) Glutamate supplemented (GLUT; n = 10, Live Weight (LW) = 29.6 ± 1.02 kg, Body Condition (BCS) = 3.4 ± 0.2 units; i.v. supplemented with 7 mg GLUT kg−1 LW) or (2) Non-supplemented (CONT; n = 10; LW = 29.2 ± 1.07 kg, BCS = 3.5 ± 0.2 units; i.v. saline). The oats were estrus-synchronized; blood sampling (6 h × 15 min) was carried out for LH quantification. Response variables included pulsatility (PULSE), time to first pulse (TTFP), amplitude (AMPL), nadir (NAD), and area under the curve (AUC) of LH. Ovaries were ultra-sonographically scanned to assess ovulation rate (OR), number of antral follicles (AF), and total ovarian activity (TOA = OR + AF). LH-PULSE was quantified with the Munro algorithm; significant treatment x time interactions were evaluated across time. The variables LW and BCS did not differ (p > 0.05) between the experimental groups. Nevertheless, OR (1.77 vs. 0.87 ± 0.20 units), TOA (4.11 vs. 1.87 ± 0.47 units) and LH-PULSE (5.0 vs. 2.2 pulses 6 h-1) favored (p < 0.05) to the GLUT group. Our results reveal that targeted glutamate supplementation, the main central nervous system neurotransmitter, arose as an interesting strategy to enhance the hypothalamic–hypophyseal–ovarian response considering the anestrous-yearling goat as an animal model, with thought-provoking while promising translational applications.

Endocrineand follicular studies in Meishan pig

The enhanced early embryonic survival in Chinese Meishan compared with Large- White gilts may be due, in part, to differences in ovarian and endocrine function, particularly during the periovulatory period. The overall patterns of oestradiol, LH and FSH secretion were not different between Meishan and Large-White hybrid controls during this period, although circulating inhibin concentrations were higher in Meishan gilts. Thus, there appeared to be a decreased sensitivity to inhibin feedback on FSH secretion in Meishan gilts. Behavioural oestrus was exhibited earlier relative to the LH surge in Meishan gilts than in Large-White hybrid gilts, but the time interval from the oestradiol peak until the LH surge was similar in both breeds. This finding suggests that Meishan gilts are more sensitive in terms of initiating a behavioural response, but not in terms of positive feedback. Although preovulatory follicular characteristics were as variable in Meishan as in Large-White hybrid gilts, follicles from Meishan gilts were smaller, but contained a higher concentration of oestradiol in the follicular fluid. This was probably due to increased aromatase activity in both granulosa and theca cells of Meishan follicles. The enhanced maturation of the intrafollicular environment in Meishan gilts was reflected in the oocyte population which was at a more advanced stage of development in the period preceding ovulation. In addition to decreasing the time between onset of oestrus and ovulation, advancing the LH surge to coincide with onset of oestrus (via hCG administration) decreased embryo survival at day 30 of gestation. It is concluded that both endocrine and follicular mechanisms have a role in ensuring the prolificacy in the Meishan breed.

Endocrine patterns associated with puberty in male and female cattle

In four studies secretion patterns of LH, FSH, prolactin, testosterone and progesterone were measured in male and female cattle to determine endocrine changes associated with sexual maturation. Two periods of increasing gonadotrophin secretion were observed, the second one coinciding with puberty. A short luteal phase of 8-12 days precedes the first oestrus at 10-11 or 14 months of age. The testosterone values of the bulls increased with age from 5-6 months. Prolactin levels in the bulls increased at the time of the first testosterone rise. A frequency of about 1-2 LH and FSH pulses/8 h occurred at 1, 2, 5 and 10 months of age. The pituitary response to GnRH (1 microgram/kg i.v.) was tested in 2 male and 2 female calves at monthly intervals. LH and FSH were released at all ages but a reduced FSH response occurred in both sexes after the 5th month. A small testosterone release was observed as early as 1 month after birth in males similar to those observed after endogenous LH pulses. We conclude that the initiation of puberty in both sexes is controlled by the same neuroendocrine mechanisms. The pituitary gland, ovaries and testes are already able to respond to specific stimuli long before puberty, and they may also be involved indirectly due to changes in the feedback system modulating gonadotrophin secretion.

