Basal Luteinizing Hormone Concentrations Research Articles

Elevated Pre-injection Basal Luteinizing Hormone Concentrations are Common in Girls Treated for Central Precocious Puberty

Objective:A consensus on how to monitor girls with central precocious puberty (CPP) during gonadotropin-releasing hormone agonist (GnRHa) treatment is lacking. Increased, unstimulated basal luteinizing hormone (LH) concentrations have been suggested to indicate lack of suppression. The aim was to evaluate pre-injection basal LH concentrations during GnRHa (leuprorelin 3.75 mg) treatment every four weeks in girls with CPP.Methods:Medical records were reviewed for girls with CPP treated at a single center from 2014-2019. Clinical characteristics and laboratory findings during treatment were systematically recorded.Results:A total of 587 GnRHa pre-injection basal LH concentrations were analyzed in 74 girls. Basal LH was pubertal (≥0.3 IU/L) in 53.5% of blood samples and 87.8% of all girls had a pubertal basal LH concentration at least once. A GnRH test (n=29) was repeated in 23 girls due to suspicion of clinical progression, elevated basal LH or recordable estradiol concentrations. None had a stimulated LH >3.1 IU/L. The predictability of treatment suppression (specificity) of basal LH concentrations was 12.0% when compared to repeated GnRH stimulation tests. Despite shortening the GnRHa injection interval to three weeks, basal LH concentrations remained pubertal in 85.7% girls. A significant reduction in height standard deviation score (p<0.001) and bone age advance (p<0.001) was observed during treatment.Conclusion:Pre-injection basal LH remains at pubertal concentrations during treatment with leuprorelin 3.75 mg in girls with CPP. Clinical monitoring of pubertal progression is preferable to routine basal LH concentrations. Repeat GnRH stimulation testing should be regarded as the gold standard.

The effects of delta-9-tetrahydrocannabinol exposure on female menstrual cyclicity and reproductive health in rhesus macaques

To determine the dose-dependent effect of contemporary marijuana exposure on female menstrual cyclicity and reproductive endocrine physiology in a nonhuman primate model. Research animal study. Research institute environment. Adult female rhesus macaques (6-12 years of age; n = 8). Daily delta-9-tetrahydrocannabinol (THC) edible at medically and recreationally relevant contemporary doses. Menstrual cycle length (MCL), anti-Müllerian hormone, prolactin, basal follicle-stimulating hormone (FSH), estradiol (E2) and progesterone, luteinizing hormone (LH), and thyroid-stimulating hormone. The average before THC weight was 6.9 kg (standard deviation, 0.8), and at the highest THC dosing, the average weight was 7.2 kg (standard deviation, 0.8). With increasing THC dosing, MCL and FSH concentrations increased, while basal E2 concentration was stable. The average MCL concentration increased 4.0 days for each mg/7 kg/day of THC (95% CI, 1.4-6.6 days). Follicle-stimulating hormone concentration increased significantly with increasing THC dose, 0.34 ng/mL for each mg/7 kg/day of THC (95% CI, 0.14-0.57 ng/mL). No significant trends were observed between THC dosing and average basal progesterone, anti-Müllerian hormone, prolactin, LH, or thyroid-stimulating hormone concentrations. In rhesus macaques, a dose response toward increased MCL and basal FSH concentrations but plateau of basal E2 and LH concentrations was observed with increasing THC dosing, suggesting ovulatory dysfunction. Further studies are needed to determine the effects of a longer duration of exposure and whether the significant increase in MCL and FSH concentrations results in reduced fecundity.

Time Points for Gonadotropin-Releasing Hormone Stimulation Test Results in Korean Children.

The gold standard for the laboratory diagnosis of central precocious puberty is based on the measurement of luteinizing hormone (LH) after gonadotropin-releasing hormone (GnRH) stimulation. We sought to investigate the laboratory data for GnRH stimulation testing using samples collected from Korean children at different time points. Sampling times were at the basal time point (0) and 15, 30, 45, 60, 90, and 120 min after GnRH stimulation. Pubertal response was defined as occurring when the peak LH concentration was 5 IU/L or more and rose to at least 2 times the basal LH concentration after GnRH stimulation. During the study period, 19,990 test results from 1958 Korean children (1841 females aged 1.3–8.9 years and 117 males aged 7.3–9.9 years) were obtained. Among the 1958 children, 1232 (62.9%) showed pubertal responses. The receiver operating characteristic curve that demonstrated the greatest area under the curve (AUC) among all examined time points was 45 min after GnRH stimulation in males (AUC 0.982, 95% CI 0.938–0.998) and 60 min in females (AUC 0.975, 95% CI 0.967–0.981). The combination of 45 min and 60 min showed the greatest AUC (0.996, 95% confidence interval 0.991–0.998), with a sensitivity level of 99.1% and a specificity of 100% for all children. The results of this study provide a possibility for a reduction in sampling time points (45 min and 60 min) to identify the presence of a pubertal response after GnRH stimulation in Korean children.

