Doses Of Gonadotropin-releasing Hormone Research Articles

Effect of progesterone on magnitude of the luteinizing hormone surge induced by two different doses of gonadotropin-releasing hormone in lactating dairy cows

Ovulation to the first GnRH injection of Ovsynch-type protocols is lower in cows with high progesterone (P4) concentrations compared with cows with low P4 concentrations, suggesting that P4 may suppress the release of LH from the anterior pituitary after GnRH treatment. The objectives of this study were to determine the effect of 1) circulating P4 concentrations at the time of GnRH treatment on GnRH-induced LH secretion in lactating dairy cows and 2) increasing the dose of GnRH from 100 to 200μg on LH secretion in a high- and low-P4 environment. A Double-Ovsynch (Pre-Ovsynch: GnRH, PGF2α 7d later, GnRH 3d later, and Breeding-Ovsynch 7d later: GnRH, PGF2α 7d later, and GnRH 48h later) synchronization protocol was used to create the high- and low-P4 environments. At the first GnRH injection of Breeding-Ovsynch (high P4), all cows with a corpus luteum ≥20mm were randomly assigned to receive 100 or 200μg of GnRH. At the second GnRH injection of Breeding-Ovsynch (low P4) cows were again randomized to receive 100 or 200μg of GnRH. Blood samples were collected every 15min from −15 to 180min after GnRH treatment, and then hourly until 6h after GnRH treatment. As expected, mean P4 concentrations were greater for cows in the high- than the low-P4 environment. For cows receiving 100μg of GnRH, the LH peak and area under the curve (AUC) were greater in the low- than in the high-P4 environment. Similarly, for cows receiving 200μg of GnRH, the LH peak and AUC were greater in the low- than the high-P4 environment. Cows receiving 100 or 200μg of GnRH had greater mean LH concentration in the low- than the high-P4 environment from 1 to 6h after GnRH treatment. On the other hand, when comparing the effect of the 2 GnRH doses in the high- and low-P4 environments, cows receiving 200μg of GnRH had a greater LH peak and AUC than cows treated with 100μg of GnRH both in the high- and low-P4 environments. For the high-P4 environment, mean LH was greater from 1.5 to 5h after GnRH treatment for cows receiving 200μg of GnRH than for those receiving 100μg of GnRH. In the low-P4 environment, mean LH was greater for cows receiving 200μg of GnRH than for those receiving 100μg of GnRH from 1 to 2.5h after GnRH treatment. We conclude that the P4 environment at GnRH treatment dramatically affects GnRH-induced LH secretion, and that a 200-μg dose of GnRH can increase LH secretion in either a high- or a low-P4 environment.

GnRH dose reduction decreases pituitary LH release and ovulatory response but does not affect corpus luteum (CL) development and function in llamas

Gonadotrophin releasing hormone (GnRH) is commonly used in llamas to induce ovulation; however, the consequence of reduced doses of GnRH on luteinizing hormone (LH) release, ovulatory response, and subsequent corpus luteum (CL) development and function have apparently not been investigated. Hence, we examined the effect of gradual reduction of gonadorelin acetate (GnRH) dosage on pituitary LH release, ovulatory response, CL development, and plasma progesterone concentrations in llamas. Non-pregnant, non-lactating adult llamas were examined once daily by transrectal ultrasonography, and those with a follicle ≥8 mm in diameter that had grown for three consecutive days were randomly assigned to receive 50 (GnRH50, n = 23), 25 (GnRH25, n = 29), 12.5 (GnRH12.5, n = 29), or 6.25 μg (GnRH6.25, n = 29) of GnRH, or 0.5 mL of PBS (Control group, n = 16) im. In a subset (7 or 8 animals/group), intense blood sampling was done to measure LH concentrations. All females were examined by ultrasonography every 12 h from treatment (Day 0) to Day 2 to determinate ovulation, and thereafter on alternate days until Day 16 to evaluate CL development (9–13 animals/group). Also, blood samples for progesterone determination were taken (9 or 10 animals/group) on alternate days from Days 0–16. Ovulatory response (%) was highest (P < 0.05) in the GnRH50 (82.6), intermediate in the GnRH25 (72.3) and GnRH12.5 (75.9) groups, and lowest in the GnRH6.25 group (48.3). No ovulations were detected in the Control group. Mean peak LH concentrations (ng/mL) were highest (P < 0.05) for GnRH50 (6.2), intermediate for GnRH25 (4.4) and GnRH12.5 (2.9), and lowest for GnRH6.25 (2.2) groups. In addition, based on regression analysis, llamas with an LH peak <4 ng/mL were less likely to ovulate. Llamas given 50 μg of GnRH released more (P < 0.05) pituitary LH and had an LH surge of longer duration than those given 25, 12.5, or 6.25 μg. However, in those that ovulated, neither GnRH treatment nor treatment by time interaction affected (P > 0.05) CL diameter or plasma progesterone concentrations. In summary, reducing the dose of GnRH gradually decreased the magnitude of the preovulatory LH surge and ovulatory response; however, subsequent CL development and plasma progesterone concentrations were not affected.

