Increase In Luteinizing Hormone Concentrations Research Articles

NEURO-ENDOCRINE ASPECTS OF INFERTILITY IN WOMEN WITH LONG-COVID-19

Currently, the exact mechanisms of the impact of COVID-19 on women's reproductive health remain poorly defined. Purpose of the study is to assess the hormonal function of patients with infertility and long-term COVID-19. Materials and methods. The main group consisted of 80 women with infertility who had symptoms of "long-COVID", the comparison group - 40 patients without a history of COVID-19. Hormonal studies of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, melatonin, estradiol (E2), progesterone (P), free testosterone (Tf), dehydroepiandrosterone (DHEA), cortisol, anti-Müllerian hormone (AMH) were conducted. Results. Violation of gonadotropic regulation of reproductive function is manifested by an increase in the serum concentration of LH and FSH and an increase in their ratio. A tendency to hyperprolactinemia, a relative decrease in serum melatonin was revealed. A more than 2-fold increase in the E2/P ratio on the 22nd day of the menstrual cycle indicates a tendency to hyperestrogenemia. An increase in the level of serum androgens (Tf and DHEA), which also play a role in female reproduction, was detected. Elevated levels of the stress hormone cortisol can negatively affect the chances of getting pregnant in assisted reproductive technologies programs. A decrease in AMH was observed in patients with infertility and long-term COVID-19, indicating a decrease in their ovarian reserve. Conclusion. The identified neuro-endocrine changes in patients with infertility and long-term COVID-19, due to the direct and indirect effects of the transmitted disease and its consequences, may be a marker of reduced reproductive potential and unsuccessful attempts to use assisted reproductive technologies.

Involvement of somatotrophic hormones in the postpartum regulation of ovarian activity in mares

Mares resume ovarian activity rapidly after foaling. Besides follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the pituitary synthesizes prolactin and growth hormone which stimulate insulin-like growth factor (IGF) synthesis in the liver. We tested the hypothesis that follicular growth is initiated already antepartum, mares with early and delayed ovulation differ in IGF-1 release and that there is an additional IGF-1 synthesis in the placenta. Plasma concentrations of LH, FSH, IGF-1, IGF-2, activin and prolactin. IGF-1, IGF-2, prolactin and their receptors in placental tissues were analyzed at the mRNA and protein level. Follicular growth was determined from 15 days before to 15 days after foaling in 14 pregnancies. Mares ovulating within 15 days postpartum formed group OV (n=5) and mares not ovulating within 15 days group NOV (n=9). Before foaling, follicles with a diameter >1 cm were present in all mares and their number increased over time (p<0.05). Follicle growth after foaling was more pronounced in OV mares (day p<0.001, group p<0.05, day x group p<0.05) in parallel to an increase in LH concentration (p<0.001, day x group p<0.001) while FSH increased (p<0.001) similarly in both groups. Plasma concentrations of IGF-1 and prolactin peaked one day after foaling (p<0.001). The IGF-1 mRNA abundance was higher in the allantochorion but lower in the amnion of OV versus NOV mares (group p=0.01, localization x group p<0.01). The IGF-1 receptor mRNA was most abundant in the allantochorion (p<0.001) and IGF-1 protein was expressed in placental tissue without differences between groups. In conclusion, follicular growth in mares is initiated before foaling and placental IGF-1 may enhance resumption of ovulatory cycles.