Hormonal Changes in High-Level Aerobic Male Athletes during a Sports Season.

The aim of this study was to determine the possible changes in plasma of several hormones such as Luteinizing Hormone, Testosterone, Cortisol and Insulin in endurance runners during the sports season. Twenty-one high-level male endurance runners (22 ± 3.2 years, 1.77 ± 0.05 m) participated in the study. Basal plasma hormones were measured at four moments during the season (initial, 3, 6 and 9 months), and were analyzed using ELISA (enzyme-linked immunosorbent assay). Testosterone and Luteinizing Hormone (LH) suffered very significant decreases (p < 0.01) at 3 months compared with the beginning and an increase (p < 0.05) at 6 and 9 months compared with 3 months. Insulin level was significantly lower (p < 0.05) at 3, 6 and 9 months compared with the initial test. Insulin and cortisol were associated inversely (r = 0.363; β = −0.577; p = 0.017) and positively (r = 0.202; β = 0.310; p = 0.043), respectively, with the amount of km per week performed by the runners. There was a significant association between km covered at a higher intensity than the anaerobic threshold and I (r = 0.580; β = −0.442; p = 0.000). Our findings indicate that testosterone, LH and insulin were more sensitive to changes in training volume and intensity than cortisol in high-level endurance runners. Basal testosterone and LH concentrations decrease in athletes who perform a high volume of aerobic km in situations of low energy availability.

Temporal changes in serum luteinizing hormone following ovariohysterectomy and gonadotropin-releasing hormone vaccination in domestic cats.

Measurement of circulating luteinizing hormone (LH) concentrations in cats and temporal changes following ovariohysterectomy (OHE) or possibly GnRH vaccination may be informative for assessing their fertility, contraception or sterilization status. In this study, serum LH concentrations were measured in domestic cats (n=6) immediately prior to and up to 120days post-OHE. Basal LH concentrations of females previously subjected to OHE (n=4; ~1.5years post-OHE) were compared pre- and post-vaccination with a GnRH immunocontraceptive, and to LH concentrations in intact females. Basal serum LH concentrations (2.67±0.43ng/ml; mean±SEM) in intact females increased (p<.01) by 30days post-OHE (5.65±0.87ng/ml) but then declined (p<.05) to pre-OHE levels (mean range, 3.26-3.62ng/ml) at days 60-120 post-OHE. Serum LH (3.84±0.51ng/ml) in four females ~1.5years after OHE tended to be higher (p=.10) than those of intact females prior to OHE. Three months following first or second GnRH immunocontraceptive vaccine treatment, serum LH values in females previously subjected to OHE decreased (p<.05) to concentrations similar to those observed in intact females. Our preliminary results suggest that OHE of domestic cats causes a marked increase in basal LH levels within the first few weeks after ovariohysterectomy followed by a return to pre-OHE basal values over the next several months. Reduced LH concentrations after GnRH vaccine may indicate the effectiveness of the immunocontraceptive in reducing the circulating levels of GnRH, thereby reducing secretion of LH.

Acquired Hypogonadotropic Hypogonadism (AHH) in Thalassaemia Major Patients: An Underdiagnosed Condition?

IntroductionIn males, acquired hypogonadotropic hypogonadism (AHH) includes all disorders that damage or alter the function of gonadotropin-releasing hormone (GnRH) neurons and/or pituitary gonadotroph cells. The clinical characteristics of AHH are androgen deficiency and lack, delay or halt of pubertal sexual maturation. AHH lead to decreased libido, impaired erectile function, and strength, a worsened sense of well-being and degraded quality of life (QOL).Patients and methodsWe studied 11 adult men with thalassemia major (TM) aged between 26 to 54 years (mean ± SD: 34.3 ± 8.8 years) with AHH. Twelve age- and sex-matched TM patients with normal pubertal development were used as a control group. All patients were on regular transfusions and iron chelation therapy. Fasting venous blood samples were collected two weeks after transfusion to measure serum concentrations of IGF-1, free thyroxine (FT4), thyrotropin (TSH), cortisol, luteinizing hormone (LH), follicle stimulating hormone (FSH), total testosterone (TT), prolactin and estradiol (E2), glucose, urea, creatinine and electrolytes (including calcium and phosphate). Liver functions and screening for hepatitis C virus seropositivity (HCVab and HCV-RNA) were performed. Iron status was assessed by measuring serum ferritin levels, and evaluation of iron concentrations in the liver (LIC) and heart using MRI- T2*. Bone mineral density was measured at the lumbar spine (L1–L4) for all patients with AHH by dual energy X-ray absorptiometry (DXA) using Hologic QDR 4000 machine.ResultsThe mean basal serum LH and FSH concentrations in AHH patients were 2.4 ± 2.2 IU/L and 1.2 ± 0.9 IU/L respectively; these, values were significantly lower compared to the control group. Semen analysis in 5 patients with AHH showed azoospermia in 3 and oligoasthenozoospermia in 2. The percentage of patients with serum ferritin level >2000 ng/ml (severe iron load) was significantly higher in AHH patients compared to controls, 5/11 (45.4 %) versus1/12 (8.3%), p=0.043. Heart iron concentrations (T2* values) were significantly lower in AHH patients compared to controls (p=0.004). Magnetic resonance imaging in the 3 azoospermic patients revealed volume loss and reduction of pituitary signal intensity. Heart T2* values were significantly reduced in the AHH group vs. the controls (p=0.004). On the other hand, liver iron concentration (mg/g dry weight) was not different between the two groups of TM patients. Using DXA, 63.6 % (7/11) of patients with AHH were osteoporotic, and 36.3 % (4/11) were osteopenic.ConclusionsIn this cohort of thalassemic patients iron overload and chronic liver disease appear to play a role in the development of AHH. Treatment of AHH in TM patients is a vital and dynamic field for improving their health and QOL. Early identification and management of AHH are very crucial to avoid long-term morbidity, including sexual dysfunction and infertility. Therapy aims to restore serum testosterone levels to the mid–normal range. Many exciting opportunities remain for further research and therapeutic development.