The Relationship Between Progesterone, Sleep, and LH and FSH Secretory Dynamics in Early Postmenarchal Girls.

During puberty, LH pulse frequency increases during sleep; in women, LH pulse frequency slows during sleep in the early/middle follicular phase (FP) of the menstrual cycle. The origin and significance of this developmental transition are unknown. To determine the relationship between progesterone (P4) exposure, sleep-related slowing of LH pulses in the FP, and the intercycle FSH rise, which promotes folliculogenesis, in early postmenarchal girls. 23 girls (gynecologic age 0.4 to 3.5 years) underwent hormone measurements and pelvic ultrasounds during two consecutive cycles and one frequent blood sampling study with concurrent polysomnography during the FP. Subjects demonstrated one of four patterns during cycle 1 that represent a continuum of P4 exposure: ovulatory cycles with normal or short luteal phase lengths or anovulatory cycles ± follicle luteinization. Peak serum P4 and urine pregnanediol (Pd) in cycle 1 were inversely correlated with LH pulse frequency during sleep in the FP of cycle 2 (r = -0.5; P = 0.02 for both). The intercycle FSH rise and folliculogenesis in cycle 2 were maintained after anovulatory cycles without P4 or Pd exposure or nocturnal slowing of LH pulse frequency in the FP. During late puberty, rising P4 levels from follicle luteinization and ovulation may promote a slower LH pulse frequency during sleep in the FP. However, a normal FSH rise and follicle growth can occur in the absence of P4-associated slowing. These studies therefore suggest that an immature LH secretory pattern during sleep is unlikely to contribute to menstrual irregularity in the early postmenarchal years.

Aging has the opposite effect on cAMP and cGMP circadian variations in rat Leydig cells.

The Leydig cell physiology displays a circadian rhythm driven by a complex interaction of the reproductive axis hormones and circadian system. The final output of this regulatory process is circadian pattern of steroidogenic genes expression and testosterone production. Aging gradually decreases robustness of rhythmic testosterone secretion without change in pattern of LH secretion. Here, we analyzed effect of aging on circadian variation of cAMP and cGMP signaling in Leydig cells. Results showed opposite effect of aging on cAMP and cGMP daily variation. Reduced amplitude of cAMP circadian oscillation was probably associated with changed expression of genes involved in cAMP production (increased circadian pattern of Adcy7, Adcy9, Adcy10 and decreased Adcy3); cAMP degradation (increased Pde4a, decreased Pde8b, canceled rhythm of Pde4d, completely reversed circadian pattern of Pde7b and Pde8a); and circadian expression of protein kinase A subunits (Prkac/PRKAC and Prkar2a). Aging stimulates expression of genes responsible for cGMP production (Nos2, Gucy1a3 and Gucy1b3/GUCYB3) and degradation (Pde5a, Pde6a and Pde6h) but the overall net effect is elevation of cGMP circadian oscillations in Leydig cells. In addition, the expression of cGMP-dependent kinase, Prkg1/PRKG1 is up-regulated. It seems that aging potentiate cGMP- and reduce cAMP-signaling in Leydig cells. Since both signaling pathways affect testosterone production and clockwork in the cells, further insights into these signaling pathways will help to unravel disorders linked to the circadian timing system, aging and reproduction.

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.

Temporary undernutrition during early gestation, corpora lutea morphometrics, ovarian progesterone secretion and embryo survival in gilts.

The present study reports effects of severe undernutrition on luteal function and pregnancy in pigs. Gilts were inseminated and either fasted on Day 10 and 11 after conception (n=11) or fully fed throughout (n=10). Fasting did not affect LH or progesterone pulsatile secretion pattern on Day 11 in samples taken from blood vessels draining an ovary. Ultrasonographic measurements of the size of the corpora lutea did not show any effect of fasting either. However, fasted gilts had 10 to 30% lower systemic progesterone from Day 12 through Day 15 after conception (P<0.05). All gilts farrowed, but fasted gilts had fewer born piglets than fully fed gilts (8.8±0.8 vs 10.9±0.5 respectively; P<0.05). In conclusion, fasting during embryo elongation can compromise embryonic survival by affecting ovarian function in the days after fasting, without having an immediate effect on LH secretion and progesterone output by the ovaries.

