Mean Luteinizing Hormone Research Articles

Hormonal Characteristics in the Early Luteal Phase of Conceptive and Nonconceptive Menstrual Cycles

To determine whether serum hormone profiles are different in nonconceptive and conceptive menstrual cycles after ovulation and before implantation. Daily blood samples obtained during the luteal phase of nonconceptive cycles (n = 31) and conceptive cycles (n = 19) were analyzed (intersubject comparison). Samples obtained in sequential nonconceptive and conceptive cycles from five subjects (intrasubject comparisons) were analyzed to confirm results obtained with intersubject analysis. Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E(2)), progesterone, and relaxin were measured by immunoassay. A cell-based bioassay was used to determine whether the measurement of serum immunoreactive LH is a result of cross-reaction with human chorionic gonadotropin (hCG). Intersubject analysis showed that mean serum LH levels were significantly higher in conceptive cycles on day 4 and day 5 after the FSH peak in urine, and this was confirmed by intrasubject analysis. The addition of antibodies that precipitate hCG did not affect the activity of LH receptor ligand molecules in serum samples collected during the early luteal phase of conceptive cycles, as measured by bioassay. In contrast, this LH receptor binding activity was completely removed when precipitating antibodies for LH were added. The mean levels of serum E(2) were higher in conceptive cycles after day 4 following the FSH peak in urine. The mean values of serum FSH, progesterone, and relaxin were not significantly different in nonconceptive and conceptive cycles during the same time interval. The differences in luteal phase hormones may reflect alterations in signaling in the hypothalamic-pituitary-ovarian axis that begin during the preovulatory period of nonconceptive cycles.

Suppression of pulsatile luteinizing hormone secretion but not luteinizing hormone surge in leptin resistant obese Zucker rats.

The adipose tissue-derived hormone leptin may be a primary mediator linking nutritional status and reproduction. The present study used the leptin-resistant obese female Zucker rat to investigate whether leptin signalling is required for normal pulsatile luteinizing hormone (LH) secretion and/or generation of the LH surge. For the pulsatile LH secretion study, an indwelling atrial catheter was implanted and a low dose of oestrogen given as a subcutaneous implant to lean and obese ovariectomized (OVX) Zucker rats. One week following OVX, blood samples were collected every 10 min for 3 h during the morning. Plasma LH concentrations were measured by radioimmunoassay. For the LH surge study, lean and obese OVX rats were given a high dose of oestrogen as a subcutaneous implant. Two days later, rats were given progesterone at 09.00 h to induce a proestrus-like LH surge. Blood samples were collected from an indwelling atrial catheter throughout that and the following day and plasma LH concentrations were measured by radioimmunoassay. LH pulse amplitude and mean LH secretion were profoundly attenuated in obese Zucker rats compared with lean littermates, whereas LH pulse frequency was not significantly different between phenotypes. The opioid receptor antagonist naloxone did not affect the pattern of pulsatile LH secretion in obese rats, suggesting that leptin does not exert its facilitatory effects on LH secretion through an opioidergic pathway. Both lean and obese rats showed characteristic steroid-induced LH surges. It therefore appears that a leptin signal is required for generation of a normal pattern of pulsatile LH secretion, but is not a necessary component of the steroid-induced LH surge.

Phosphodiesterase expression targeted to gonadotropin-releasing hormone neurons inhibits luteinizing hormone pulses in transgenic rats.

Experiments in the GT1 gonadotropin-releasing hormone (GnRH) cell line have shown that the cAMP signaling pathway plays a central role in regulating the excitability of the cells. Lowering cAMP levels by expressing the constitutively active cAMP-specific phosphodiesterase PDE4D1 in GT1 cells inhibited spontaneous Ca2+ oscillations and intrinsic pulsatile GnRH secretion. To address the role of cAMP levels in endogenous GnRH neurons, we genetically targeted expression of PDE4D1 (P) to GnRH neurons in transgenic rats (R) by using the GnRH gene promoterenhancer regions (G). Three lines of transgenic rats, GPR-2, -4, and -5, were established. In situ hybridization and RT-PCR studies demonstrated that transgene expression was specifically targeted to GnRH neurons. Decreased fertility was observed in female but not in male rats from all three lines. The mean luteinizing hormone (LH) levels in ovariectomized rats were significantly reduced in the GPR-4 and -5 lines but not in the GPR-2 line. In castrated male and female GPR-4 rats, the LH pulse frequency was dramatically reduced. Six of twelve GPR-4 females studied did not ovulate and had polycystic ovaries. The remaining six females ovulated, but the magnitude of the preovulatory LH surge was inhibited by 63%. These findings support the hypothesis that cAMP signaling may play a central role in regulating excitability of GnRH neurons in vivo. The GPR-4 line of transgenic rats provides a genetic model for the understanding of the role of pulsatile gonadotropin release in follicular development.