Acute Effects of Blood Transfusion on Spermatogenesis and Pituitary Gonadal axis in Eugonadal Males with Beta Thalassemia Major (pilot study)

AbstractAbstract 1027 Objective:To evaluate semen parameters and measure serum follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T) and insulin-like growth factor-I (IGF-I) concentrations before and 7 days after packed red cell transfusion (PCTx) in young adults with thalassemia major (TM). Design:Prospective study. Setting, Patients, Interventions:We studied the effect of blood transfusion on semen parameters, the endocrine functions in 10 young adults with TM, aged from 17 to 32 years, with full pubertal development (Tanner’s stage 5) (euogonadal),and capacity to ejaculate. They were regularly transfused since early childhood and underwent chelation therapy using desferrioxamine which was replaced by deferasirox for the last 4 –5 years. At the time of the study their serum ferritin levels ranged from 500 to 5922 ng/ml (mean2686 ng/ml). Basal serum concentrations of FSH, LH, T and IGF-I were evaluated before and 7 days after packed red cell transfusion (PCTx). Main Outcome Measures and Results:After PCTx significant increase of Hb from 8.7 +/− 0.86 g/dl to 11.1 +/− 0.82 g/dl was associated with increased testosterone (from 16.5 +/− 8 nmol/L to 20 +/− 8.8 nmol/L, IGF-I (from 173 +/− 46ng/ml to 214 +/− 61ng/ml) and gonadotropins’ concentrations. Total sperm count increased significantly from 57.8 +/− 38.3 million/ml to 166 +/− 132 million/ml and rapid progressive sperm motility progressive motility increased from 20.6+/− 16.6 % to 79.7 +/− 67.4 %. After PCTx, LH concentrations were correlated significantly with T concentrations (r = 0.434, p < 0.001) and sperm volume and count (r = 0.439 and r = 0.376 respectively, p: 0.01). The increase of IGF-I concentration was correlated significantly with Hb level after PCTx (r = 0.535, p < 0.001) and negatively with ferritin concentration (r = −0.458, p < 0.001). Significant correlation were found between serum T concentrations and semen parameters before and after PCTx including sperm count (r = 0.658 and r = 0.73 respectively, p < 0.001)rapid progressive motility (r = 0.675 and r = 0.758 respectively p < 0.001), and the number of sperms with normal morphology (r = 0.752 and r = 0.834 respectively, p < 0.001) IGF-I levels and seminal parameters. No correlations were found between serum FSH and IGF-I concentrations and seminal parameters. Conclusion:Our study suggests that in thalassemic males blood transfusion is associated with significant acute enhancement of sperm parameters and with an increased concentrations of serum testosterone, LH, FSH and IGF-I. These “acute” effects on spermiogenesis are reached with an unknown mechanism/s and suggest a number of pathways that need further human and/or experimental studies.Table 1Hormonal and sperm data before versus after blood transfusion in thalassemic malesBeforeAfterP valuen = 10n = 10Hb (g/dl)8.7 +/− 0.8611.1 +/− 0.82 *0.000046LH (IU/L)2.5 +/− 1.653.8 +/− 1.87*0.049FSH (IU/L)3.3 +/− 2.454.4 +/− 2.27*0.008Testosterone (umol/L)16.5 +/− 820 +/− 8.8*0.0018Basal GH (ng/ml)0.88 +/− 1.3NDPeak GH (ng/ml) after clonidine6.7 +/− 2.66NDIGF-I (ug/L)173 +/− 46214 +/− 61*0.003Seminal parametersVolume (ml)1.65 +/− 0.782.1 +/− 0.58*0.0406Total sperm count (mil/ml)57.8 +/− 38.3166 +/− 132*0.0059Rapid progressive motility (%)23.9 +/− 15.364.9 +/− 12.6*0.0026Normal forms (%)41.7 +/− 17.648.3 +/− 12.4*0.045ND= not done.Table 2Correlations (R values) between serum testosterone level and sperm parameters before (1) and after (2) blood transfusionTestosterone (1)Testosterone (2)Sperm count (million/ml)10.660.73Volume (ml)10.430.47total PM (%) 10.680.76RPM (%) 10.690.71Normal morphology (%) 10.750.73Sperm count (million/ml)20.680.75Volume (ml)20.460.51Total PM 20.660.74RPM (%) 20.680.73Normal morphology (%) 20.750.83Abbreviations: TPM = Total progressive motility (%); RPM= Rapid Progressive motility (%); 1= before blood transfusion; 2 = after blood transfusion. Disclosures:Yassin:Hamad medical corporation MRC: Employment, Research Funding. Soliman:Hamad medical corporation MRC: Employment, Research Funding. Elawa:Hamad medical corporation MRC: Employment, Research Funding.