Characterization of Seasonal Variations in Responsiveness of Pituitary Gland to Different Doses of Gonadotropin Releasing Hormone in Buffalo Cows

In tropical countries such as India, it has been observed that a number of buffalo cows experience seasonal anestrous during summer months. This might be due to seasonal changes in responsiveness of pituitary gland to gonadotropin releasing hormone (GnRH) and/or decreased hypothalamic GnRH release. Attempts were made to characterize the responsiveness of pituitary gland to a range of doses (0.1, 1, 3, 10 and 33 µg) of GnRH in terms of LH and progesterone (P4) secretions during summer (April-May) and rainy (September-November) months. As a part of these studies, a radioimmunoassay method for estimation of circulating LH in buffalo cows was standardized. During summer months, it was observed that in the presence of low circulating P4 levels the minimum dose of GnRH required for eliciting a significant increase in circulating LH levels was 10 μg/animal that corresponded to a dose of ~28 ng/kg BW. However, during rainy months, administration of the same dose of GnRH failed to elicit a response suggesting that the pituitary gland is not responsive to low doses of exogenous GnRH. On the other hand, buffalo cows receiving a dose of 100 µg of GnRH during rainy months elicited a surge-like increase in circulating LH that peaked at 2 h and the increase in LH concentrations lasted for nearly 6 h post GnRH treatment. The results appear to suggest that during summer months the pituitary gland function is not affected, but there may be lowered hypothalamic GnRH input to the pituitary gland.

Teasing apart socially‐induced infertility in non‐reproductive female Damaraland mole‐rats, Fukomys damarensis (Rodentia: Bathyergidae)

The Damaraland mole-rat is a subterranean mammal exhibiting extreme reproductive skew with a single reproductive female in each colony responsible for procreation. Non-reproductive female colony members are physiologically suppressed while in the colony, exhibiting reduced concentrations of plasma luteinizing hormone (LH) and a decreased response of the pituitary, as measured by the release of bioactive LH, to an exogenous dose of gonadotrophin releasing hormone (GnRH). Removal of the reproductive female from the colony results in an elevation of LH and an enhanced response of the pituitary to a GnRH challenge in non-reproductive females comparable to reproductive females, implying control of reproduction in these individuals by the reproductive female. The Damaraland mole-rat is an ideal model for investigating the physiological and behavioral mechanisms that regulate the hypothalamo-pituitary-gonadal axis. In contrast, we know less about the control of reproduction at the level of the hypothalamus. The immunohistochemistry of the GnRH system of both reproductive and non-reproductive female Damaraland mole-rats has revealed no significant differences with respect to morphology, distribution or numbers of immunoreactive GnRH perikarya. We examined whether the endogenous opioid peptide beta-endorphin was responsible for the inhibition of the release of the GnRH from the neurons indirectly by measuring LH concentrations in these non-reproductive females following single, hourly and 8 hourly injections of the opioid antagonist naloxone. The results imply that the endogenous opioid peptide, beta-endorphin, is not responsible for the inhibition of GnRH release from the perikarya in non-reproductive females. Preliminary data examining the circulating levels of cortisol also do not support a role for circulating glucocorticoids. The possible role of kisspeptin is discussed.