Acute regulation of plasma insulin-like peptide 3 concentrations by luteinizing hormone in male goats

Recently, it was reported that in bulls secretion of insulin-like peptide 3 (INSL3) in blood occurred in a pulsatile manner and was acutely regulated by LH. In the present study, the acute regulation of plasma INSL3 and its temporal relationships with LH and testosterone were examined in six sexually matured male goats using the following experimental design. (1) After stimulating LH release by administering a GnRH analogue, blood levels of LH, INSL3, and testosterone were monitored at 15-minute intervals for 2 hours followed by hourly intervals up to 8 hours. (2) After activation of the LH receptor by hCG blood levels of INSL3 and testosterone were determine at 15-minute intervals for 2 hours, followed by hourly intervals up to 8 hours, daily intervals up to Day 8, and finally on Day 12. (3) The release of LH, INSL3, and testosterone in normal physiology was established at 15-minute intervals for an 8-hour session. Concentrations of LH, INSL3, and testosterone in plasma were measured by enzyme-immunoassays. After GnRH treatment, mean plasma concentrations of all three hormones increased (P < 0.05) dramatically from 30 minutes and remained high until 120 minutes (LH), 75 minutes (INSL3), and 4 hours (testosterone) after treatment. After hCG treatment, mean plasma INSL3 concentrations increased (P < 0.05) from 30 minutes and remained elevated until the end of sampling on Day 12. An increase (P < 0.05) in mean plasma testosterone concentrations occurred from 15 minutes and remained high until Day 6. The mean increase (maximum per pretreatment concentration) of INSL3 concentrations after administration of GnRH and hCG was lower (P < 0.01) than that of testosterone. The secretory pattern of LH, INSL3, and testosterone in the general circulation was pulsatile with a frequency of 5.5 ± 0.6, 4.7 ± 0.5, and 2.2 ± 0.5, respectively, during the 8-hour period. Twenty out of 28 (71%) of these INSL3 pulses peaked within 1 hour after a peak of an LH pulse. The mean increase (peak per basal concentration) of INSL3 pulses (2.1 ± 0.1 fold, n = 28) was lower (P < 0.01) than that of testosterone pulses (4.3 ± 2.2 fold, n = 13). In conclusion, secretion of INSL3 in blood occurred, like in bulls, in a pulsatile manner soon after LH pulses in male goats. The absolute concentrations of INSL3 in male goats were higher than that reported in other mammals. Insulin-like peptide 3 concentrations were acutely increased by endogenous and exogenous LH in male goats, but the rise of INSL3 was lower than that of testosterone.

Luteotrophic effect of ovulation-inducing factor/nerve growth factor present in the seminal plasma of llamas

The hypothesis that ovulation-inducing factor/nerve growth factor (OIF/NGF) isolated from llama seminal plasma exerts a luteotrophic effect was tested by examining changes in circulating concentrations of LH and progesterone, and the vascular perfusion of the ovulatory follicle and developing CL. Female llamas with a growing follicle of 8 mm or greater in diameter were assigned randomly to one of three groups (n = 10 llamas per group) and given a single intramuscular dose of PBS (1 mL), GnRH (50 μg), or purified OIF/NGF (1.0 mg). Cineloops of ultrasonographic images of the ovary containing the dominant follicle were recorded in brightness and power Doppler modalities. Llamas were examined every 4 hours from the day of treatment (Day 0) until ovulation, and every other day thereafter to Day 16. Still frames were extracted from cineloops for computer-assisted analysis of the vascular area of the preovulatory follicle from treatment to ovulation and of the growing and regressing phases of subsequent CL development. Blood samples were collected for the measurement of plasma LH and progesterone concentrations. The diameter of the dominant follicle at the time of treatment did not differ among groups (P = 0.48). No ovulations were detected in the PBS group but were detected in all llamas given GnRH or OIF/NGF (0/10, 10/10, and 10/10, respectively; P < 0.0001). No difference was detected between the GnRH and OIF/NGF groups in the interval from treatment to ovulation (32.0 ± 1.9 and 30.4 ± 5.7 hours, respectively; P = 0.41) or in maximum CL diameter (13.1 ± 0.4 and 13.5 ± 0.3 mm, respectively; P = 0.44). The preovulatory follicle of llamas treated with OIF/NGF had a greater vascular area at 4 hours after treatment than that of the GnRH group (P < 0.001). Similarly, the luteal tissue of llamas treated with purified OIF/NGF had a greater vascular area than that of the GnRH group on Day 6 after treatment (P < 0.001). The preovulatory surge in plasma LH concentration began, and peaked 1 to 2 hours later in the OIF/NGF group than in the GnRH group (P < 0.05). Plasma progesterone concentration was higher on Day 6 in the OIF/NGF group than in the GnRH group (P < 0.001). Results support the hypothesis that OIF/NGF exerts a luteotrophic effect by altering the secretion pattern of LH and enhancing tissue vascularization during the periovulatory period and early stages of CL development.