A six-month, open-label study assessing a new formulation of leuprolide 7.5 mg for suppression of testosterone in patients with prostate cancer

Objective: The safety, efficacy, and pharmacokinetics of monthly subcutaneous injections of a new leuprolide acetate (LA) depot formulation were investigated in patients with advanced prostate cancer. Methods: The 2-part, 6-month (168-day), open-label, multicenter study enrolled male patients diagnosed with adenocarcinoma of the prostate (Jewett stage C or D). LA-2500 7.5-mg (a new subcutaneous depot formulation containing 7.5 mg of LA) injections were administered at monthly (28-day) intervals. The primary efficacy parameter was total serum testosterone level. A breakthrough response was defined as a single testosterone measurement >50 ng/dL after achieving castration testosterone levels. Testosterone was isolated from sera by alumina column chromatography and measured by radioimmunoassay (RIA). LA was purified by solid-phase extraction and high-performance liquid chromatography and was then quantitated by RIA. Results: One hundred seventeen of the 120 enrolled patients completed the 6-month study. Three patients withdrew for reasons not related to treatment. LA had a mean (SD) maximal concentration of 26.3 (12.6) ng/mL at 4.66 (1.44) hours and was detected for a mean of 37 days (range, 28–49 days). By day 28, 94.1% (112/119) of the patients achieved medical castration (serum testosterone ≤50 ng/dL). By day 42, 100.0% (118/118) of the patients remaining in the study had serum testosterone levels ≤50 ng/dL and 97.5% (115/118) had levels ≤20 ng/dL. At study completion, the mean (SD) serum testosterone level was 6.12 (4.3) ng/dL (range, 3.0–27.0 ng/dL). No breakthrough or acute-on-chronic responses were reported throughout the study. From baseline to month 6, mean (SD) luteinizing hormone level decreased from 8.0 (7.3) mIU/mL to 0.09(0.1) mIU/mL, and mean (SD) prostate-specific antigen level decreased from 32.9 (86.3) ng/mL to 3.2 (12.0) ng/mL. Treatment-related adverse events were reported by 74.2% (89/120) of patients, the most common being hot flashes (56.7%). Conclusion: This 6-month, open-label, noncontrolled study showed LA-2500 7.5-mg depot was well tolerated and maintained testosterone suppression ( ≤50 ng/dL) in the patients completing the study without any testosterone breakthrough responses.

Luteinizing hormone and growth hormone secretion in ewes infused intracerebroventricularly with neuropeptide Y

Neuropeptide Y (NPY) provides an important hypothalamic link between nutritional status and neuroendocrine mechanisms regulating growth and reproduction. The objective of the following series of experiments was to determine the effects of single or continuous administration of NPY on secretion of luteinizing hormone (LH) and (or) growth hormone (GH). In experiment 1, four ovariectomized (OVX) ewes and four OVX+estrogen-treated ewes each received, in a 4×4 Latin Square arrangement of treatments, a single injection of 0, 0.5, 5, or 50 μg NPY via an intracerebroventricular (i.c.v.) cannulae to determine the effects on secretion of GH. NPY significantly elevated serum GH at the 50 μg dose regardless of estrogen exposure ( P=0.003). In experiment 2, eight OVX ewes were infused i.c.v. with NPY or saline ( n=4/trmt) continuously for 20 h in a linearly increasing dose, ending at 50 μg/h NPY. Blood samples were collected via jugular cannulae every 10 min during hour –4–0 (interval 1, pre-treatment), hour 6–10 (interval 2) and hour 16–20 (interval 3) relative to the initiation of infusion (0 h). Mean LH and LH pulse frequency were lower in NPY- versus saline-infused ewes during intervals 2 and 3 ( P<0.01), but NPY had no discernable effect on serum GH ( P>0.10). In experiment 3, four OVX ewes were continuously infused with NPY as in experiment 2, except that the maximum 50 μg/h dose was achieved after only 10 h of infusion. Blood samples were collected every 10 min, beginning 4 h before and continuing until 4 h after the NPY infusion. Mean serum LH changed significantly over time ( P=0.0001), decreasing below pre-treatment levels by hour 3 of NPY infusion ( P<0.01), and returning to pre-treatment concentrations following the end of infusion ( P>0.15). Serum GH also changed significantly over time ( P<0.001). Mean GH levels tended to be greater than pre-treatment levels by hour 2 of infusion ( P<0.08), but thereafter returned to basal levels. Serum GH also increased following the end of NPY infusion ( P<0.03). From these data we conclude that NPY exerts a persistent inhibitory effect on secretion of LH, and may stimulate the secretion of GH during the initiation and cessation of infusion of NPY. These observations support a role for NPY in mediating the effects of undernutrition on both LH and GH, and also provide evidence for potential mechanisms by which leptin, acting through NPY, may stimulate the secretion of GH.

A Clinical Study Of 22.5 mg. La-2550: A New Subcutaneous Depot Delivery System For Leuprolide Acetate For The Treatment Of Prostate Cancer