Acute Effects of Blood Transfusion On Pituitary Gonadal Axis and Sperm Parameters in Young Males with Sickle Cell Disease (SCD) Pilot Study

AbstractAbstract ▪3209▪This icon denotes a clinically relevant abstract Objective:To evaluate semen parameters and measure serum follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) concentrations before and 7 days after packed red cell transfusion (PCTx) in young adults with sickle cell disease (SCD). Design:Prospective study. Setting, Patients:This study investigated 18 young adults with transfusion – dependent SCD, aged 20.7 +/− 2.88 years, with full pubertal development (Tanner’s stage 5) (euogonadal), and capacity to ejaculate. They were regularly transfused since early childhood and underwent chelation therapy using desferrioxamine which was replaced by deferasirox for the last 4–5 years. Ten were on top-up transfusion (TTx) and 8 were on exchange transfusion (ETx) regimen. At the time of the study their serum ferritin levels were 1488 +/− 557ng/ml. Basal serum concentrations of FSH, LH, T and IGF-I were evaluated before and 7 days after packed red cell transfusion (PCTx). Interventions:We studied the effect of PCTx on semen parameters and the endocrine functions in these 18 patients with SCD. Main Outcome Measures and Results:After Packed RBCs Transfusion(PCTx) significant increase of Hb from 8.5 +/− 1.17 g/dl to 10.5 +/− 0.4 g/dl was associated with increased testosterone (12.3 +/− 1.24 nmol/L to 14.23 +/− 1.22nmol/L and gonadotropins’ concentrations.Total sperm count increased significantly from 87.4 +/− 24.6 million/ml to 146.2 +/− 51.25 million/ml and total progressive sperm motility (TPM) from 40.8 +/− 11.1 million/ml to 93.4 +/− 38.3 million/ml, and rapid progressive sperm motility progressive motility (RPM) increased from 29.26 +/− 8.75 million/ml to 67.4 +/− 29 million/ml. After PCTx the total sperm count, TPM and RPM were significantly higher in the ETx group versus the TTx group.Before and after PCTx, Testosterone (T) concentrations were correlated significantly with sperm total count, volume, TPM and RPM (r = 0.53, 0.55, 0.42 and 0.38 respectively, p: 0.01). Before and after PCTx, hemoglobin (Hb) concentrations were correlated significantly with Sperm count, TPM, RPM and % of sperms with normal morphology (r= 0.60, 0.69, 0.66 and 0.86 respectively, p < 0.001). Conclusion:Our study suggests that in males with SCD blood transfusion is associated with significant acute enhancement of sperm parameters and with an increased concentration of serum testosterone, LH and FSH. Improvements of sperm parameters were significantly higher in the Exchange Transfusion group vs. the Top up Transfusion group. These “acute” effects on spermatogenesis are reached with an unknown mechanism/s and suggest a number of pathways that need further human and/or experimental studies.TableHormonal and sperm parameters in patients with SCD before and after transfusionSCD-ExchangeSCD-Top-upTSCD-Totaln = 8n = 10n = 18Age (y)20.33 +/− 2.1621 +/− 3.6720.7 +/− 2.88LH-13.83 +/− 0.754.8 +/− 0.974.4 +/− 0.94LH-25.5 +/− 0.555.9 +/− 1.175.7 +/− 0.85FSH-15.5 +/− 1.055.8 +/− 0.975.4 +/− 1.46FSH-26.67 +/− 1.757.11 +/− 0.936.6 +/− 1.8Testost-112.1 +/− 1.4512.48 +/− 1.4212.3 +/− 1.24Testost-214.2 +/− 1.1714.26 +/− 1.3214.23 +/− 1.22Hb-17.9 +/− 1.58.1 +/− 1.98.5 +/− 1.17Hb-210 +/− 1.210.9 +/− 0.210.5 +/− 0.4Ferritin2085 +/− 3751189 +/− 2251488 +/− 557Sperm Count-185.3 +/− 15.590.56 +/− 2284.4 +/− 24.6Sperm Count-2197 +/− 38.4122.7 +/− 23.5146.2 +/− 51.25Volume-1(ml)2.5 +/− 0.322.11 +/− 0.552.1 +/− 0.63Volume-2 (ml)2.83 +/− 0.42.22 +/− 0.52.35 +/− 0.7Total PM (M/ml)-144.7 +/− 7.341.8 +/− 7.740.8 +/− 11.1Total PM (M/ml)-2129.2 +/− 3775.3 +/− 19.1693.4 +/− 38.3RPM (M/ml)-132 +/− 10.127.44 +/− 7.729.26 +/− 8.75RPM (M/ml)-288.2 +/− 3153.56 +/− 18.567.4 +/− 29.1NPM(M/ml)-117.8 +/− 9.1525.3 +/− 10.821.6 +/− 10.25NPM(M/ml)-227.8 +/− 12.222.7 +/− 9.1528.5 +/− 12.7Immotile-122.8 +/− 6.723.44 +/− 9.223.2 +/− 8Immotile-240 +/− 15.924.67 +/− 7.2630.8 +/− 13.45Normal morphology-132.7 +/− 5.4331.44 +/− 5.4331.9 +/− 5.27Normal morphology-257.2 +/− 3.351.56 +/− 1.1353.8 +/− 3.57*p < 0.05 Exchange transfusion group (ETx) versus Top-up group (PCTx).#p < 0.05, after versus before PCTx.1 = before, 2 = after PCTx. Disclosures:Yassin:Hamad medical corporation MRC: Employment, Research Funding. Soliman:Hamad medical corporation MRC: Employment, Research Funding. Elawwa:Hamad medical corporation MRC: Consultancy, Research Funding.