THE ROLE OF LUTEINIZING HORMONE (LH) RECEPTOR IN THE REGULATION OF OOCYTE MATURATION: A SYSTEMATIC LITERATURE REVIEW

The hormone luteinizing hormone (LH) is an important glycoprotein hormone that controls the activity of the gonadal organs, which in turn affects the physiology of the menstrual cycle. For LH to exert its effects, its specific receptor (LHR) must be expressed by cumulus cells. Objective: To determine the role of LH receptors (Luteinizing Hormone) in the regulation of human oocyte maturation processes Method:Systematic Literature Review (SLR). Data collection was conducted by documenting all articles based on predefined inclusion and exclusion criteria. A total of 10 national and international journal articles were retrieved from databases such as Google Scholar, PubMed, and Science Direct, using specific keywords related to the role of LH receptors and oocyte maturation. The literature search and study selection process followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Results:The highest expression of Luteinizing Hormone Receptor (LHR) observed in preovulatory follicles. Cumulus cell maturation, covering 100% of the oocytes, was 74%. FSHR and LHR mRNA expression levels increased with an increase in LH concentration in the in vitro maturation (IVM) medium. After 24 hours of IVM, there was a significant downregulation in the expression of LHR and FSHR.The mRNA and protein levels of FSHR and LHR in the cumulus-oocyte complex gradually decreased with increasing doses of FRBI in the IVM media compared to the control group. Majority of the cumulus cells from MII oocytes had RGS2/B2M gene expression of more than 50%. LH receptor expression in granulosa cells positively correlated with morphology, oocyte maturity, and fertility rate in the poor responder group. Granulosa cells from an agonist-triggered cycle with recombinant human chorionic gonadotropin (rhCG) for 24 hours were observed to increase viability, regulate mRNA expression of 3β-HSD, LH receptor, VEGF, and BCL-L2. More than 50% of the oocytes are matured after hCG injectionat an hCG concentration of 119.8 mIU/mL. Conclusion:LH needs receptor binding and expression for proper function, resulting in improved oocyte maturation with optimal LHR concentration which is 10 µg/mL LH. LHR expression is highest in preovulatory follicles. LHR expression increases during antral follicle growth. Supplementing media with hCG improves oocyte maturity with a 77 mIU/mL cutoff value. Supplementation with FRBI reduce LHR expression in COCs. The number of cumulus cells can also indicate the level of oocyte maturity, where cumulus cells covering 100% of the oocytes show the highest oocyte maturation.

Factors Associated With Circulating Sex Hormones in Men : Individual Participant Data Meta-analyses.

Various factors modulate circulating testosterone in men, affecting interpretation of testosterone measurements. To clarify factors associated with variations in sex hormone concentrations. Systematic literature searches (to July 2019). Prospective cohort studies of community-dwelling men with total testosterone measured using mass spectrometry. Individual participant data (IPD) (9 studies; n= 21 074) and aggregate data (2 studies; n= 4075). Sociodemographic, lifestyle, and health factors and concentrations of total testosterone, sex hormone-binding globulin (SHBG), luteinizing hormone (LH), dihydrotestosterone, and estradiol were extracted. Two-stage random-effects IPD meta-analyses found a nonlinear association of testosterone with age, with negligible change among men aged 17 to 70 years (change per SD increase about the midpoint, -0.27 nmol/L [-7.8 ng/dL] [CI, -0.71 to 0.18 nmol/L {-20.5 to 5.2 ng/dL}]) and decreasing testosterone levels with age for men older than 70 years (-1.55 nmol/L [-44.7 ng/dL] [CI, -2.05 to -1.06 nmol/L {-59.1 to -30.6 ng/dL}]). Testosterone was inversely associated with body mass index (BMI) (change per SD increase, -2.42 nmol/L [-69.7 ng/dL] [CI, -2.70 to -2.13 nmol/L {-77.8 to -61.4 ng/dL}]). Testosterone concentrations were lower for men who were married (mean difference, -0.57 nmol/L [-16.4 ng/dL] [CI, -0.89 to -0.26 nmol/L {-25.6 to -7.5 ng/dL}]); undertook at most 75 minutes of vigorous physical activity per week (-0.51 nmol/L [-14.7 ng/dL] [CI, -0.90 to -0.13 nmol/L {-25.9 to -3.7 ng/dL}]); were former smokers (-0.34 nmol/L [-9.8 ng/dL] [CI, -0.55 to -0.12 nmol/L {-15.9 to -3.5 ng/dL}]); or had hypertension (-0.53 nmol/L [-15.3 ng/dL] [CI, -0.82 to -0.24 nmol/L {-23.6 to -6.9 ng/dL}]), cardiovascular disease (-0.35 nmol/L [-10.1 ng/dL] [CI, -0.55 to -0.15 nmol/L {-15.9 to -4.3 ng/dL}]), cancer (-1.39 nmol/L [-40.1 ng/dL] [CI, -1.79 to -0.99 nmol/L {-51.6 to -28.5 ng/dL}]), or diabetes (-1.43 nmol/L [-41.2 ng/dL] [CI, -1.65 to -1.22 nmol/L {-47.6 to -35.2 ng/dL}]). Sex hormone-binding globulin was directly associated with age and inversely associated with BMI. Luteinizing hormone was directly associated with age in men older than 70 years. Cross-sectional analysis, heterogeneity between studies and in timing of blood sampling, and imputation for missing data. Multiple factors are associated with variation in male testosterone, SHBG, and LH concentrations. Reduced testosterone and increased LH concentrations may indicate impaired testicular function after age 70 years. Interpretation of individual testosterone measurements should account particularly for age older than 70 years, obesity, diabetes, and cancer. Medical Research Future Fund, Government of Western Australia, and Lawley Pharmaceuticals. (PROSPERO: CRD42019139668).