The safety, efficacy and pharmacokinetics of a unique 3-month subcutaneous depot of leuprolide acetate were investigated in patients with prostate cancer. This open label, noncomparative, 6-month multicenter study enrolled 117 patients diagnosed with adenocarcinoma of the prostate. LA-2550 (22.5 mg. depot) (Atrix Laboratories, Fort Collins, Colorado) was administered subcutaneously once every 3 months. The primary efficacy parameter was serum testosterone 50 ng./dl. or less. Pharmacokinetics were analyzed in a subset of 22 patients. Of the 117 enrolled patients 111 (98%) completed the 6-month study. Five patients withdrew for nontreatment related events and 1 was withdrawn because he received less than a full dose of the study drug. By day 28, 98% of patients had serum testosterone 50 ng./dl. or less and 84% had achieved 20 ng./dl. or less. By day 35 all patients had 50 ng./dl. or less testosterone. A patient with a breakthrough response after testosterone suppression on day 49 (112 ng./dl.) regained suppression (27 ng./dl.) 14 days after the second injection (day 98). At study completion all patients had 50 ng./dl. or less testosterone (mean plus or minus standard error of mean 10.1 +/- 0.07) and 104 of the 111 (94%) had 20 ng./dl. or less. From baseline to month 6 mean luteinizing hormone decreased from 9.2 +/- 1.1 to 0.08 +/- 0.01 mIU/ml. and mean prostate specific antigen decreased more than 98%. No flare reactions were observed and patient assessments of bone pain and urinary symptoms were unchanged. The most common treatment related adverse event was hot flashes, which were mild in 57% of cases, moderate in 12% and severe in 0%. LA-2550 (22.5 mg. depot) produced and maintained safe and effective suppression of serum testosterone to well below the medical castrate level of 50 ng./dl. or less.

The GABA(B) antagonist CGP 52432 attenuates the stimulatory effect of the GABA(B) agonist SKF 97541 on luteinizing hormone secretion in the male sheep.

The objectives of this study were to determine if the gamma-aminobutyric acid (GABA)(B) agonist, 3-aminopropyl (methyl) phosphinic acid (SKF97541), would increase luteinizing hormone (LH) secretion when infused by microdialysis into the medial basal hypothalamus (MBH) of the castrated ram, and to determine if the action of SKF97541 would be attenuated by co-infusion of the GABA(B) antagonist CGP52432. Initial experiments established that infusion of SKF alone, at concentrations as low as 5 microM, increased mean LH, LH pulse amplitude, and in some cases, pulse interval. In the last experiment, animals were treated with artificial cerebrospinal fluid (CSF) alone, SKF alone (30 microM), 3-[[(3, 4-dichlorophenol) methyl] amino] propyl] diethoxymethyl) phosphinic acid (CGP) alone (500 microM), or SKF plus CGP. SKF increased both mean LH and LH pulse amplitude as compared with CSF. CGP alone had no significant effect on LH, but it attenuated the effect of SKF on mean LH. These observations indicate that the stimulatory effects of GABA(B) agonists on LH pulse patterns are mediated through GABA(B) receptors and provide further evidence that GABA(B) receptors located in the MBH can regulate pulsatile GnRH-LH release.

Effects of Soy Consumption on Gonadotropin Secretion and Acute Pituitary Responses to Gonadotropin-Releasing Hormone in Women

Soy contains the isoflavone phytoestrogens, genistein and daidzein. These isoflavones are partial estrogen agonists in cell and animal models, but effects from dietary soy in humans are unclear. Experiments were conducted in pre- and postmenopausal women to examine whether dietary isoflavones from soy behave as estrogen agonists, antagonists or have no effect on the estrogen-sensitive pituitary. Pituitary sensitivity to gonadotropin-releasing hormone (GnRH), an estrogen-sensitive endpoint, was measured during GnRH challenge tests administered before, during and after dietary soy consumption. The response to an isoflavone-rich soy food diet was examined in five premenopausal and seven postmenopausal women using transdermal estrogen replacement therapy. Estrogen agonists suppress gonadotropin concentrations and enhance GnRH priming (enhanced gonadotropin secretion in response to repeated doses of GnRH), whereas antagonists elevate gonadotropin concentrations and have no effect on GnRH priming. Each subject consumed 50 g textured soy protein containing 60 mg total isoflavones daily for 10-14 d. Baseline estradiol concentrations were consistent among study periods. In both pre- and postmenopausal women, soy consumption did not affect mean baseline or peak luteinizing hormone (LH) concentrations, indicating a lack of estrogen-like effect at the level of the pituitary. However, in postmenopausal subjects, mean LH secretion decreased after discontinuing soy, suggesting a residual estrogenic effect. In one premenopausal woman, enhanced LH secretion was observed after soy treatment, suggesting there may be subpopulations of women who are highly sensitive to isoflavones.

Suppressive Action of Orexin A on Pulsatile Luteinizing Hormone Secretion Is Potentiated by a Low Dose of Estrogen in Ovariectomized Rats

Orexins are hypothalamic neuropeptides which stimulate luteinizing hormone (LH) secretion in estrogen- and progesterone-treated ovariectomized (OVX) rats and suppress it in OVX rats not treated with estrogen, suggesting a modulation by estrogen of the response to orexins. We examined the effects of orexin A on pulsatile LH secretion in OVX rats treated with a very small dose of estrogen so as to maintain the pulsatile secretion of LH. The estrogen treatment was done 24 h before the blood sampling by subcutaneously implanting a silicone tube (id = 1.5 mm, od = 2.5 mm, length = 25 mm) containing 17β-estradiol (E₂) dissolved in sesame oil at 20 µg/ml. In OVX rats treated with sesame oil as a control, the intracerebroventricular (icv) injection of orexin A (0.3 nmol, dissolved in 3 µl artificial cerebrospinal fluid) had no significant effect on the parameters of pulsatile LH secretion, i.e., pulse frequency and pulse amplitude, although it caused a small but statistically significant decrease in overall mean LH concentrations within 1 h. In OVX rats treated with E₂, the icv injection of orexin A significantly suppressed the pulsatile LH secretion; the frequency decreased for more than 2 h, inducing a rapid decline in overall mean LH concentrations. In view of the finding that a much higher dose of orexin A suppresses pulsatile LH secretion in OVX rats not treated with E₂, we suggest that the suppressive action of orexin A on pulsatile LH secretion is potentiated by estrogen.