Disorders of sexual development and associated changes in the pituitary-gonadal axis in dogs

Normal sexual differentiation depends on completion of chromosomal sex determination, gonadal differentiation, and development of the phenotypic sex. An irregularity in any of these three steps can lead to a disorder in sexual development (DSD). We examined nine dogs with DSD by abdominal ultrasonography, laparotomy, histologic examination of the gonads, and reproductive tract, cytogenetic analysis, and mRNA expression of the SRY gene. We also determined the plasma concentrations of luteinizing hormone (LH), estradiol-17β, and testosterone before and after administration of gonadotropin-releasing hormone (GnRH) and compared these results with those obtained in anestrous bitches and male control dogs. The gonads of three dogs with DSD contained both testicular and ovarian tissue, while in the other six only testicular tissue was found. Each of the dogs had a uterus. Based on gynecologic examination, cytogenetic analysis, and the histology of the gonads, seven of the nine dogs appeared to be XX sex reversals. Three of these were XX true hermaphrodites and four were XX males; the other two dogs had incomplete XY gonadal dysgenesis. All seven XX sex-reversed dogs were found to be negative for the SRY gene by polymerase chain reaction. The basal plasma luteinizing hormone (LH) concentration was significantly higher in dogs with DSD than in anestrous bitches but not significantly different from that in male dogs. The basal plasma LH concentration increased significantly after GnRH administration in all dogs with DSD. The basal plasma estradiol concentration was significantly higher in dogs with DSD than in anestrous bitches but not significantly different from that in male dogs. The basal plasma testosterone concentration was lower in dogs with DSD than in male dogs. In all dogs with DSD both the basal and GnRH-induced plasma testosterone concentrations were above the upper limit of their respective ranges in the anestrous bitches. In conclusion, the secretion of LH and estradiol in these dogs with DSD, all of which had testicular tissue in their gonads, was similar to that in male control dogs. These results indicate that the basal and/or GnRH-stimulated plasma testosterone concentration might be used to detect the presence of testicular tissue in dogs with DSD.

Effects of gonadotropin-releasing hormone administration on the pituitary-gonadal axis in male and female dogs before and after gonadectomy

GnRH-stimulation tests were performed in 14 female and 14 male client-owned dogs of several breeds, before and 4 to 5 mo after gonadectomy. The aim of the study was to obtain more insight into the pituitary-gonadal axis in intact and neutered dogs and to establish reference values. Basal plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations were increased significantly after gonadectomy in both bitches and male dogs. In both males and females ranges of the basal plasma FSH concentrations, before and after gonadectomy, did not overlap as opposed to the overlap in ranges of the basal plasma LH concentrations. Before gonadectomy basal plasma LH concentrations were lower and basal plasma FSH concentrations were higher in bitches than in male dogs. After gonadectomy these basal values did not differ significantly. GnRH administration before gonadectomy resulted in an increase in plasma LH and FSH concentrations in both genders. GnRH administration after gonadectomy produced an increase only in plasma LH concentrations in both genders, and a just significant increase in plasma FSH in castrated male dogs. GnRH administration before gonadectomy resulted in a significant increase in plasma testosterone concentration in both genders. In males ranges of basal and GnRH-stimulated plasma testosterone concentrations before and after gonadectomy did not overlap. Basal plasma estradiol concentrations were significantly higher in intact males than in castrated males and their ranges did not overlap. The basal estradiol concentrations in bitches before and after ovariectomy were not significantly different. At 120 min after GnRH administration, ranges of plasma estradiol concentration of intact and ovariectomized bitches no longer overlapped. In conclusion, basal plasma FSH concentration appears to be more reliable than basal plasma LH concentration for verification of neuter status in both male and female dogs. The basal plasma testosterone concentration appears to be reliable for verification of neuter status in male dogs. The plasma estradiol concentration at 120 min after GnRH administration can be used to discriminate between bitches with and without functional ovarian tissue.