Timing of androgen deprivation therapy use and fracture risk among elderly men with prostate cancer in the United States

Fractures are a recognized consequence of androgen deprivation therapy (ADT); however, less is known about the incidence of fracture in relation to the timing of ADT use or the impact of fracture on mortality in men with prostate cancer. Using data from the Surveillance, Epidemiology, and End Results-Medicare linked database, we estimated adjusted hazard ratios (aHRs) using time-dependent Cox regression for fracture incidence related to the recency of exposure and dose among prostate cancer patients on gonadotropin-releasing hormone (GnRH) agonists, as well as mortality associated with fractures. In our cohort of 80 844 patients, ADT was associated with an increased rate of fracture in both non-metastatic patients (aHR = 1.34; 95% confidence interval [CI] = 1.29-1.39) and metastatic patients (aHR = 1.51; 95%CI = 1.36-1.67). Fracture rates increased with increasing cumulative GnRH dose but decreased with increasing number of months since last use in each dose category. The mortality rate doubled for men experiencing a fracture after their diagnosis compared with that for men who did not experience a fracture (aHR = 2.05; 95%CI = 1.98-2.12). ADT in elderly men with prostate cancer increased the incidence of fractures, and the effect appears to diminish with increasing time since the last dose of a GnRH agonist. Experiencing a fracture after the diagnosis of prostate cancer was associated with decreased survival.

High-dose recombinant LH add-back strategy using high-dose GnRH antagonist is an innovative protocol compared with standard GnRH antagonist

High daily doses of gonadotrophin-releasing hormone (GnRH) antagonists during the follicular phase of ovarian stimulation were associated with low implantation rates. To test if this occurred because of profound pituitary suppression, the pituitary response was suppressed with a high-dose GnRH antagonist and recombinant LH (rLH) was added back to correct the implantation rate. An open-label, randomized, controlled, prospective clinical study in 60 patients undergoing IVF was performed. GnRH antagonist was initiated on day 6 of stimulation (2 mg/day) together with 375 IU rLH, and maintained until the day of HCG administration. Controls received 0.25 mg/day GnRH antagonist. Fluctuating LH concentrations were present on days 3 and 6 in both groups. This strong fluctuation continued on day 8 and on the day of HCG administration in the control (low-dose) group, where 30% of patients had LH concentrations <1 IU/1 on the HCG day. The study (high-dose) group showed stable LH concentrations on day 8 and on the HCG day, with no LH surges. No clinical differences were found between groups. The LH add-back strategy (375 IU/day) rescued the adverse effects that high doses of GnRH imposed on implantation. These results suggest that rLH should be considered during ovarian stimulation with GnRH antagonist.

Evaluation of the 5- vs. 7-day CIDR program in dairyheifers before timed artificial insemination (2011)

Our objectives were to determine: (1) the effectiveness of an injection of PGF2α to regress the corpus luteum before initiating an timed artificial insemination (TAI) program, (2) ovulation response to gonadotropin-releasing hormone (GnRH), and (3) pregnancy outcomes in dairy heifers inseminated with conventional and gender-biased semen. Heifers (n = 545) from 3 locations (Florida, Kansas, and Mississippi) were assigned randomly to 1 of 2 treatments: (1) 25-mg prostaglandin F2α (PGF2α) injection and controlled internal drug release (CIDR) insert on day −7 followed by 100 μg of GnRH administered on day −5, and a 25-mg PGF2α injection at CIDR insert removal (7D) on day 0; or (2) 100 μg of GnRH and insertion of previously used autoclaved CIDR on day −5 and a 25-mg PGF2α injection at CIDR removal (5D) on day 0. Artificial insemination occurred after detected estrus from days 0 to 3. Those heifers not detected in estrus were inseminated on day 3 (72 hours after PGF2α) and given a second 100-μg dose of GnRH (72 hours after CIDR removal). Blood collected on days −7 and −5 was assayed to determine concentrations of progesterone and presence of a CL (progesterone ≥1 ng/mL) on d −7. Blood progesterone concentrations on days 0 and 3 were used to determine if luteolysis occurred in all heifers. Pregnancy was determined on days 32 and 60 and intervening pregnancy loss was calculated. Of those heifers in the 7D treatment having progesterone ≥1 ng/mL on day −7, the proportion having progesterone <1 ng/mL 2 days later (luteolysis) was greater (P < 0.05) than that in the 5D treatment (43.0 vs. 22.9%), respectively. A treatment by location interaction was detected for pregnancies per AI. The Kansas location had no detectable treatment differences. In contrast, the 7D treatment produced more (P < 0.05) pregnancies in the first replicate of the Florida location and at the Mississippi location. We concluded that the 5D protocol was not more effective in producing acceptable luteolysis, pregnancy, and ovulation rates compared with the modified 7D protocol.