The pattern of LH secretion and the ovarian response to the ‘ram effect’ in the anoestrous ewe is influenced by body condition but not by short-term nutritional supplementation

In sheep, the 'ram effect' induces out-of-season fertility and good nutrition increases prolificacy. This experiment determined if fatness or short-term nutritional supplementation modified the response to the 'ram effect'. A group of 48 Île-de-France ewes were fed diets that produced groups with body-condition scores (BCS) of >3.0 and <2.0. Within each BCS group animals were supplemented daily with 500g of lupins from Day -5 to Day 0 (ram introduction) resulting in four groups: low BCS, supplemented (n=7) and non-supplemented (n=8) and high BCS, supplemented (n=12) and non-supplemented (n=11). The blood concentrations of glucose and insulin and the LH response to gonadotrophin-releasing hormone (GnRH) were determined. After the 'ram effect' the pattern of LH pulsatility, the LH surge and ovarian responses were analysed. Low BCS ewes had lower glucose and insulin (P<0.001) and supplementation increased both (P≤0.001). The increase in LH induced by GnRH was reduced in low BCS ewes (P=0.015) but it was not affected by supplementation. Similarly, LH pulsatility was reduced in low BCS ewes (P<0.05). The LH surge and ovarian cyclicity were not affected but the follow-up cycle was delayed (P=0.034) and progesterone was reduced (P=0.029) in low BCS ewes. There was an effect of BCS on ovulation rate (P<0.05). These results show that the BCS can modify the response to the 'ram effect' and that supplementation has little effect on this response.

Acupuncture for ovulation induction in polycystic ovary syndrome: a randomized controlled trial

Acupuncture has been demonstrated to improve menstrual frequency and to decrease circulating testosterone in women with polycystic ovary syndrome (PCOS). Our aim was to investigate whether acupuncture affects ovulation frequency and to understand the underlying mechanisms of any such effect by analyzing LH and sex steroid secretion in women with PCOS. This prospective, randomized, controlled clinical trial was conducted between June 2009 and September 2010. Thirty-two women with PCOS were randomized to receive either acupuncture with manual and low-frequency electrical stimulation or to meetings with a physical therapist twice a week for 10-13 wk. Main outcome measures were changes in LH secretion patterns from baseline to after 10-13 wk of treatment and ovulation frequency during the treatment period. Secondary outcomes were changes in the secretion of sex steroids, anti-Müllerian hormone, inhibin B, and serum cortisol. Ovulation frequency during treatment was higher in the acupuncture group than in the control group. After 10-13 wk of intervention, circulating levels of estrone, estrone sulfate, estradiol, dehydroepiandrosterone, dehydroepiandrosterone sulfate, androstenedione, testosterone, free testosterone, dihydrotestosterone, androsterone glucuronide, androstane-3α,17β-diol-3-glucuronide, and androstane-3α,17β-diol-17-glucuronide decreased within the acupuncture group and were significantly lower than in the control group for all of these except androstenedione. We conclude that repeated acupuncture treatments resulted in higher ovulation frequency in lean/overweight women with PCOS and were more effective than just meeting with the therapist. Ovarian and adrenal sex steroid serum levels were reduced with no effect on LH secretion.