Luteinizing hormone secretion as influenced by age and estradiol in the prepubertal gilt

The aim of this study was to determine if there is an age related reduction in the sensitivity of the negative feedback action of 17β-estradiol (estradiol) on luteinizing hormone (LH) secretion in the prepubertal gilt. Ovariectomized gilts at 90 ( n = 12), 150 ( n = 11) or 210 ( n = 12) days of age received estradiol benzoate (EB) osmotic pump implants 6/group and the remaining animals received vehicle control (C) implants except for 150-day C ( n = 5) on Day 0. On Day 10 blood samples were collected every 15 min for 8 h and serum LH and estradiol concentrations were measured. Serum estradiol concentrations averaged 5 ± 1, 5 ± 1 and 7 ± 2 pg/ml for the 90-, 150- and 210-day-old gilts implanted with estradiol, respectively, whereas, serum estradiol concentrations was undetectable in C gilts. Mean serum LH concentrations, basal LH concentrations and serum LH pulse amplitude were less in EB-treated gilts at all ages compared to control animals. In contrast, LH pulse frequency initially was less in EB-treated gilts but subsequently increased ( P < 0.04) with age (from 0.8 ± 0.2 at 90 days to 5.2 ± 0.2/8 h at 210 days), and at 210 days of age the pulse frequency was similar to C gilts. These results demonstrate an age related reduction in the sensitivity to the negative feedback action of estradiol on LH secretion and support the idea that the gilt conforms to the gonadostat hypothesis.

Alterations of the pituitary-ovarian axis in dogs with a functional granulosa cell tumor

Information on the pituitary-ovarian axis in dogs with a granulosa cell tumor (GCT) is lacking. Therefore, we investigated the plasma concentrations of luteinizing hormone (LH) and estradiol before and after gonadotropin-releasing hormone (GnRH) administration in seven bitches with a functional GCT (GCT-total), of which three were intact (GCT-intact) and four had remnant ovarian tissue (GCT-ROT). The results of the GnRH stimulation test were compared with those in six anestrous and six ovariectomized bitches. The most noteworthy results were as follows. The basal plasma LH concentrations of the GCT-ROT bitches were higher (P < 0.05) than those of the anestrous bitches. The increment in the plasma LH concentration after GnRH administration in the GCT-total bitches was lower (P < 0.001) than the increments in both the anestrous and ovariectomized bitches. The basal plasma estradiol concentrations in the GCT-total bitches were higher (P < 0.001) than those in the anestrous and ovariectomized bitches. In conclusion, the pituitary-ovarian axis is affected in bitches with a functional GCT and is characterized by relatively high plasma LH concentrations in GCT-ROT bitches and a subnormal LH response to GnRH stimulation in all GCT bitches compared with those in anestrous and ovariectomized bitches. The relatively high proportion of dogs with remnant ovarian tissue among the GCT bitches suggests a pathogenetic role for elevated gonadotropin secretion in the pathogenesis of GCT.

Hypothalamic deafferentation in prepuberal beef heifers: Effects of gonadotropin-releasing hormone and estradiol benzoate on luteinizing hormone secretion

Hypothalamic control of luteinizing hormone (LH) secretion was investigated in crossbred beef heifer calves by comparing anterior (AHD), posterior (PHD), and complete (CHD) hypothalamic deafferentation with sham operated controls (SOC). Heifers ( n = 16) were fitted with an indwelling jugular catheter for 6 days before cranial surgery, and assigned randomly to treatments. Blood for radioimmunoassay of LH was collected sequentially at 15-min intervals during an 8-h period on days − 1 before and day 6 after hypothalamic deafferentation or sham operation. On the day of surgery, blood samples were collected sequentially at 15-min intervals 2 h before induction of anesthesia and throughout surgery and early recovery. Seven months after hypothalamic deafferentation, all experimental and sham operated heifers were ovariectomized and treated with vegetable oil (i.m.) plus saline (i.v.), vegetable oil plus gonadotropin releasing hormone (GnRH), estradiol benzoate (EB, 1 mg) in vegetable oil. After ovariectomy basal plasma concentrations of LH increased ( P < 0.01) compared with the low circulating hormone levels before ovariectomy. The amplitude of LH response to GnRH was greater ( P < 0.01) in CHD and PHD when compared with SOC and AHD heifers. Injection of EB failed to induce a LH surge in CHD and PHD 900–1100 min later when compared with the robust response seen in SOC and AHD heifers. Injection of EB plus GnRH elicited LH release in all deafferentated and sham operated heifers. These results indicate a transient change in LH secretion after AHD or CHD in prepuberal heifers with intact ovaries. After OVX, the integrity of the neural connection of the posterior hypothalamus is required for EB-induced LH release in beef heifers.