Abstract B11: Risk of fracture and androgen deprivation therapy

Abstract Background: Extended use of androgen deprivation therapy (ADT) is common among elderly men; however, the associated long-term toxic effects have not been well documented. Methods: We conducted a population based cohort study by analyzing a total of 46,587 men diagnosed with localized prostate cancer and survived at least 5 years after diagnosis in the Surveillance, Epidemiology, and End Results (SEER) -Medicare program to estimate the risk of fracture among men who received long-term ADT. Results: More than 46% of ADT users received more than 25 months of treatment. The hazard ratio (HR) of hospitalized fracture was 1.47 (95 percent confidence interval, 1.29 to 1.67) among men receiving 36 or more doses of Gonadotropin-releasing hormone (Gn-RH) agonist. Men treated with ADT were associated with a 57.8% increase in the risk of multiple fractures after the first 24 months of treatment. Older age, higher comorbidity, history of fracture and stoke were independently associated with increased fracture risk. Men who were 75 years of age or older and received GnRH agonist for more than 24 months were associated with a 3.63 times risk of having fracture, compared with those aged 66 to 74 and have ADT shorter than 24 months. Conclusion: Men who are older and with comorbidity are more likely to received long-term ADT than attempted curative treatment. However, those men are also at substantial risk of fracture. The increased risk of fracture along with ADT should be carefully evaluated before initiating a treatment. Citation Information: Cancer Prev Res 2010;3(12 Suppl):B11.

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

Previous animal and human studies using low-dose estrogen have demonstrated estrogen negative feedback on gonadotropin secretion through gonadotropin-releasing hormone (GnRH) release at the level of the hypothalamus in women. Whether low-dose estrogen also exerts a direct negative feedback at the level of the pituitary is unclear due to insufficient data. In a recent study, a decrease was found in pituitary responsiveness to GnRH with aging in women. Studies in human beings aimed to establish a direct pituitary site of estrogen negative feedback and investigate the interaction of estrogen, and aging in the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) feedback loop have been hampered by the inability thus far to isolate the pituitary response from endogenous hypothalamic input. This study tested the hypothesis that estrogen has a direct negative feedback effect at the pituitary and also investigated whether this effect would vary with aging. Isolation of pituitary responsiveness from hypothalamic and ovarian input was achieved through blockade of the GnRH receptor using the NAL-GLU GnRH antagonist, followed by graded doses of GnRH before and after 1 month of estrogen administration. The participants were healthy postmenopausal women aged 48 to 56 years (n = 8) or 70 to 75 years (n = 8). After estrogen administration, there was a significant decrease in the LH (P = 0.01) and FSH (P = 0.0001) responses to GnRH in all study subjects. There was also a decrease in the ratio of FSH to LH amplitudes in response to GnRH (P = 0.04). The inhibitory effect of estrogen on FSH responses was significantly diminished with aging (P = 0.02). In contrast to FSH, LH responses were not significantly affected by aging (P = 0.4). These findings demonstrate that estrogen has a direct inhibitory effect on pituitary responsiveness to GnRH in women. This estrogen negative feedback diminishes with aging. FSH but not LH responses are inhibited by estrogen.

Signaling Responses to Pulsatile Gonadotropin-releasing Hormone in LβT2 Gonadotrope Cells

The hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH) is secreted in a pulsatile fashion by hypothalamic neurons, and alterations in pulse frequency and amplitude differentially regulate gonadotropin synthesis and release. In this study, we investigated the kinetics of G(s) and G(q) signaling in response to continuous or pulsatile GnRH using fluorescence resonance energy transfer reporters in live mouse LbetaT2 gonadotrope cells. cAMP and protein kinase A-dependent reporters showed a rapid but transient increase in fluorescence resonance energy transfer signal with increasing doses of constant GnRH, and in contrast diacylglycerol (DAG) and calcium reporters showed a rapid and sustained signal. Multiple pulses of GnRH caused multiple pulses of cAMP and protein kinase A activation without desensitization, but the DAG and calcium reporters were rapidly desensitized resulting in inhibition of calcium and DAG responses. At the transcriptional level, both a cAMP-dependent cAMP-response element reporter and a DAG/calcium-dependent AP-1 reporter showed a pulse frequency-dependent increase in luciferase activity. However, constant GnRH stimulation gave very little cAMP-response element activation but very strong AP-1 activation. Based on these data, we propose that both the GnRH-R-G(s) and G(q) pathways are responsive to pulses of GnRH, but only the G(q) pathway is responsive to constant GnRH. Furthermore, the G(q) pathway is subject to desensitization with multiple GnRH pulses, but the G(s) pathway is not.