Sex Dependent Action of Aroclor 1254 on Basal and sGnRHa-Stimulated Secretion of LH from the Pituitary Cells of Common Carp, Cyprinus carpio L.

Abstract Polychlorinated biphenyls (PCBs) affect the hypothalamic-pituitary-gonadal axis in many vertebrates, changing the hormonal regulation of reproduction. To identify one of the possible sites of action of PCBs on gonadotropin release in common carp, the direct effects of Aroclor 1254 on luteinizing hormone (LH) secretion from dispersed pituitary cells were investigated. Pituitary cells were obtained from sexually mature male and female common carp (Cyprinus carpio L.) at the time of natural spawning. The cells were incubated with different concentrations of Aroclor 1254 (5, 10, 50 and 100 ng mL–1 medium) and/or salmon gonadotropin-releasing hormone analogue (sGnRHa) at a concentration of 10−8 M. LH levels were measured in the cultured medium by the ELISA method after 10 hours of cell incubation. Incubation of male pituitary cells in the presence of tested concentrations of Aroclor did not change the basal LH secretion to the media. In the female pituitary cell incubations Aroclor (5, 10 and 100 ng mL–1 medium) caused a significant increase in LH concentrations in comparison to control incubations. In the case of sGnRHastimulated LH secretion in incubations of cells of both sexes, all the concentrations of Aroclor significantly stimulated LH release and potentiated stimulatory effects of sGnRH analogue. These results indicate that endocrine disrupters, such as Aroclor 1254, may affect reproduction in fish, acting also directly on gonadotrophs at the level of the pituitary gland, changing LH secretion.

Long-term effect of neutering on plasma luteinising hormone concentration in cats.

The objectives of this study were to validate a commercially available luteinising hormone (LH) cat ELISA, to determine whether the increases in plasma LH concentration that occur after neutering are maintained throughout cats' lives and if other factors such as calendar seasons in both intact and neutered cats, and neutering age in neutered cats, influence plasma LH concentrations. Stored plasma samples from client-owned cats were used for the measurement of LH concentrations. Clinical data, including age, sex, age at neutering and medical history, were reviewed. Two populations were included in this study: (1) a senior and geriatric cat population (⩾9 years old), including 18 intact and 18 neutered cats matched for age, sex and month of sample collection; and (2) an adult cat population (2-8 years old), including 45 neutered cats. LH concentrations were measured using a commercially available feline ELISA. Senior and geriatric neutered cats had higher plasma LH concentrations than age-matched intact cats (P <0.001). Calendar season did not influence plasma LH concentrations in the adult (P = 0.727) or senior/geriatric (P = 0.745) cats included in this study. No influence of age at neutering was observed on plasma LH concentrations (P = 0.296). Neutering causes a significant long-term increase in LH concentrations in cats and further studies are required to determine the consequences on feline health.

Intravenous infusion of kisspeptin increased serum luteinizing hormone acutely and decreased serum follicle stimulating hormone chronically in prepubertal bull calves

Kisspeptin (KP) is a hypothalamic neuropeptide that stimulates the secretion of gonadotropin releasing hormone. To determine the acute and chronic effects of KP on serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH), prepubertal bull calves [12 ± 1 (SD) weeks of age; 96.5 ± 14.5 kg BW] were administered one of four treatments [0.0 (control; CON), 0.125 (L-KP), 0.25 (M-KP), or 0.5 (H-KP) μg of KP/kg BW/hour] by intravenous infusion for 76 h. Blood samples were collected every 15 min for the first (acute; 1–6 h; Day 1) and last (chronic; 71–76 h; Day 4) 6 h of the intravenous infusions. Serum concentrations of LH and FSH were determined by radioimmunoassay. For each day, effects of treatment, time, and interactions on LH and FSH concentrations and pulse parameters were analyzed using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was a treatment effect (P = 0.002) and a treatment × time interaction during Day 1 (P = 0.02) such that LH concentrations were greatest following administration of all doses of KP when compared to CON. However, there was no treatment effect (P = 0.57) or a treatment × time interaction during Day 4 (P = 0.20) on serum LH concentrations. There was a treatment by day interaction (P = 0.02) on mean serum FSH concentrations. Most notably, on Day 4 mean serum FSH concentrations during intravenous infusion of M-KP and H-KP doses were less than that of CON. There was a treatment by day interaction (P = 0.0054) on FSH pulse amplitude concentrations, such that intravenous infusion of all doses of KP on Day 4 decreased FSH pulse amplitudes. In conclusion, acute infusion of KP increased LH concentrations and chronic infusion of KP decreased FSH concentrations. Despite the potential suppression of the hypothalamic–pituitary–gonadal axis with chronic infusion of KP, there are likely applications of KP, KP analogs, or KP receptor agonists to hasten the onset of puberty in livestock.