The role of plasma renin activity in distinguishing patients with polycystic ovary syndrome (PCOS) from oligomenorrheic patients without PCOS

All the components of the renin-angiotensin system have been identified in the human ovary. Renin plays a major role in folliculogenesis, and possibly in follicular atresia. Polycystic ovary syndrome (PCOS)is characterized by early follicular atresia. We studied whether assessment of plasma renin activity would be useful for diagnosing PCOS and distinguishing PCOS and non-PCOS in oligomenorrheic patients.Patients were divided into three groups: PCOS group (group 1, n = 40), non-PCOS oligomenorrheic group (group 2, n = 30) and ovulatory control group (group 3, n = 30). Plasma renin activity was determinedin the early follicular phase of the menstrual cycle. Baseline serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, insulin, aldosterone and androgens (total testosterone,free testosterone, androstenedione, dehydroepiandrosterone sulfate and 17α hydroxyprogesterone) were determined in all groups. The mean LH level was lower (4.94 ± 4.65 mIU/ml) in control patientsthan in PCOS patients (12.9 ± 1.75 mIU/ml) and non-PCOS oligomenorrheic patients (10.8 ± 1.65 mIU/ml). There was no statistically significant difference between the groups regarding FSH levels.The mean plasma renin activity was 3.47 ± 0.29 ng/ml in the PCOS group. The mean plasma renin activity was 1.59 ± 0.21 ng/ml the non-PCOS oligomenorrheic group (statistically significiantdifferrence). There was no statistically significant difference between the non-PCOS oligomenorrheic (1.59 ± 0.21 ng/ml) and control groups (1.2 ± 0.16 ng/ml). Use of plasma renin activityalone as a diagnostic marker in PCOS is not useful, because the clinical findings of PCOS are heterogeneous and the pathogenesis is unclear. However, it can be used together with other variables to diagnosewomen with PCOS and to distinguish non-PCOS oligomenorrheic women from those with PCOS.

Restoration of LH output and 17β-oestradiol responsiveness in acutely ovariectomised holstein dairy cows pre-treated with a GnRH agonist (deslorelin) for 10 days

The objectives of the study were firstly to identify the role of the ovary in maintaining plasma luteinising hormone (LH) concentrations in cows treated with an implant of a potent GnRH agonist (deslorelin), and secondly to characterise the changes in LH following ovariectomy (OVX) in the same animals. Oestrus was synchronised in mature Holstein dairy cows and deslorelin implants were inserted 17 days later into two-third of the cows. A further 10 days later (day 0) all cows had bilateral OVX performed. A control group (CON; n=4) received no treatment and had blood samples collected at 15-min intervals for 8 h on the day prior to OVX (day −1) and similarly on days 4 and 10. One group (DES_IN; n=4) had implants in place for the duration of the study while another group had implants removed (DES_OUT; n=4) at the time of OVX. DES_IN cows were sampled hourly at each sampling session (days −1, +4 and +10), whereas DES_OUT cows were sampled similarly to CON except on day −1 when hourly samples were collected. Predictable post-operative increases in mean LH (0.61 ng/ml versus 1.79 ng/ml; P<0.01) and LH pulse amplitude (0.66 ng/ml versus 1.56 ng/ml; day −1 versus day +10; P<0.01) occurred after CON cows were ovariectomised. Smoothed LH means showed a delayed effect of time compared to arithmetic means. Pulse frequency was unchanged following OVX in CON cows. A comparison of all cows that had been treated with deslorelin from day −1 showed a significant elevation of smoothed mean LH compared to untreated cows (0.80 ng/ml versus 0.34 ng/ml; DES_IN and DES_OUT versus CON; P<0.05). DES_IN cows had a 54% reduction in mean LH from day −1 to +4 following OVX (1.05 ng/ml versus 0.48 ng/ml; P<0.01) indicating the probable involvement of the ovary in the maintenance of elevated basal LH. No further reduction was detected by day +10. The LH response to an intramuscular (IM) injection of 500 μg 17β-oestradiol (E2) on day +11 varied significantly between treatment groups ( P<0.01). CON cows showed a typical LH surge, reaching maximum concentrations (10.3 ng/ml) at 17.3 h post-injection. Even though low amplitude LH pulsatility had been restored in DES_OUT cows by day +4, there was an inconsistent response to E2 on day +12; one cow had an apparently normal surge yet, others showed only attenuated responses. Pulse amplitude in DES_OUT cows was lower at days +4 and +10 compared to CON ( P<0.05). DES_IN cows did not produce any surge after E2. Mean LH prior to OVX (day −1) remained unchanged following the 500 μg oestradiol injection (0.38 ng/ml versus 0.45 ng/ml pre-E2 versus post-E2 compared to 1.05 ng/ml pre-OVX). The results of this experiment implicated ovarian involvement in maintaining elevated basal LH output in cows that were chronically treated with a GnRH agonist. Individual cows varied in their LH surge response to exogenous E2 given 12 days after implant removal, even though LH pulse amplitude and frequency had been restored.