Effects of equine chorionic gonadotropin on follicle development and pregnancy rates in suckled beef cows with or without calf removal1

Two experiments were conducted to evaluate the effects of eCG, temporary 72-h calf removal (CR), or both on dominant follicle (DF) diameter and pregnancy rates (PR) in suckled beef cows. For Exp. 1, we hypothesized that CR, eCG, or both at PGF2α administration concomitant with synchronization of ovulation protocol would increase DF diameter and alter patterns of LH, estradiol (E), and progesterone (P4) secretion. Thirty-five multiparous, suckled crossbred beef cows were assigned randomly to a 2 × 2 factorial arrangement of 4 treatments: 1) cows received 100 μg GnRH and a controlled internal drug release (CIDR) insert containing 1.38 g of P4 (d -7) followed in 7 d by 25 mg PGF(2α) and CIDR removal (d 0) followed in 72 h by GnRH and fixed-time AI (d 3; Control; n = 9); 2) similar to control, but calves were removed from their dams for 72 h between d 0 and 3 (COCR; n = 9); 3) similar to control, but cows received 400 IU eCG on d 0 (COeCG; n = 9); and 4) similar to COCR, but cows received 400 IU eCG on d 0 (eCGCR; n = 8). Blood sample collection and ovary scans were performed on d -14, -7, 0, 1, 2, 3, 4, and 10. Pregnancy rate, ovulation response by d 4, and peak concentrations of LH before 72 h after PGF(2α) were greater (P < 0.05) for cows exposed to CR (COCR and eCGCR) than for cows not exposed to CR (Control and COeCG). Follicle diameter on d 3 was greater (P = 0.02) for cows receiving eCG (COeCG and COeCG; 14.9 ± 0.5 mm) than for cows receiving no eCG (Control and COCR; 13.1 ± 0.5 mm). Concentrations of E were greater (P < 0.05) at 32 h for COCR (8.2 ± 1.0 pg/mL) and eCGCR (8.5 ± 0.9 pg/mL) than in Control (4.9 ± 1.2 pg/mL) and COeCG (4.6 ± 1.1 pg/mL) and at 44 h after PGF(2α) for eCGCR (11.7 ± 1.6 pg/mL) compared with Control (6.9 ± 1.7 pg/mL), COCR (7.1 ± 1.5 pg/mL), and COeCG (7.5 ± 1.7 pg/mL). In Exp. 2, we determined whether administration of 200 IU eCG improved PR in suckled beef cows. The Control (n = 261) and COeCG (n = 252) treatments were similar to those previously described in Exp. 1; however, the interval from PGF(2α) to fixed-time AI was 66 h and 200 IU of eCG were administered to the COeCG group. Pregnancy rates did not differ (P > 0.10) between COeCG (43%) and Control (50%). We conclude that eCG increased DF diameter and CR resulted in a greater percentage of cows experiencing LH peak before 72 h after PGF(2α) and ovulation response; however, eCG failed to improve PR to timed AI.

Elevated androgens during puberty in female rhesus monkeys lead to increased neuronal drive to the reproductive axis: a possible component of polycystic ovary syndrome

Hyperandrogenemia is associated with several clinical disorders in which both reproductive dysfunction and metabolic changes may coexist [i.e. polycystic ovary syndrome (PCOS), obesity and congenital adrenal hyperplasia]. Moreover, there is growing evidence that the elevated levels of circulating androgens in obese girls may lead to an increased neuroendocrine drive to the reproductive axis, similar to that associated with PCOS. To test whether androgen exposure in the childhood and adolescent period could lead to pubertal alterations in LH secretory patterns, female rhesus monkeys received subcutaneous testosterone implants prepubertally beginning at 1 year of age, maintaining a 3.7-fold increase (P = 0.001) in circulating testosterone levels over cholesterol-implant controls (n = 6/group) into the post-pubertal period. In early adulthood, pulsatile secretion of LH was measured over 12 h during the early follicular phase of a menstrual cycle, and responsiveness of the pituitary to gonadotrophin-releasing hormone was determined. In addition, ultrasounds were performed to assess ovarian morphology and glucose tolerance testing was performed to assess insulin sensitivity. The timing of menarche was similar between groups. Testosterone-treated animals had a significantly greater LH pulse frequency during the early follicular phase compared with controls (P = 0.039) when measured at 5 years of age. There was a larger LH response to GnRH when testosterone-treated animals were 4 years of age (P = 0.042), but not when the animals were 5 years old (P = 0.57). No differences were seen in insulin sensitivity or ovarian morphology, and the groups showed similar rates of ovulation in early adulthood. Exposure to increased levels of androgens over the course of pubertal development appears to trigger physiological changes in the neural drive to the reproductive axis that resemble those of obese hyperandrogenemic girls in early adulthood and are characteristic of PCOS.