Progesterone concentration, estradiol pretreatment, and dose of gonadotropin-releasing hormone affect gonadotropin-releasing hormone-mediated luteinizing hormone release in beef heifers

We examined whether progesterone (P 4)-induced suppression of LH release in cattle can be overcome by an increased dose of exogenous gonadotropin-releasing hormone (GnRH) or pretreatment with estradiol (E 2). In Experiment 1, postpubertal Angus-cross heifers (N = 32) had their 2 largest ovarian follicles ablated 5 d after ovulation. Concurrently, these heifers were all given a once-used, intravaginal P 4-releasing insert (CIDR), and they were randomly assigned to be given either prostaglandin F 2α (Low-P 4) or no treatment (High-P 4) at follicle ablation, and 12 h later. Six days after emergence of a new follicular wave, half of the heifers in each group (n = 8) were given either 100 or 200 μg of GnRH i.m. Plasma luteinizing hormone (LH) concentrations were higher in the Low- vs High-P 4 groups, and in heifers given 200 vs 100 μg of GnRH (mean ± SEM 15.4 ± 2.2 vs 9.1 ± 1.2, and 14.8 ± 2.1 vs 9.8 ± 1.4 ng/mL, respectively; P ≤ 0.01). Ovulation rate was higher ( P = 0.002) in the Low-P 4 group (15/16) than in the High-P 4 group (6/16), but it was not affected by GnRH dose ( P = 0.4). In Experiment 2, heifers (n = 22) were treated similarly, except that 5.5 d after wave emergence, half of the heifers in each group were further allocated to be given either 0.25 mg estradiol benzoate i.m. or no treatment, and 8 h later, all heifers were given 100 μg GnRH i.m. Both groups treated with E 2 (Low- and High-P 4) and the Low-P 4 group without E 2 had higher peak plasma LH concentrations compared to the group with high P 4 without E 2 (12.6 ± 1.8, 10.4 ± 1.8, 8.7 ± 1.3, and 3.9 ± 1.2 ng/mL, respectively; ( P < 0.04)). However, E 2 pretreatment did not increase ovulation rates in response to GnRH ( P = 0.6). In summary, the hypotheses that higher doses of GnRH will be more efficacious in inducing LH release and that exogenous E 2 will increase LH release following treatment with GnRH were supported, but neither significantly increased ovulation rate.

Double GnRH-antagonist dose before HCG administration may prevent OHSS in oocyte-donor cycles: a pilot study

This pilot study evaluated the possibility of preventing early ovarian hyperstimulation syndrome (OHSS) by increasing the daily dose of gonadotrophin-releasing hormone (GnRH) antagonist administration (to twice a day) in oocyte-donor cycles stimulated with the antagonist protocol. The study included 72 oocyte donors who underwent ovarian stimulation using the GnRH antagonist protocol and might have had their cycle cancelled because of ovarian hyper-response. All women were donors presenting a rapid rise of oestradiol > or = 3000 pg/ml early in the stimulation period with more than 15 follicles of < or = 15 mm in diameter. By decreasing the rFSH dose to 75 IU a day with an additional daily dose of GnRH antagonist (0.25 mg twice a day), the oestradiol concentrations were lowered or reached a plateau before human chorionic gonadotrophin was given. A marked decrease in oestradiol concentrations and ovarian volume was observed on the day of oocyte retrieval and 3 days post retrieval. None of the donors needed coasting, were cancelled or developed OHSS. In over-responding oocyte donors, by increasing the usual GnRH-antagonist dose to twice a day during ovarian stimulation, the oestradiol rise can be blocked while a minimal follicular stimulation may continue without the risk of developing OHSS or affecting the outcome.