Disruption of the hypothalamic luteinizing hormone pulsing mechanism in aging men

The incremental nature of neuroendocrine aging suggests that subtle system dysregulation may precede overt axis failure. The present analyses unmask threefold disruption of pulsatile gonadotropin-releasing hormone (GnRH)-luteinizing hormone (LH) secretion in the aging male. First, by way of random effects-based deconvolution analysis, we document an elevated daily GnRH-LH pulse frequency in healthy older men [namely, mean (+/-SE) 23 +/- 1 (older) vs. 15 +/- 1 (young) LH secretory bursts/24 h, P < 0.001] and lower mean LH pulse mass [3.73 +/- 0.58 (older) vs. 5.46 +/- 0.66 (young) IU/l, P = 0.038]. However, total LH secretion rates and two-compartment LH elimination kinetics were comparable in the two age cohorts. Second, using the approximate entropy statistic, we show an equivalently random order-dependent succession of LH interpulse-interval lengths in young and older men, but a marked age-related deterioration of the ad seriatim regularity of LH pulse mass series in older individuals (P = 0.0057). Third, by modeling GnRH pulse-generator output as a Weibull renewal process (generalized Gamma density) to emulate loosely coupled GnRH neuronal oscillators, we identify an age-related reduction in the frequency-independent and order-independent variability of GnRH-LH interpulse-interval sets (P = 0.08). These findings indicate that the GnRH-LH pulsing mechanism in healthy older men maintains an increased mean frequency and lower amplitude of bursting activity, a reduced uniformity of serial LH pulse-mass values, and an impaired variability among interpulse-interval lengths. Thereby, the foregoing order-dependent and order-independent alterations in GnRH-LH signal generation in the aging human suggest a general framework for exploring subtle disruption of time-sensitive regulation of other neurointegrative systems.

Endogenous luteinizing hormone is not increased during a GnRH-a microdose flare protocol.

Objective: Microdose flare (MDF) stimulation protocols using GnRH agonist (GnRH-a) at 80 μg/d have been demonstrated to improve ART outcomes in poor responders. Higher dose GnRH-a (500μg/d) flare protocols have been associated with poor IVF outcomes in normal responders. It has been suggested that this was the result of elevated luteinizing hormone (LH) levels prior to hCG administration. LH levels have not been previously reported in normal responders using the MDF protocol. To determine whether LH levels were suppressed we examined LH levels in normal responders during a GnRH-a MDF protocol.Design: Cohort analysis of LH levels in patients undergoing ART using a GnRH-a MDF protocol in combination with follicle stimulation hormone (FSH) only.Materials/Methods: Patients aged 30–34, except those with chronic anovulation, undergoing an initial IVF cycle at our institution were started on a GnRH-a MDF protocol using FSH only. All patients starting in January 2001 were included. Patients were suppressed with oral contraceptives for at least 3 weeks prior to starting leuprolide acetate 40μg SQ BID on cycle day 3. FSH 150 IU q 12 hours was begun on cycle day 5. Both recombinant FSH and highly purified FSH were utilized. Blood samples collected for estradiol monitoring throughout stimulation were assayed for LH levels in batches. Intra-assay variation was 2%, inter-assay variation was 2.6%.Results: Mean patient age, days of stimulation, ampules of FSH, peak estradiol, and number of mature oocytes are shown in the table below. Forty percent of patients in this study group had a day 5 transfer. The mean LH value on the day of hCG administration was 2.3 mIU/mL. Data on LH level on the day of hCG was unavailable for one patient, however her level on the day prior to hCG administration was 2.0 mIU/mL. The pregnancy rate in this group exceeded 70%.Tabled 1Mean (range)Patient age (years)31.4 (30–33)Ampules used38.3 (32–44)Peak estradiol (pg/mL)5301.7 (1754–12618)Mature oocytes22.0 (2–40)LH on day of hCG (mIU/mL)2.3 (0.6–4.5) Open table in a new tab Conclusions: This study demonstrated that LH values are not elevated during a microdose flare protocol. Given the excellent pregnancy rates achieved, these data support the use of the microdose flare protocol in normal responders. Objective: Microdose flare (MDF) stimulation protocols using GnRH agonist (GnRH-a) at 80 μg/d have been demonstrated to improve ART outcomes in poor responders. Higher dose GnRH-a (500μg/d) flare protocols have been associated with poor IVF outcomes in normal responders. It has been suggested that this was the result of elevated luteinizing hormone (LH) levels prior to hCG administration. LH levels have not been previously reported in normal responders using the MDF protocol. To determine whether LH levels were suppressed we examined LH levels in normal responders during a GnRH-a MDF protocol. Design: Cohort analysis of LH levels in patients undergoing ART using a GnRH-a MDF protocol in combination with follicle stimulation hormone (FSH) only. Materials/Methods: Patients aged 30–34, except those with chronic anovulation, undergoing an initial IVF cycle at our institution were started on a GnRH-a MDF protocol using FSH only. All patients starting in January 2001 were included. Patients were suppressed with oral contraceptives for at least 3 weeks prior to starting leuprolide acetate 40μg SQ BID on cycle day 3. FSH 150 IU q 12 hours was begun on cycle day 5. Both recombinant FSH and highly purified FSH were utilized. Blood samples collected for estradiol monitoring throughout stimulation were assayed for LH levels in batches. Intra-assay variation was 2%, inter-assay variation was 2.6%. Results: Mean patient age, days of stimulation, ampules of FSH, peak estradiol, and number of mature oocytes are shown in the table below. Forty percent of patients in this study group had a day 5 transfer. The mean LH value on the day of hCG administration was 2.3 mIU/mL. Data on LH level on the day of hCG was unavailable for one patient, however her level on the day prior to hCG administration was 2.0 mIU/mL. The pregnancy rate in this group exceeded 70%. Tabled 1Mean (range)Patient age (years)31.4 (30–33)Ampules used38.3 (32–44)Peak estradiol (pg/mL)5301.7 (1754–12618)Mature oocytes22.0 (2–40)LH on day of hCG (mIU/mL)2.3 (0.6–4.5) Open table in a new tab Conclusions: This study demonstrated that LH values are not elevated during a microdose flare protocol. Given the excellent pregnancy rates achieved, these data support the use of the microdose flare protocol in normal responders.