Acute and subacute effects of a synthetic kisspeptin analog, C6, on serum concentrations of luteinizing hormone, follicle stimulating hormone, and testosterone in prepubertal bull calves

Kisspeptin (KP) is a neuropeptide integral in regulating puberty and gonadotropin releasing hormone. Compound 6 (C6), a KP analog, is more potent in vitro, has a longer half-life, and may have greater therapeutic applications than KP. To determine the acute and subacute effects of KP and C6 on serum concentrations of luteinizing hormone (LH), follicle stimulating hormones (FSH), and testosterone (T), prepubertal bull calves [12.1 ± 1.1 (SD) weeks of age; 91.2 ± 10.8 kg BW] were assigned to one of three treatment groups [Saline (n = 4), KP (n = 4; 20 nmoles), or C6 (n = 4; 20 nmoles). Treatments were administered intramuscularly once daily for four consecutive days. Blood samples were collected every 15 min for 6 h immediately following treatment administration on Day 1 (acute) and Day 4 (subacute). Serum concentrations of LH, FSH, and T were determined by radioimmunoassay. For each day, effects of treatment, time, and interactions on LH and FSH concentrations and pulse parameters were analyzed using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was a treatment × time interaction during Day 1 (P < 0.0001) and Day 4 (P = 0.02) such that LH concentrations were greatest following administration of C6 (albeit diminished during Day 4). Number of LH pulses were least (P = 0.02) and LH nadirs were highest (P = 0.04) following administration of C6 (P = 0.02). There was no effect of treatment (P = 0.95) or treatment × time interaction (P = 0.10) on serum FSH concentrations during Day 1. During Day 4 FSH concentrations (P = 0.02) and number of FSH pulses (P = 0.02) were least following administration of C6. There was no effect of treatment (P = 0.33), time (P = 0.19) or treatment × time interaction (P = 0.44) on T concentrations. In conclusion, acute and subacute C6 increased LH concentrations and subacute C6 decreased FSH concentrations and pulse parameters. Despite suppression of FSH with subacute daily administration of C6, altered frequency and timing of treatment with KP analogs may have application to affect the onset of puberty in livestock.

The Two Populations of Kisspeptin Neurons Are Involved in the Ram-Induced LH Pulsatile Secretion and LH Surge in Anestrous Ewes.

Exposure to a ram during spring stimulates luteinizing hormone (LH) secretion and can induce ovulation in sexually quiescent ewes ("ram effect"). Kisspeptin (Kiss) present in the arcuate nucleus (ARC) and the preoptic area (POA) is a potent stimulators of LH secretion. Our aim was to investigate whether Kiss neurons mediate the increase in LH secretion during the ram effect. With double immunofluorescent detection, we identified Kiss neurons (Kiss IR) activated (Fos IR) by exposure to a ram for 2 hours (M2) or 12 hours (M12) or to ewes for 2 hours (C). The density of cells Kiss + Fos IR and the proportion of Kiss IR cells that were also Fos IR cells were higher in M2 and M12 than in C in ARC (P < 0.002) and POA (P < 0.02). In ARC, these parameters were also higher in M12 than in M2 (P < 0.02 and P < 0.05). Kiss antagonist (P234 10-6M) administered by retrodialysis in POA for 3 hours at the time of introduction of the ram reduced the amplitude of the male-induced increase in LH concentration compared with solvent (P < 0.02). In ARC, P234 had a more limited effect (P < 0.038 1 hour after P234) but pulse frequency increased less than after solvent (P = 0.07). In contrast, Kiss antagonist (P271 10-4M) infused in ARC but not POA 6 to 18 hours after introduction of the ram prevented the LH surge in the ewe (0/6 vs 4/5 and 4/6 in C). These results suggest that both populations of Kiss neurons are involved in the ram-induced pulsatile LH secretion and in the LH surge.