Is Doublesynch protocol a new alternative for timed artificial insemination in anestrous dairy cows

This is the very first report that suggests high pregnancy rates can be obtained with use of the Doublesynch protocol in anestrous dairy cows. Recently, a new synchronization method has been developed (Doublesynch) that resulted in synchronized ovulations both after the first and second gonadotropin-releasing hormone (GnRH) treatments. It was suggested that this protocol has the potential to increase the pregnancy rates in primiparous dairy cows. The aim of the current study was to confirm the success of the Doublesynch protocol and further to investigate the effect of this method on pregnancy rates in anestrous cows. Lactating primiparous Holstein (Bos taurus) cows (n = 165) between 60 and 172 d postpartum were monitored twice with 10-d intervals (on Days –10 and 0) by ultrasonography, and blood samples were collected. Cows were classified as anestrous if both blood samples had progesterone (P4) concentration <1 ng/mL and as cyclic if at least one of the two samples had P4 concentration ≥1 ng/mL. Cyclic cows were classified again as cyclic-high P4 (having an active corpus luteum) if the second blood samples had P4 concentrations ≥1 ng/mL and as cyclic-low P4 if P4 concentrations were <1 ng/mL on Day 0. Then, the cows classified as anestrous (n = 51), cyclic-high P4 (n = 63), or cyclic-low P4 (n = 51) were put into two treatment groups (Ovsynch or Doublesynch) randomly to establish six groups. Cows in the Ovsynch group were administered a GnRH (lecirelin 50 μg, im) on Day 0, PGF (Prostaglandin F2 alpha, D-cloprostenol 0.150 mg, im) on Day 7, and a second dose of GnRH 48 h later. Cows in the Doublesynch group were administered a PGF on Day 0, GnRH on Day 2, a second PGF on Day 9, and a second GnRH on Day 11. Timed artificial insemination (TAI) was performed 16 to 20 h after the second GnRH in both treatment groups. Pregnancy diagnosis was conducted (by ultrasonography) 45 ± 5 d after TAI. In anestrous cows and those with high and low progesterone concentration at treatment onset, Doublesynch treatment led to markedly increased pregnancy rates with respect to Ovsynch treatment (P < 0.05). On the overall analysis of data, it was revealed that the Doublesynch method increased pregnancy rates by 43 percentage units (29.8% vs. 72.8%, P < 0.0001) in relation to Ovsynch. Pregnancy rates of cows having small, medium, or large follicles at the day of second GnRH administration were similar in the Doublesynch group (70.4%, 85.2%, and 63.0%, respectively; P > 0.05), whereas pregnancy rates reduced dramatically as follicle size increased in the Ovsynch group, particularly in cows with follicles greater than 16 mm (45.5%, 28.1%, and 5.3%, respectively; P < 0.05). Our results confirm and support observations that the Doublesynch protocol increases the pregnancy rates in postpartum primiparous cows as reported previously. Our data also demonstrate that the Doublesynch method increases the pregnancy rates in anestrous cows. Thus, these data suggest that the Doublesynch protocol can be used to obtain satisfactory pregnancy rates after TAI in both anestrous and cycling primiparous dairy cows regardless of stage of estrous cycle.

Progesterone treatment, FSH plus eCG, GnRH administration, and Day 0 Protocol for MOET programs in sheep

The effect of various superstimulatory treatments on the number of corpora lutea, fertilization rate, and embryo yield was studied in sheep. Overall, data from 708 Merino donors and 4262 embryos were analyzed in four experiments. In Experiment 1, varying intervals of progesterone treatment (5 to 14 d) before follicle-stimulating hormone (FSH) administration did not significantly affect the proportion of responding donors, the mean number of corpora lutea, or the mean number of recovered and transferable embryos per donor. In Experiment 2, a single dose of equine chorionic gonadotropin (eCG, 200 or 300 IU) combined with the FSH treatment (i.e., given at CIDR removal) reduced the number and the quality of embryos compared with that for not giving eCG (P < 0.05). In Experiment 3, one dose of gonadotropin-releasing hormone (GnRH) given 24 h after CIDR removal improved the number of transferable embryos compared with that for not giving GnRH (P < 0.05). In Experiment 4, the new superstimulatory Day 0 Protocol, which includes starting FSH treatment at the emergence of Wave 1 (i.e., soon after ovulation, in the absence of a large follicle), improved ovarian response, with a tendency to produce more embryos compared with that for the Traditional Protocol. In summary, this study, analyzing data from various pharmacologic treatments, allows an improvement from four to eight transferable embryos per treated donor in multiple ovulation and embryo transfer programs in sheep.