NO RELATIONSHIP OF TESTICULAR SIZE AT ORCHIOPEXY WITH FERTILITY IN MEN WHO PREVIOUSLY HAD UNILATERAL CRYPTORCHIDISM

We determined whether testicular size at orchiopexy is predictive of fertility potential and whether size correlates with sperm parameters, hormone levels or testicular volume in adulthood. Testicular size obtained from the operative notes of patients who underwent unilateral orchiopexy was classified as normal, small or large for age. These data were compared with outcome data. Paternity data were included on 166 men who reported achieving or unsuccessfully attempting paternity for 12 or more months. Of the men 49 provided blood for hormone level measurement, 43 underwent semen analysis and in 29 testicular volume was determined. In the 166 men, including 98, 65 and 3 with small, normal and large testes for age at orchiopexy, respectively, there was no difference in paternity based on testicular size. Of those who achieved paternity time to conception did not differ based on size. Mean age at surgery also did not differ, nor did the percent of small versus normal testes in the age categories 0 to 2, 3 to 5, 6 to 8 and 9 to 11 years. There was no difference in men with small or normal testicular size at surgery in mean luteinizing hormone, follicle-stimulating hormone, testosterone or inhibin B. Sperm density, motility and morphology, and volume in adulthood of a previously undescended testis, previously descended testis or previously undescended and descended testes did not differ in these 2 groups, although the previously undescended testis was smaller than the contralateral testis. In men with a history of unilateral cryptorchidism small testicular size at orchiopexy is not associated with decreased paternity (89.8%), abnormal hormone levels, a lower sperm count or decreased testicular volume in adulthood.

Dose‐dependent effects of melengestrol acetate (MGA) on plasma levels of estradiol, progesterone and luteinizing hormone in cycling heifers and influences on oestrogen residues in edible tissues

Melengestrol acetat (MGA) is widely used as a growth promoting feed additive in cattle breeding in the USA and several other non‐European countries. To explore the physiological effects of MGA four heifers were fed during 8 weeks with 0.5 mg MGA daily as registered in the USA and two heifers each received 0, 1.5 or 5 mg/day, respectively. Plasma samples were collected twice a week and concentrations of MGA, progesterone (P4) and estradiol‐17β (E2‐17β) were quantified. The pulsatile secretion of luteinizing hormone (LH) was investigated in 6‐hour profiles before and during treatment. After slaughter the reproductive organs were examined and oestrogen residues in edible tissues were measured. Four days after the beginning of MGA feeding MGA concentrations in plasma reached levels of 30 and 100–400 pg/mL depending on the dose received. Three weeks after the beginning of MGA feeding P4 plasma concentrations had dropped to base levels below 0.3 ng/mL in all three treatment groups. Mean plasma E2‐17β levels increased in physiological range from 1 to 5 pg/mL during 0.5 mg MGA/day feeding with many acyclic peaks. Overdosed MGA decreased E2 levels and suppressed cyclic peaks. Number and size of ovarian follicles were not altered by any treatment. Mean LH levels and pulse frequencies increased significantly during labelled treatment (0.5 mg/day), while higher doses had reducing effects. The development of corpus luteum was suppressed. E2‐17β residues in fat increased about 300% following labelled MGA treatment.

Neural circuits regulating pulsatile luteinizing hormone release in the female guinea-pig: opioid, adrenergic and serotonergic interactions.