Age-related alterations in hypothalamic kisspeptin, neurokinin B, and dynorphin neurons and in pulsatile LH release in female and male rats

Pulsatile secretion of gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) decreases during aging. Kisspeptin (encoded by Kiss1) neurons in the arcuate nucleus coexpress neurokinin B (Tac3) and dynorphin (Pdyn) and are critical for regulating the GnRH/LH pulse. We therefore examined kisspeptin neurons by histochemistry and pulsatile LH release in rats aged 2–3 (Young), 12–13 (Young-Middle), 19–22 (Late-Middle), and 24–26 (Old) months. Total LH concentrations, sampled for 3 hours, decreased in both sexes with aging. In females, numbers of Tac3 and Pdyn neurons were significantly reduced in all aging rats, and numbers of Kiss1 neurons were significantly reduced in Late-Middle and Old rats. In males, numbers of all 3 neuron-types were significantly decreased in all aging rats. GnRH agonist induced LH release in all animals; however, the increased LH concentration in all aging rats was less than that in Young rats. These results suggest that expression of each gene in kisspeptin neurons may be controlled individually during aging, and that reduction of their expression or change in pituitary responsiveness may cause attenuated pulsatile LH secretion.

Metabolic and Endocrine Characteristics of Indian Women with Polycystic Ovary Syndrome.

Polycystic ovary syndrome (PCOS) is one of the most common endocrinological disorders among women of reproductive age and the leading cause of female infertility. This study intends to evaluate the lipid profile, hormonal levels [free T3 (fT3), free T4 (fT4), thyroid stimulating hormone (TSH), insulin, luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin] in PCOS women from Nellore and its surrounding districts of Andhra Pradesh, India. This cross-sectional study included 80 newly diagnosed PCOS women and an equal number of age and body mass index (BMI) matched healthy controls. We used the photometry methods to determine serum glucose levels and the lipid profile. An immunoturbidometry method was employed to measure high sensitive C-reactive protein (hsCRP). All hormonal parameters were measured using chemiluminescence immunoassays. Insulin resistance was evaluated using the homeostatic model assessment-insulin resistance (HOMA-IR) method. Statistical analysis was done using SPSS software version 20.0. The PCOS patients presented statistically higher levels of total cholesterol (TC), triglycerides (TG) and low density lipoprotein cholesterol (LDL-c, P<0.0001) when compared to those of controls. PCOS patients had elevated fasting glucose, hsCRP, fasting insulin, TSH, LH and prolactin levels (P<0.001). An increased LH/FSH ratio (>1.5) was seen in women with PCOS compared with control women. In addition, we observed a direct correlation between fasting insulin with fasting glucose and HOMA-IR. LH was inversely proportional to BMI. The present study showed a higher prevalence of insulin resistance, dyslipidemia, and hypothyroidism in PCOS women. Furthermore this study showed increased LH concentrations, a higher LH/FSH ratio, and higher prolactin levels in PCOS women.

Different types of opioid receptors involved in the suppression of LH secretion in lactating sheep

To learn the involvement of endogenous opioid peptides (EOP) in the regulation of reproductive activity in ruminants, the effects of different opioid antagonists on luteinizing hormone (LH) secretion were determined in sheep during the early stage of lactation. The opioid receptor antagonists: naloxone (all types of receptors, n=5), naloxonazine (μ receptor, n=5), GNTI- (κ receptor, n=5), naltrindole (δ receptor, n=5) or the vehicle (control, n=5) were infused intracerebroventricularly in a series of five 30-min infusions (60μg/60μl) at 30-min intervals. The period of the experiment included the non-suckling (10:00–12.30) and suckling (12.30–15.00) periods. Blood samples were collected from 10.00 to 15.00 at 10-min intervals, and plasma LH concentration was assayed by the radioimmunoassay method. The obtained results showed that blocking of the EOP action within the central nervous system in lactating sheep caused a significant (p<0.001) increase in LH concentration in all treated groups, in comparison to the control. In the naloxone-treated group, a significant (p<0.05) increase in LH secretion also occurred during suckling. The amplitude of LH pulses increased significantly in the naloxonazine- (p<0.01) and naltrindole- (p<0.05) treated ewes compared to the control; there were no significant differences in the frequency of LH pulses among the groups. In conclusion, our study indicates that EOP play a crucial role in the mechanism inhibiting GnRH/LH axis activity in lactating sheep and that the ligands for μ opioid receptor may have the highest inhibitory effect.