Pulsatile plasma profiles of FSH and LH before and during medroxyprogesterone acetate treatment in the bitch

The aim of this study was to investigate the effect of medroxyprogesterone acetate (MPA) on pulsatile secretion of gonadotropins in the bitch. Five intact Beagle bitches were treated with MPA in a dose of 10mg/kg body weight subcutaneously at intervals of 4 weeks for a total of 13 injections, starting during anestrus. The 6-h plasma profiles of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined before, and 3, 6, 9, and 12 months after the start of MPA treatment. After 6 months of MPA treatment basal plasma LH concentration was transiently increased significantly. Basal plasma FSH concentration and the area under the curve above the zero level (AUC0) for FSH were significantly higher after 3 months of MPA treatment than before or after 9 and 12 months of treatment. MPA treatment did not significantly affect pulse frequency, pulse amplitude, or AUC above the baseline for either LH or FSH. During treatment 58 significant LH pulses were identified, and although each LH pulse coincided with an increase in plasma FSH concentration, in 17 cases the amplitude of the increase was too small to be recognized as a significant FSH pulse. In conclusion, MPA treatment did not suppress basal plasma gonadotropin levels in the bitches. On the contrary, it caused a temporary rise in the basal concentration of both FSH and LH, which may have been due to a direct effect of MPA on the ovary. In addition, several LH pulses were not accompanied by a significant FSH pulse, suggesting that MPA treatment attenuated the pulsatile pituitary release of FSH.

Pituitary luteinizing hormone responses to single doses of exogenous GnRH in female social Cape ground squirrels exhibiting low reproductive skew

AbstractThe Cape ground squirrel Xerus inauris is unusual among social mammals as it exhibits a low reproductive skew, being a facultative plural breeder with not all females breeding within a group. We investigated pituitary function to assess whether there was reproductive inhibition at the level of the pituitary and potentially the hypothalamus in breeding and non‐breeding female Cape ground squirrels. We did so during the summer and winter periods by measuring luteinizing hormone (LH) responses to single doses of 2 g exogenous gonadotropin‐releasing hormone (GnRH) and physiological saline administered to 42 females from 11 colonies. Basal LH concentrations of females increased in response to the GnRH challenge. Basal plasma LH concentrations were greater during winter, when most oestrus events are observed. However, we found no differences in plasma LH concentrations between breeding and non‐breeding females. We showed that the anterior pituitary of non‐breeding female ground squirrels is no less sensitive to exogenously administered GnRH than that of breeding females. We therefore concluded that the pituitary is no more active in breeding than non‐breeding females. The lack of differentiation in response to GnRH suggests that either non‐breeding females have ovaries that are less sensitive to LH or that they refrain from sexual activity with males through an alternative mechanism of self‐restraint.

Basal and GnRH-induced secretion of FSH and LH in anestrous versus ovariectomized bitches

The basal and gonadotropin releasing hormone (GnRH)-induced plasma concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) were studied in four anestrous and four ovariectomized (OVX) bitches. Blood samples were obtained via jugular venipuncture 40 min before and 0, 10, 20, 30, 60, 90, and 120 min after the i.v. administration of synthetic GnRH in a dose of 10 μg/kg body weight. The basal plasma FSH and LH concentrations were significantly higher in the OVX bitches than in the anestrous bitches. In the anestrous bitches, the plasma FSH concentration was significantly higher than the pretreatment level at 10, 20, and 30 min, whereas the plasma LH concentration was significantly elevated at 10 and 20 min. The maximal GnRH-induced plasma FSH concentration in the anestrous bitches did not surpass the lowest plasma FSH concentration in the OVX bitches, whereas the GnRH-induced plasma LH concentrations in the anestrous bitches overlapped with the basal plasma LH concentrations in the OVX bitches. In the OVX bitches, GnRH administration did not induce a significant change in the plasma FSH concentration, whereas the plasma LH concentration increased significantly at 10 and 20 min. In conclusion, the results of the present study indicate that in anestrous bitches GnRH challenge results in increased plasma levels of both FSH and LH, whereas in the OVX bitches, in which the basal plasma FSH and LH concentrations are higher, only a rise in the plasma LH concentration is present after GnRH stimulation. The results also suggest that a test to measure plasma concentration of FSH in single samples appears to have potential in verification of neuter status in bitches.

Seasonal Differences in the Parameters of Luteinizing Hormone Release to Exogenous Gonadotropin Releasing Hormone in Prepubertal Holstein Heifers in Sapporo

Stress due to summer heat has adverse effects on reproduction in Holstein dairy cattle. Summer suppression of reproduction of Holsteins can pose an important economic problem, even in Hokkaido prefecture located in the northern region of Japan. Hokkaido is one of the most important dairy farming areas of Japan. This study is an attempt to clarify the seasonal differences in the parameters of luteinizing hormone (LH) response to exogenous gonadotropin releasing hormone (GnRH) in Sapporo, Hokkaido, Japan. A total of 12 prepubertal heifers received an injection with GnRH analogue intramuscularly in either May (n=4, May group), July (n=4, July group), or November (n=4, November group), and serial blood samples were collected to analyze the parameters of the LH response curve after GnRH injection. The parameters were as follows: the basal LH concentration, peak LH concentration, duration from the time of GnRH injection to the time of the peak LH concentration, and area under the LH response curve (AUC). There were no significant differences in the basal and peak LH concentrations or the AUC among the three groups. The July group reached the LH peak significantly (P<0.05) faster than the May group, but there was no significant difference with the November group. Therefore, the results of the present study do not demonstrate an effect of summer heat on the LH response to the exogenous GnRH in Holstein heifers.