Multifunctional angiogenic factors: add GnRH to the list. Focus on “Gonadotropin-releasing hormone-regulated chemokine expression in human placentation”

the historical view that angiogenesis is governed by the action of a few dominant trophic factors, such as VEGF, FGF, and transforming growth factor-β (TGF-β), has steadily eroded over the past two decades to give rise to the vision of a much more dynamic regulation in which angiogenesis is

Plasma luteinizing hormone concentrations in cows given repeated treatments or three different doses of gonadotropin releasing hormone

We hypothesized that: (i) repeated GnRH treatments would increase the magnitude and duration of the LH surge and would increase progesterone (P4) concentrations after ovulation; and (ii) the release of pituitary LH would be greater in response to larger doses of GnRH. In Experiment 1, ovary-intact cows were given an intravaginal P4 (1.9 g) insert (CIDR) for 10 d and 500 μg cloprostenol (PGF) at CIDR removal to synchronize estrus. On Days 7 or 8 after estrus, cows received two PGF treatments (12 h apart) and 100 μg GnRH at 36 (Control), 36 and 38 (GnRH38), or 36 and 40 h (GnRH40) after the first PGF. Mean plasma LH concentration (ng/mL) was greater ( P < 0.05) in GnRH38 (8.8 ± 1.1) than in Control (5.1 ± 1.3), with that in GnRH40 (5.8 ± 1.3) being intermediate. Although the duration (h) of the LH surge was longer in GnRH40 (8.0 ± 0.4) than in either GnRH38 ( P < 0.05; 7.0 ± 0.3) or Control ( P < 0.09; 7.1 ± 0.4), mean postovulatory P4 (ng/mL) was greater ( P < 0.01) in Control (4.2 ± 0.7) than in GnRH38 (2.9 ± 0.6) or GnRH40 (3.0 ± 0.7) cows. In Experiment 2, ovariectomized cows were given a CIDR for 10 d and 2 mg of estradiol cypionate im at CIDR insertion. Thirty-six hours after CIDR removal, cows received, 50, 100, or 250 μg of GnRH. Cows given 250 μg GnRH released more LH (9.4 ± 1.4 ng/mL) than those given 50 or 100 μg (6.1 ± 1.3 and 5.4 ± 1.4 ng/mL, respectively), and had an LH surge of longer duration than those given 50 μg (6.8 ± 0.4 vs. 5.1 ± 0.3 h). In summary, ovary-intact cows in the GnRH38 group had greater mean and peak LH concentrations, but subsequent plasma P4 concentrations were lower than in Control cows. Ovariectomized cows given 250 μg GnRH had a greater pituitary release of LH.

New Derivatives of GnRH as Potential Anticancer Therapeutic Agents

GnRH (gonadotropin-releasing hormone), a decapeptide produced by the hypothalamus, plays an important role in the reproduction by regulating the pituitary-gonadal axis. Continuous high doses of GnRH or its superactive agonists result in desensitization of the pituitary gonadotropes and a suppression of sex steroid production by the gonads (chemical castration). Based on these effects, the treatment with GnRH agonists has become a widely used hormonal therapy of the sex-steroid dependent tumors. It was also demonstrated that most tumor cells contain GnRH receptors, and the direct antiproliferative effect of GnRH analogs on cancer cells might be mediated by these receptors. Development of new GnRH derivatives is focused on the decrease of their hormonal potency resulting in higher selectivity of the antitumor activity. One of the most promising natural GnRH analogs, lamprey (l) lGnRH-III, was isolated from see lamprey. This variant of GnRH binds to GnRH receptors and inhibits proliferation of various cancer cells. However, its endocrine effect is insignificant in mammals. lGnRH-III dimers and conjugates were prepared and were shown to have increased antiproliferative effects on various cancer cells, while their hormonal activity was lower than that of the native hormone. lGnRH-III was applied as targeting moiety to deliver anticancer agents to tumor cells. Research data concerning lGnRH-III and its analogs represent a new outlook for research trends of the application of GnRH compounds in cancer chemotherapy. Studies on the effects of lGnRH-III derivatives including antiproliferative effects, cytotoxicity, hormonal actions, and enzymatic stability are reviewed in this article.