The Long-Term Clinical Follow-Up and Natural History of Men with Adult-Onset Idiopathic Hypogonadotropic Hypogonadism

Adult-onset idiopathic hypogonadotropic hypogonadism (AHH) is a rare disorder characterized by an isolated failure of gonadotropin secretion occurring after an otherwise normal sexual maturation in men. This study aims to examine the etiology and long-term natural history of this disorder. Long-term follow up, including detailed clinical, biochemical, and genetic examinations, were performed and compared with those at diagnosis. Patients included 10 men with AHH [serum testosterone (T) <125 ng/dl]. Overnight neuroendocrine studies, semen fluid analyses, and genetic screening were performed (KAL1, FGFR1, PROK2, PROKR2, NELF, TAC3, TACR3, and GNRH1) over a decade of longitudinal follow up. Follow-up evaluations were conducted 10.6 +/- 5.9 yr after initial studies and revealed that the clinical characteristics and seminal fluid analyses of AHH men (body mass index, 28.8 +/- 4.1 vs. 27.0 +/- 4.3 kg/m(2); testicular volume, 18 +/- 6 vs. 19 +/- 6 ml) do not change over a decade with no spontaneous reversals. Several men exhibited some variability in their endogenous GnRH-induced LH secretory patterns, including emergence of endogenous pulsatility in three individuals. However, all remained hypogonadal (T < or =130 ng/dl). A single heterozygous DNA sequence change in PROKR2 (V317L) was identified, although this rare sequence variant did not prove to be functionally abnormal in vitro. Seven days of pulsatile GnRH therapy in this subject nearly normalized his serum T, supporting that the site of the defect is hypothalamic and not pituitary. 1) AHH in men appears to be a long-lasting condition. 2) Although minor changes in the abnormal pattern of endogenous GnRH-induced LH secretion occurred in some AHH patients, all remained frankly hypogonadal.

Pulsed GnRH secretion and the FSH secretory peaks that initiate ovarian antral follicular wave emergence in anestrous ewes

In ewes, immunization against GnRH blocks LH pulses but mean serum FSH concentrations are only partly reduced; the fate of the FSH peaks that precede ovarian follicular waves has not been studied. In this study, we used immunization against GnRH to examine the need for pulsed GnRH secretion in the genesis of FSH peaks in the anestrous ewe. Six anestrous ewes were given a GnRH immunogen on Day 0 and a booster injection on Day 28. Control ewes ( n = 6) received adjuvant only. Transrectal ultrasonography was performed daily for 2 days prior to and 10 days following both the primary (Days −2 to 10) and booster (Days 26–38) injections and for a 13-day period beginning 26 days after booster injection (Days 54–66). Blood samples were collected daily. Intensive bleeding (every 12 min for 7 h) was performed on Days 9, 37, and 65 of the experimental period to characterize the pulsatile pattern of LH secretion. GnRH antibody titers were increased and LH pulses were abolished immediately after booster immunization ( P < 0.05). The number of FSH peaks, FSH peak concentration and amplitude and basal FSH concentrations were only decreased in immunized ewes in the period of observations starting 26 days after booster immunization ( P < 0.05); however, some peaks were still seen. The number of follicular waves was decreased in the period around booster immunization and no follicular waves were seen during the period starting 26 days after booster immunization in immunized ewes ( P < 0.05). In summary, in anestrous ewes, when pulsed LH secretion was abolished by immunization against GnRH, the peaks in serum concentrations of FSH that trigger ovarian follicular waves continued for a period of time. We concluded that although blocking the effects of GnRH gradually causes a diminution of FSH secretion, there is no acute requirement for GnRH in the regulation of FSH peaks. The existence of FSH peaks in the absence of follicular waves, and pulsed LH secretion, suggests that some endogenous rhythm may drive the occurrence of FSH peaks, independent of both changes in negative feedback by secretory products from ovarian antral follicles and GnRH.