Central Administration of Neurokinin B Activates Kisspeptin/NKB Neurons in the Arcuate Nucleus and Stimulates Luteinizing Hormone Secretion in Ewes During the Non-Breeding Season

Human genetic studies have suggested that kisspeptin and neurokinin B (NKB) play pivotal roles in the control of gonadotropin-releasing hormone (GnRH) secretion. However, the role of NKB in this context is less clear compared with that of kisspeptin. In the present study, we investigated the ratio of colocalization of kisspeptin and NKB in neurons in the arcuate nucleus (ARC), the effects of intracerebroventricular infusion of NKB on luteinizing hormone (LH) secretion and whether the treatment activates ARC kisspeptin/NKB neurons in seasonally anestrous ewes. Double-labeling immunohistochemistry revealed that the majority of kisspeptin neurons coexpressed NKB in the ARC. Infusion of NKB for 2 h into the lateral ventricle elicited a discharge of LH, which resulted in significant increases in LH concentrations between 20 and 50 min after the start of infusion compared with a saline-infused control. Animals were sacrificed immediately after the end of infusion, and Fos expression in ARC kisspeptin neurons was immunohistochemically examined. The NKB treatment activated kisspeptin neurons throughout the ARC, and approximately 70% of kisspeptin neurons expressed Fos immunoreactivity at the caudal portion of the nucleus. The present study demonstrated that a central infusion of NKB elicited a discharge of LH, which was associated with the activation of a large population of ARC kisspeptin/NKB neurons in seasonally anestrous ewes. The results suggest that NKB plays a stimulatory role in the control of pulsatile GnRH secretion and that the population of ARC kisspeptin/NKB neurons is one of sites of the NKB action in sheep.

The Role of Nutrition in the Regulation of Luteinizing Hormone Secretion by the Opioidergic, Dopaminergic, and Serotonergic Systems in Female Mediterranean Goats1

This study examined which neural mechanism (opioid, dopaminergic, or serotonergic system) is involved in the regulation of luteinizing hormone (LH) secretion, with and without nutritional modulation, at different times of the photoperiodic cycle. Goats were randomly distributed into two experimental groups that received either 1.1 (high group; n = 18) or 0.7 (low group; n = 18) times the nutritional maintenance requirements. The goats were exposed to alternations of 3 mo of long days and 3 mo of short days. Plasma LH concentrations were measured twice a week. The effects of intravenous injections of naloxone (endogenous opioid receptor antagonist), pimozide (dopaminergic(2) receptor antagonist), and cyproheptadine (serotonin 5-hydroxytryptamine(2) receptor antagonist) on LH secretion were assessed during challenges in three different photoperiodic situations: the onset of LH stimulation by short days (OnsetSD), the onset of LH inhibition by long days (OnsetLD), and during the LH inhibition by long days (LateLD). The role of the different neural systems was clearly modified by the level of nutrition. In the low-nutrition group, only naloxone increased LH concentrations during onsetLD (P < 0.05). However, in the high-nutrition group, naloxone increased the concentration and pulsatility of LH (P < 0.05) in onsetSD and onsetLD. Pimozide increased LH concentration and pulsatility (P < 0.05) in onsetLD and LH concentration in lateLD (P < 0.001). Finally, cyproheptadine significantly increased LH concentration at all three times (P < 0.001). These results provide evidence that all three systems are involved in the inhibition of LH release in onsetLD, and that the opioid and serotonin mechanisms are involved during the onsetSD that were enhanced by a high plane of nutrition.

Neuroendocrine Effects of Androgens in Adult Polycystic Ovary Syndrome and Female Puberty