We studied three neurotransmitters involved in the regulation of pulsatile luteinizing hormone (LH) release: opioid peptides, serotonin and norepinephrine, using the ovariectomized guinea-pig. This is an attractive animal model due to the regularity of its LH pulses, enabling any disruptions to be clearly ascertained. In all experiments, a specific agonist or antagonist was administered, either alone or serially to enable detection of interactions, and effects on mean LH concentrations, pulse amplitude and interpulse interval were determined by PULSAR analysis. In the ovariectomized guinea-pig, catecholamines are stimulatory (acting through the alpha1 and alpha2 but not beta receptors, unlike other species), opioids inhibitory and serotonin permissively stimulatory to pulsatile LH release. Stimulatory effects of the opiate antagonist were not blocked by pretreatment with an alpha1- or alpha2-adrenergic antagonist. Similarly, pretreatment with the opiate antagonist did not prevent the suppression of LH release by alpha1 and alpha2 antagonists. This suggests that, in the guinea-pig, effects of opiates and catecholamines on LH release are exerted by independent pathways to luteinizing hormone releasing hormone (LHRH) neurones. For the opiate-serotonin interactions, pretreatment with the serotonergic antagonist did not block the stimulatory effect of the opiate antagonist on LH release. However, pretreatment with the opiate agonist could not be overcome by the serotonergic agonist. This suggests that the effects of the serotonin system on LHRH release may be indirectly mediated by opioid neurones. Taken together, these studies demonstrate that the three neurotransmitter systems studied are critically involved in normal pulsatile LH release in the female guinea-pig, and demonstrate novel functional relationships between the opioid and the adrenergic and serotonergic systems.

The Effects of a Single Long Photoperiod on Induction and Dissipation of Reproductive Photorefractoriness in European Starlings

In many birds, long photoperiods stimulate gonadal maturation but also cause photorefractoriness, leading to gonadal regression. While much is known about the neuroendocrinology of photostimulation, little is known about photorefractoriness, partly due to lack of an experimental model. This study aimed to develop a model to test whether a single long photoperiod (LP) initiates the mechanism leading to photorefractoriness. It made use of the fact that in castrated European starlings, luteinizing hormone (LH) is low in photorefractory birds and high in photosensitive birds. In the first experiment, groups of castrated photorefractory birds were transferred from a long to a short photoperiod and then exposed to one LP every 5, 10, 20, 30, 40, or 60 days. In birds exposed to one LP every 5 days, LH stayed low. In birds exposed to one LP every 10 days, each LP caused a pulse in LH, but mean LH remained low. One LP every 20 days increased LH 6 days later, followed by a decrease at 11 days and then a further increase, so that overall, LH increased slowly. In birds exposed to one LP every 30, 40, or 60 days, LH increased at the same rate as in short photoperiod controls. Each LP did not cause a significant increase in LH, but did cause a decrease. A second experiment examined the changes in LH following a LP in more detail. Castrated starlings had been exposed to one LP every 14 days for 16 weeks. On the day of the final LP, LH values were midway between photorefractory and photosensitive values. The LP caused an increase in LH from the second day to a peak after 7 days. Thereafter, LH declined to initial values after 14 days, followed, in the absence of further LP, by a second increase to photosensitive values. These results suggest that the mechanisms causing photostimulation and photorefractoriness are both initiated during the first long photoperiod. That gonadal maturation precedes regression must reflect the relative rates at which the two processes reach completion.

Effects of Systemic Blockade of Nitric Oxide Synthases on Pulsatile LH, Prolactin, and GH Secretion in Adult Male Rats

Background: Nitric oxide (NO) has emerged as an important neurotransmitter involved in the control of the neuroendocrine function. NO acts at hypothalamic, pituitary, and gonadal levels. Previous data from our laboratory showed that blockade of NO generation, after systemic administration of a NO synthase inhibitor (Nω-nitro-arginine methyl ester, NAME), increased the luteinizing hormone (LH) secretion in intact and ovariectomized females, whereas a blockade of spontaneous and steroid-induced LH and prolactin surges after NO synthase inhibition has been also described. Methods and Results: Adult male rats were implanted with chronic intra-auricular cannulae and 5 days later sampled at 15-min intervals during 6 h (10.00–16.00 h). Administration of NAME (40 mg/kg at 08.00 and 13.00 h) stimulated significantly (p ≤ 0.01) the LH secretion, increasing LH pulse amplitude (0.58 ± 0.14 vs. 0.08 ± 0.01 ng/ml in controls), mean LH levels (0.64 ± 0.15 vs. 0.15 ± 0.03 ng/ml in controls), and area under curve (239 ± 56 vs. 57 ± 13 in controls). This effect was blocked by coadministration of sodium nitroprusside (SNP), a NO donor (0.5 mg/kg). The action of NAME was observed 3 h after administration, in contrast to the earlier response detected in female rats, and it appeared selective for LH, as prolactin and growth hormone secretion remained unchanged. Further analysis was carried out to determine whether the effect of NAME on the LH secretion was indirect and mediated by changes in testosterone release. To this end, adult male rats were decapitated 2 h after administration of NAME (40 mg/kg), SNP (0.5 mg/kg), or L-nitro-arginine methyl ester (L-AME), a substrate for NOS (1 g/kg). The serum testosterone concentrations were unchanged after NAME administration, but inhibited by SNP and L-AME. Finally, the effect of NAME and SNP on in vitro testosterone secretion was analyzed. NAME (10 mM) did not affect basal testosterone production, but inhibited the human chorionic gonadotropin stimulated testosterone secretion. Conclusions: These data strongly suggest that the stimulatory effect of NAME on LH secretion is not due to an inhibition of testosterone release and is exerted at the hypothalamic-pituitary level.