Poor responder protocols for in-vitro fertilization: options and results

To present the options and the results in the management of poor responders in in-vitro fertilization. There is no controlled ovarian hyperstimulation protocol which is best suited for all poor responders. Low dose gonadotropin-releasing hormone agonist regimes appear to be most advantageous. Prediction of compromised response prior to cycle initiation by a thorough assessment of ovarian reserve as well as a careful review of past responses could allow for a more appropriate selection of a controlled ovarian hyperstimulation protocol for each individual patient. Optimistic data have been presented by the use of high doses of gonadotropins, flare up gonadotropin-releasing hormone agonist protocols (standard or microdose), stop protocols, luteal onset of gonadotropin-releasing hormone agonist, and short protocols. Natural cycle also seems to be an appropriate strategy to be considered. There is no universal definition for the 'poor responder'. Numerous strategies have been proposed to improve ovarian stimulation in poor responders, but none of them is the ideal for all such patients. More data from good quality controlled trials are needed.

Microdose gonadotropin-releasing hormone agonist flare-up protocol versus multiple dose gonadotropin-releasing hormone antagonist protocol in poor responders undergoing intracytoplasmic sperm injection–embryo transfer cycle

To compare the efficacy of microdose GnRH agonist (GnRH-a) flare-up and multiple dose GnRH antagonist protocols in patients who have a poor response to a long luteal GnRH-a protocol. Prospective, randomized, clinical study. University hospital. Forty-two poor responder patients undergoing intracytoplasmic sperm injection (ICSI)-embryo transfer cycle. Twenty-one patients received microdose leuprolide acetate (LA) (50 microg twice daily) starting on the second day of withdrawal bleeding. The other 21 patients received 0.25 mg of cetrorelix daily when the leading follicle reached 14 mm in diameter. Serum E(2) levels, number of growing follicles and mature oocytes, embryo quality, dose of gonadotropin used, cancellation, fertilization, implantation rate and pregnancy rate (PR). The mean serum E(2) concentration on the day of hCG administration was significantly higher in the microdose GnRH-a group than in the GnRH antagonist group (1,904 vs. 1,362 pg/mL). The clinical PRs per started cycle of microdose GnRH-a and GnRH antagonist groups were 14.2% and 9.5%, respectively. There were no statistically significant differences in the other ovulation induction characteristics, fertilization and implantation rates. Microdose GnRH-a flare-up protocol and multiple dose GnRH antagonist protocol seem to have similar efficacy in improving treatment outcomes of poor responder patients.

Effect of season on luteal activity during the post partum period of dairy cows in temperate areas

Seasonal effects on luteal activity during post partum were evaluated in two consecutive studies in 253 dairy cows in Northern Italy. In study 1, plasma progesterone concentrations were determined on days 14, 21, 28, 35, 42, 49 and 56 post partum and in study 2 cows were synchronized and inseminated at a fixed time using two regimes based on the ‘Ovsynch’ protocol. Study 1: Animals were classified as luteal (progesterone >1.5 ng/ml in at least two consecutive samples) or non-luteal (progesterone <1.5 ng/ml in all samples). The proportion of cows without luteal activity from calving to day 56 post partum was 47/253 (18.5%). Of the 47 cows without luteal activity, 42 (89%) were detected during the warm months of the year and five were detected during the cold months of the year, and the effect of season was highly significant (P < 0.001). Study 2: Three study groups were established; control (CONT, untreated cows, n = 92), GPG (cows receiving gonadotropin-releasing hormone (GnRH) on day 0, PGF2α on day 7 followed by a second dose of GnRH 24 h later, n = 80); and HPH (the same as the GPG group, but with human chorionic gonadotropin (hCG) substituted for GnRH, n = 81). In the GPG and HPH groups, cows were inseminated 16 to 22 h after the second GnRH or hCG injection. Untreated cows were inseminated at first estrus after a voluntary weaning period. Because the effects of the GPG and HPH regimes on pregnancy rate were not significantly different, data were pooled into a single treatment group (TREAT). Pregnancy rates during the warm months of the year were 16% and 15% at first service and 65% and 66% at day 135 post partum for CONT and TREAT groups, respectively. Pregnancy rates during the cold months of the year were 36% and 38% at first service and 72% and 76% at day 135 post partum for CONT and TREAT groups, respectively. There was an effect of season (P < 0.05) but not of treatment on pregnancy rate. Treatment reduced the number of days from calving to conception during both the cold (101 ± 3.2 v. 121 ± 3.1 days; P < 0.001) and warm seasons (122 ± 3.2 v. 145 ± 3.1 days; P < 0.001). In conclusion, the present study shows that (i) heat stress during the warm season can compromise luteal activity and (ii) that regimes based on the Ovsynch protocol did not improve pregnancy rate at first service or by 135 post partum, but they had a positive effect on the calving-to-conception interval.