In addition to hyperandrogenism and ovulatory dysfunction, polycystic ovary syndrome (PCOS) is characterized by neuroendocrine abnormalities including a persistently rapid gonadotropin-releasing hormone (GnRH) pulse frequency. Rapid GnRH pulsatility favors pituitary secretion of luteinizing hormone (LH) over that of follicle-stimulating hormone (FSH). Excess LH stimulates ovarian androgen production, whereas relative deficits in FSH impair follicular development. The rapid GnRH pulse frequency is a result of reduced progesterone-mediated feedback inhibition of the GnRH pulse generator secondary to infrequent luteal phase increases in progesterone, as well as reduced hypothalamic sensitivity to progesterone feedback. Progesterone sensitivity is restored by treatment with the androgen receptor blocker flutamide. As such, hyperandrogenemia appears to play an important pathophysiologic role in PCOS. Adolescent hyperandrogenemia is believed to be a precursor to adult PCOS. In addition to increased LH concentrations and pulse frequency, some girls with elevated androgen levels also demonstrate reduced hypothalamic sensitivity to progesterone feedback. We hypothesize that excess peripubertal androgens may reduce the sensitivity of the GnRH pulse generator to sex steroid inhibition in susceptible individuals, resulting in increased GnRH pulse frequency and subsequent abnormalities in gonadotropin secretion, ovarian androgen production, and ovulatory function. Over time, these abnormalities may progress to the clinical hyperandrogenism and chronic oligo-ovulation typical of adult PCOS.

Development and validation of a simple, sensitive, second antibody format enzyme immunoassay for LH determination in plasma

The objective of this study was to develop and validate a direct simple and highly sensitive enzyme immunoassay (EIA) for luteinizing hormone (LH) determination in buffalo plasma on microtiter plates using the biotin–streptavidin amplification system and the second antibody coating. Biotin was coupled to LH and used to bridge between streptavidin-peroxidase and immobilized antiserum in competitive assay. The EIA was carried out directly in 20 μl buffalo plasma. The LH standards ranging from 6.25 to 200 pg/well/20 μl were prepared in hormone free plasma collected from a buffalo on day 4 post-calving. The sensitivity of EIA procedure was 6.25 pg/well LH, which corresponds to 0.31 ng/ml plasma; the 50% relative binding sensitivity was seen at 50 pg/well/20 μl. Plasma volumes for the EIA, viz. 10 and 20 μl, did not influence the shape of standard curve even though a slight drop in the OD 450 was seen with higher plasma volumes. A parallelism was carried out to compare the endogenous buffalo plasma LH with bovine LH standards. For the biological validation of assay, 10 Murrah buffaloes were used. These were administered (10 μg im) with a synthetic analogue of gonadotropin-releasing hormone (GnRH) and blood samples were collected at 15-min interval using indwelling jugular catheter beginning just prior to GnRH injection till 6 h and thereafter 2-h interval for another 18 h. In all animals, sharp increases in LH concentrations were recorded post-GnRH administration, which confirms the biological validation of the EIA. To record the LH peak during periestrus in a cycling buffalo, the blood samples were collected at 2-h intervals from onset of behavioral estrus signs till ovulation. The LH peak was observed after the initial behavioural estrus signs followed by the gradual decline in the levels towards the ovulation.

Influence of Stimuli from Chicks on Behavior and Concentrations of Plasma Prolactin and Luteinizing Hormone in Incubating Hens

Removal of eggs from the nests of incubating birds or substitution of eggs for chicks disrupts incubation behavior and induces changes in the secretion of prolactin and luteinizing hormone (LH). The aim of the present study was to determine how different stimuli, such as physical contact with eggs and tactile, visual, and/or auditory cues from chicks, interact to control the transition between incubation and brooding and to induce changes in prolactin and LH plasma concentrations. Physical contact with chicks, in the presence or absence of eggs, induced brooding behavior and an immediate fall in plasma prolactin concentration and a gradual increase in LH concentration. Vocalizations, particularly clucking and food calls, increased rapidly while incubation and nest attachment disappeared slowly. No change in plasma prolactin or LH concentration was observed in incubating hens which could hear and see or only hear chicks. These incubating hens showed no interest in chicks and continued to incubate persistently. To conclude, tactile stimuli, alone or in combination with visual and/or auditory stimuli from newly hatched chicks, are the only cues that induce the transition from incubation to brooding and the associated decrease in prolactin secretion and increase in LH secretion.

Short-term stimulation of luteinizing hormone (LH) secretion by naloxone treatment in the pregnant gilt