Association of Hypogonadism and Estradiol Levels with Bone Mineral Density in Elderly Men from the Framingham Study

Both hypogonadism and low estrogen levels adversely affect bone health in young men. In elderly men, who are at greatest risk for osteoporotic fracture, the influence of hypogonadism on bone mineral density remains unclear, as does the relative effect of estrogen status compared to hypogonadism. To examine the relation of hypogonadism and estrogen status to bone mineral density in elderly men. Community-based, prospective cohort study. Framingham, Massachusetts. Male participants of the Framingham Study. Total testosterone, total estradiol, and luteinizing hormone were measured in participants at all four biennial examinations from 1981 to 1989. Values from at least three of four examinations were averaged. Hypogonadism was defined as a mean testosterone level less than 10.4 nmol/L (<3.0 ng/mL) or a mean luteinizing hormone level of 20 IU/L or greater. An alternate definition of hypogonadism based only on a mean testosterone level less than 10.4 nmol/L (<3.0 ng/mL) was also used. In 1988-1989, bone mineral density was measured at the proximal femur (femoral neck, Ward triangle, and trochanter) and lumbar spine by using dual-photon absorptiometry and at the radial shaft by using single-photon absorptiometry. The association of hypogonadism with bone mineral density was examined with adjustment for confounders, including estradiol levels. A similar model that adjusted for hypogonadism was used to examine the association of estradiol level (ranked as quartiles) with bone mineral density. Of 448 men with bone mineral density measurements, 405 had evaluable hormone levels (mean age, 75.7 years [range, 68 to 96 years]); 71 (17.5%) of the 405 men were hypogonadal. Bone mineral density at any site did not significantly differ in hypogonadal men compared with eugonadal men (for example, bone mineral density at the femoral neck was 0.89 g/cm(2) vs. 0.87 g/cm(2), respectively; P > 0.2), even when alternate definitions of hypogonadism were used. In contrast, compared with the lowest estradiol quartile, men with higher estradiol levels had greater mean bone mineral density at all sites (for example, bone mineral density at the femoral neck was 0.84 g/cm(2), 0.88 g/cm(2), 0.86 g/cm(2), and 0.91 g/cm(2) from the lowest to the highest estradiol quartile; P for trend = 0.002). The difference in mean bone mineral density between men in the lowest and those in the highest estradiol quartile levels was similar to the effect of 10 years of aging on bone mineral density. In elderly men, hypogonadism related to aging has little influence on bone mineral density, but serum estradiol levels have a strong and positive association with bone mineral density.

Attenuation of Luteinizing Hormone Surges in Neuropeptide Y Knockout Mice

To clarify the role of neuropeptide Y (NPY) in the regulation of the reproductive axis, these experiments evaluated the extent to which reproductive hormone secretions may be compromised in the absence of NPY expression. In NPY knockout (NPY-KO) and wild-type (WT) mice, hormone secretions were analyzed under conditions of basal release, following ovariectomy (OVX), in proestrus, after estrogen treatments which induce gonadotropin surges and after injection of gonadotropin-releasing hormone (GnRH). Radioimmunoassays of serum from metestrous females revealed that basal luteinizing hormone (LH), follicular-stimulating hormone (FSH), estrogen and progesterone levels, as well as hypothalamic GnRH tissue concentrations, were not different between the two genotypes. The LH and FSH levels and GnRH tissue concentrations were likewise similar in WT and NPY-KO mice 5 and 10 days following OVX. Significant differences in LH levels were observed however when animals were exposed to pheromone stimulation (male mouse urine) to induce preovulatory LH surges. In proestrous animals, mean LH levels at 18.30–19.00 h were reduced by about 66% in NPY-KO versus WT mice (4.33 ± 1.12 ng/ml in the WT mice vs. 1.47 ± 0.42 ng/ml in the NPY-KO mice, p = 0.028). Despite diminishment of LH surges in NPY-KO mice, corpora lutea were equally abundant in the ovaries of NPY-KO and WT mice. In an additional experiment, a surge-inducing regimen of estradiol-17-β (E₂) and estradiol benzoate (E₂B) was administered to OVX animals. The LH surges in the NPY-KO animals treated in this manner were again diminished by approximately 50% compared to corresponding values in WT animals (WT mice 7.33 ± 0.97 ng/ml, NPY-KO mice 3.58 ± 0.74 ng/ml; p = 0.0063). To assess the contribution of altered pituitary responsiveness to the diminishment of LH surges, LH responses to a GnRH challenge (200 ng/kg subcutaneously) were determined; NPY-KO animals exhibited LH responses that were significantly reduced compared to values in WT mice (WT mice 4.88 ± 0.56 ng/ml, NPY-KO mice 3.00 ± 0.41 ng/ml; p = 0.013). Taken together, these observations do not support the idea that NPY plays a major role in the regulation of basal gonadotropin secretion or in mediating negative feedback actions of gonadal hormones. They demonstrate however that preovulatory NPY release is required for normal amplification of the LH surge that occurs on proestrus. Involvement of NPY in the generation of normal LH surges is partially mediated by the ability of the peptide to prime the anterior pituitary gland to GnRH stimulation.