Photoperiod and luteinizing hormone secretion in domestic and wild pigs

During seasonal anoestrus (long-days), oestradiol can effectively inhibit the pulsatile secretion of luteinizing hormone (LH) in sheep. The aim of our trial was to determine whether the same regulatory mechanism exists in the pig. Altogether, 20 ovariectomized and oestradiol-implanted gilts (16 domestic pigs, 4 European wild boars) were randomly allocated to two treatment groups. The first group was kept under a short-day light–dark cycle of 8L:16D, and the second group under a long-day light regime of 16L:8D. After a 6-week treatment period, blood samples were taken at 20-min intervals for 12 h. After sampling, the light regimens were switched. Sampling was then repeated following another 6 weeks of treatment. In both treatment groups, 2.3 LH pulses occurred every 12 h. The basal LH level was 0.7 ± 0.4 ng/ml for the short-day group and 1.0 ± 0.5 ng/ml for the long-day group. The mean LH level was 0.9 ± 0.4 and 1.3 ± 0.6 ng/ml and the LH pulse amplitude 0.5 ± 0.4 and 0.6 ± 0.5 ng/ml, respectively. The basal and mean LH levels were therefore lower in short-day gilts ( P < 0.05), while LH pulse amplitude and frequency remained unaffected by treatment. In conclusion, the 6-week period under two different light regimes resulted in higher basal LH concentration in long-day gilts but was not able to produce changes in LH frequency in prepubertal gilts.

Effects of Gonadotrophin Releasing Hormone Administration on the Pituitary‐Ovarian Axis in Anoestrous vs Ovariectomized Bitches

The aim of this study was to determine the effects of gonadotrophin releasing hormone (GnRH) administration on the plasma concentrations of reproductive hormones in intact and ovariectomized (OVX) bitches. Therefore, blood samples were collected at multiple times before and after the administration of 10 microg/kg GnRH (Fertagyl)) for the determination of the plasma concentrations of luteinizing hormone (LH), oestradiol, progesterone and testosterone in six anoestrus and in six OVX bitches. The mean plasma LH concentrations before and 60 min after GnRH administration were significantly lower in the anoestrous bitches than in the OVX bitches. In both groups GnRH administration resulted in a significant increase in the plasma LH concentration. The highest plasma LH concentrations were found at 10 min after GnRH administration and these values did not differ significantly between the two groups. Only in the anoestrous bitches a significant increase in plasma oestradiol concentrations was found after GnRH administration and these values were significantly higher than those in the OVX bitches. The plasma concentrations of progesterone and testosterone were low (close to or below the limit of quantitation) both before and after GnRH administration and the differences between anoestrous and OVX bitches were not significant. It can be concluded that (i) basal plasma LH concentration is significantly higher in OVX bitches than in anoestrous bitches, (ii) plasma LH concentration increases after GnRH administration in both anoestrous and OVX bitches, (iii) GnRH administration causes a significant rise in plasma oestradiol concentration only if ovarian tissue is present and (iv) measurement of plasma progesterone and testosterone concentrations before and after GnRH administration does not aid in distinguishing between anoestrous and OVX bitches. The results of this study may provide a basis for the diagnosis of remnant ovarian tissue and verification of neuter status in the bitch.

LH responses to single doses of exogenous GnRH in the Cape mole rat (Georychus capensis): the pituitary potential for opportunistic breeding

AbstractThe Cape mole rat Georychus capensis is a solitary mole rat that inhabits the winter rainfall region of the Western Cape Province of South Africa. Circulating basal concentrations of luteinizing hormone (LH) were found to be significantly higher in the breeding season in both sexes. During both the breeding and non‐breeding season, administration of exogenous gonadotropin‐releasing hormone (GnRH) increased circulatory LH levels. The magnitude of the LH response to an overdose of exogenous GnRH both in and out of the breeding season in males and females was not significantly different. Typically, seasonally breeding species exhibit a down‐regulation of the pituitary and reproductive functions out of the breeding season. It appears that there is no down‐regulation of GnRH receptors at the level of the pituitary out of the breeding season, because the pituitary responds to an exogenous GnRH challenge equally both in and out of the breeding period. The Cape mole rat exhibits the potential for opportunistic breeding out of the breeding period, provided that environmental factors are favourable. This finding questions whether this mole rat is actually a seasonal breeder or whether reproduction is hindered by the ecological constraint of the lack of opportunities to burrow and find mates at certain times of the year.