Role of Seminiferous Tubular Development in Determining the FSH versus LH Responsiveness to GnRH in Early Sexual Maturation

Background: The onset of sexual maturation at puberty is a unique developmental period from a neuroendocrine perspective in that it is characterized by enhanced FSH secretion and FSH responsiveness to exogenous GnRH (vs. LH) from the gonadotrope, yet the mechanism of these dynamics remains unclear. This study aimed to elucidate this phenomenon using a human disease model of GnRH deficiency (idiopathic hypogonadotropic hypogonadism, IHH) in which GnRH input can be experimentally controlled. Methods: 25 GnRH-deficient men were selected for study based upon their baseline testicular volumes (TV) and serum inhibin B (I_B) levels to represent a spectrum of pubertal/testicular development. Subjects underwent: (i) a 12-hour overnight neuroendocrine evaluation for hormonal profiling and determination of endogenous LH secretion pattern, and (ii) a 7-day exposure to a physiologic regimen of exogenous pulsatile GnRH (25 ng/kg every 2 h). Daily measurements of serum testosterone (T) and I_B levels were made and a 2-hour window of frequent blood sampling was monitored to measure LH and FSH following a single i.v. GnRH bolus (25 ng/kg). All subjects were screened for known loci underlying GnRH deficiency and the response to GnRH was tracked according to genotype. Results: Among the entire cohort, no changes were noted in serum T or I_B during the 7 days, thus keeping gonadal feedback relatively constant. However, serum LH and FSH levels increased significantly (p < 0.0001) in the entire cohort. When analyzed by degree of pubertal/testicular development, men with no evidence of prior spontaneous pubertal development (TV ≤3 ml, Group I) showed sharp increases in serum FSH compared to men with some prior evidence of partial puberty (TV >3 ml, Group II, p < 0.0001). Group I exhibited a decreased LH response to GnRH on day 2 compared to day 1 (p < 0.01), which did not recover until day 5 (1–4 vs. 5–7 days, p < 0.0001). Group II displayed robust and equivalent LH responses to GnRH throughout the 7-day study. Genetic studies identified 8 mutations in 4 different loci (DAX1, KAL1, GNRHR, and FGFR1) in this cohort. Conclusions: GnRH-deficient men undergoing GnRH-induced sexual maturation display an inverse relationship between FSH responsiveness to GnRH and baseline testicular size and I_B levels. This observation implies that increasing seminiferous tubule maturity represents the major constraint on FSH responsiveness to GnRH in early puberty. In contrast, LH responsiveness to GnRH correlates directly with duration of GnRH exposure. Attenuated pituitary gonadotropin responses were noted in subjects harboring DAX1 mutations, consistent with known pituitary defects.

Circadian Regulation of Kiss1 Neurons: Implications for Timing the Preovulatory Gonadotropin-Releasing Hormone/Luteinizing Hormone Surge

The preovulatory GnRH/LH surge depends on the presence of estradiol (E(2)) and is gated by a circadian oscillator in the suprachiasmatic nucleus (SCN) that causes the surge to occur within a specific temporal window. Although the mechanisms by which the clock times the LH surge are unclear, evidence suggests that the SCN is linked to GnRH neurons through a multisynaptic pathway that includes neurons in the anteroventral periventricular nucleus (AVPV). Recently, Kiss1 neurons in the AVPV have been implicated in the surge mechanism, suggesting that they may integrate circadian and E(2) signals to generate the LH surge. We tested whether Kiss1 neurons display circadian patterns of regulation in synchrony with the temporal pattern of LH secretion. Mice housed in 14 h light, 10 h dark were ovariectomized, given E(2) capsules (or nothing), and transferred into constant darkness. Two days later, the mice were killed at various times of day and their LH and Kiss1 levels assessed. In E(2)-treated females, LH levels were low except during late subjective day (indicative of an LH surge). Similarly, AVPV Kiss1 expression and c-fos coexpression in Kiss1 neurons showed circadian patterns that peaked coincident with LH. These temporal changes in Kiss1 neurons occurred under steady-state E(2) and constant environmental conditions, suggesting that Kiss1 neurons are regulated by circadian signals. In the absence of E(2), animals displayed no circadian pattern in LH secretion or Kiss1 expression. Collectively, these findings suggest that the LH surge is controlled by AVPV Kiss1 neurons whose activity is gated by SCN signals in an E(2)-dependent manner.