An experiment was initiated to determine the involvement of endogenous opioids (EOP) in the modulation of luteinizing hormone (LH) secretion during two stages of pregnancy at 40 and 70 days in the pig. Twenty-four crossbred pregnant gilts (150 ± 10 kg) were given 1 mg kg −1 body weight (BW) of naloxone (NAL), or 3 ml saline i.v. at 40 days (NAL, n=6; saline, n=6) or at 70 days (NAL, n=6; saline, n=6) of pregnancy. Blood plasma was collected at 15 min intervals for 1 h before and 3 h after treatment with NAL or saline. Following this period, all NAL-treated gilts were given 1 μg kg −1 BW of gonadotropin releasing hormone (GnRH) in 3 ml saline i.v. and blood samples were collected every 15 min for 3 h. At 40 days of pregnancy, mean plasma LH concentrations were 0.22 ± 0.1 ng ml −1 for 1 h before NAL treatment. In five of the six treated pigs, the infusion of NAL increased LH concentration to 1.33 ± 0.5 ng ml −1 ( P < 0.05), 1.58 ± 0.42 ng ml −1 ( P < 0.01), and 1.28 ± 0.39 ng ml −1 ( P < 0.01) at 15 min, 30 min and 45 min, respectively. Concentrations of LH returned to control values by 90 min post-treatment. The control group values ranged from 0.15 ± 0.01 ng ml −1 to 0.37 ± 0.34 ng ml −1 1 h before to 3 h after saline administration. At 70 days of pregnancy, NAL did not alter plasma LH concentrations, although some increases were detected in individual gilts. Mean plasma LH concentrations were 0.16 ± 0.04 ng ml −1 for 1 h before NAL, and 0.61 ± 0.35 ng ml −1, 0.46 ± 0.27 ng ml −1 and 0.77 ± 0.29 ng ml −1 during the 1 h, 2 h and 3 h periods after NAL treatment, respectively. The infusion of GnRH increased ( P < 0.001) LH concentrations in both pregnancy periods. Significant changes in plasma progesterone concentrations were not observed. These results indicate that the opioids are stronger modulators of LH secretion at 40 days of pregnancy than later in pregnancy in the pig. It is possible that during the second half of pregnancy, an alternative control of the EOP system may exist.

Effects of the opioid antagonist naloxone on release of luteinizing hormone in mares during the anovulatory season.

To investigate an involvement of endogenous opioids in the regulation of circannual changes in reproductive activity, effects of the opioid antagonist naloxone on the concentration of immunoreactive and bioactive luteinizing hormone (LH) in plasma were measured in mares during the anovulatory season. Naloxone (0.5 mg/kg i.v.) caused a significant increase (P < 0.05) in immunoreactive as well as bioactive LH concentration in plasma. The amplitude of the increase in LH concentrations measured with an in vitro bioassay was more pronounced than the amplitude of the increase in LH secretion determined by radioimmunoassay. This indicates that although in seasonal anovulatory mares the bioactivity of LH in plasma is low, highly bioactive LH is present in the anterior pituitary and can be released by naloxone. The LH response to naloxone did not depend on the degree of ovarian follicular activity. It can be concluded that a tonic opioid inhibition of LH release is present in mares during at least part of the anovulatory season and that endogenous opioids seem to be involved in the regulation of seasonal reproductive activity in the horse. In contrast to the situation during the breeding season, the opioid systems regulating LH release are activated independently of luteal progesterone.

Coordinate Pattern of Secretion of Luteinizing Hormone and Testosterone in Mature Male Turkeys Under Continuous and Intermittent Photoschedules

Secretory patterns of luteinizing hormone (LH) and testosterone (T) were determined in sexually mature male turkeys housed under Continuous [14 h light (L):10 h dark (D), n = 3)] or Intermittent [8 × (1L:2D), n = 3] photoschedules. Jugular vein cannulas were implanted on Day 0 and serial blood samples were taken at 5-min intervals for 12 h on Day 3 and again 4 to 7 d later.Most increases in T concentration were preceded by an increase in LH concentration for both photoschedules. Treatment differences for overall mean T [1.77 ± .58 (SE) ng/mL], baseline T (.92 ± .30 ng/mL), T peak number (6.1 ±1.2 per 12 h), T peak amplitude (2.77 ± 1.70 ng/mL), or T peak length (79 ± 24 min) were not significant (P > .05). The number of LH peaks was greater in the Continuous than Intermittent group (11.7 ± .6 vs 6.8 ± 1.4 per 12 h, P < .05), but there were no treatment differences in overall mean LH (4.56 ± 2.09 ng/mL), baseline LH (4.10 ± 2.11 ng/mL), LH peak amplitude (2.80 ± .92 ng/mL), or LH peak length (15.9 ± 3.1 min). There were no differences in T or LH concentrations between the photo- and scotophases in the continuous group, and pulses of both were seen in both phases in both lighting treatments. It was concluded that minor differences in patterns of LH secretion may occur between Continuous and Intermittent stimulatory lighting treatments in sexually mature male turkeys.