Pulse Pattern of Luteinizing Hormone (LH) in Patients with Varicocele: A Preliminary Report/Puls-Muster für LH bei Patienten mit Varikocele

Serum concentrations of LH were measured every 20 minutes for 6 hours in 4 varicocele patients and 4 control subjects. In both groups, a pulsatile pattern of LH secretion was observed. Also in the two groups, LH pulse rate (2-5/6 hour) and amplitude (23.5-61%) were identical. These findings suggest that Gonadotrophin releasing hormone (Gn RH) and LH secretions have no role in the deranged sperm parameters often found in infertile men with varicocele.

Impaired episodic LH secretion in female mice with GFP in GnRH neurons

The ability to assess the activity of gonadotropin-releasing hormone (GnRH) neurons has been greatly enhanced by transgenic animal models with targeted expression of green fluorescent protein (GFP). However, it has yet to be demonstrated that the GnRH system continues to exhibit a full range of normal physiological functions in the presence of such genetic manipulation. Accordingly, we have used repetitive blood sampling via indwelling venous catheters to define LH secretory patterns in normal and transgenic mice. Transgenic females proved to be reproductively competent as defined by fecundity, appropriate cyclic changes in vaginal cytology in intact adult females, and spontaneous LH surges as well as surges in response to steroid or mating stimuli. The expression of c-fos following such steroid treatment and mating in ovariectomized transgenics was similar to the expression previously reported in nontransgenic mice. Likewise, the percentage of retrogradely labeled GnRH neurons was similar to that reported in nontransgenic mice. However, episodic LH secretion, an index of GnRH pulse generator activity, was dramatically compromised in ovariectomized female transgenics compared with C57BL6 controls of both sexes and castrated transgenic males. Taken together, these findings suggest that the GnRH pulse generator is selectively impaired in ovariectomized females in which GnRH neurons express GFP.

Effects of Feeding Level During Lactation on FSH and LH Secretion Patterns, and Follicular Development in Primiparous Sows

In the primiparous lactating sow undernutrition affects LH, but the effect on FSH is less clear. This study was conducted to investigate the effect of ad libitum (AL; n = 5) and restricted (RE; 70% of the AL feed; n = 5) feeding on the secretion patterns of FSH and LH, and on follicular development in primiparous lactating sows. Body side fat thickness (BSFT) was measured prior to farrowing and at weaning on day 21 postpartum (pp). Sows had an intravenous catheter fitted on day 6 or 7 pp. Blood samples were taken on days 12, 15 and 18 pp, every 15 min starting at 0700 h for 11 h, and plasma analysed for FSH and LH by radioimmunoassay (RIA). Daily transcutaneous ultrasonography of the ovaries was performed between days 10 and 20 pp to monitor follicular growth. Reduction in BSFT was higher in RE than in AL sows (p < 0.05). Mean and basal LH were significantly higher in AL than in RE sows on days 12 and 15 pp. (p < 0.05), and LH pulse frequency tended to be higher (p < 0.1). Mean FSH was higher in AL than in RE sows on days 15 and 18 (p < 0.05), and had a tendency to be higher on day 12 (p = 0.1). Follicle size increased in AL sows between days 10 and 20 of lactation (p < 0.05; r = 0.71), but remained unaffected in RE sows. In conclusion, the study demonstrates that feed restriction of primiparous sows during lactation affects not only LH, but also FSH, as well as lactational follicular growth. An association between those events is suggested.