Gonadorelin Research & Studies

In the last twenty years, we have witnessed an important evolution of bioanalytical approaches moving from conventional lab bench instrumentation to simpler, easy-to-use techniques to deliver analytical responses on-site, with reduced analysis times and costs. In this frame, affinity reagents production has also jointly advanced from natural receptors to biomimetic, abiotic receptors, animal-free produced. Among biomimetic ones, aptamers, and molecular imprinted polymers (MIPs) play a leading role. Herein, our motivation is to provide insights into the evolution of conventional and innovative analytical approaches based on chromatography, immunochemistry, and affinity sensing referred to as peptide hormones. Indeed, the analysis of peptide hormones represents a current challenge for biomedical, pharmaceutical, and anti-doping analysis. Specifically, as a paradigmatic example, we report the case of gonadorelin, a neuropeptide that in recent years has drawn a lot of attention as a therapeutic drug misused in doping practices during sports competitions.

The objective of this study was to assess the efficacy of a single intramuscular administration of gonadorelin to induce ovulation in queens in oestrus.

Different GnRH products are used for timed artificial insemination (AI) in postpartum dairy cows. Previous studies reported greater LH release and increased ovulation percentage for gonadorelin diacetate tetrahydrate compared with gonadorelin hydrochloride but pregnancies per AI (P/AI) were not evaluated. The objective, therefore, was to compare P/AI for cows treated with either gonadorelin hydrochloride or gonadorelin diacetate tetrahydrate before the first timed AI or resynchronized timed AI. Holstein cows (n = 3938) in a confinement dairy in northeast Missouri were assigned to weekly cohorts (n = 22) on the basis of calving date. Cows were treated with "Presynch Ovsynch" (PGF2α, 14 days; PGF2α, 14 days; GnRH, 7 days; PGF2α, 56 hours; GnRH, 16 hours; timed AI) so that the first timed AI was 70 to 76 days postpartum. The PGF2α was Lutalyse (5 mL; 25 mg; Zoetis). The GnRH product was either gonadorelin hydrochloride (2 mL; 100 μg; n = 1945) or gonadorelin diacetate tetrahydrate (2 mL; 100 μg; n = 1993) and alternated weekly for cows assigned to cohorts. There were first timed AI (n = 1790) and resynchronized timed AI (n = 2148) cows within each cohort. The resynchronization began 32 days after timed AI (GnRH, 6 days; ultrasound pregnancy diagnosis, 1 day; and then for nonpregnant cows: PGF2α, 56 hours; GnRH, 16 hours; timed AI). The trial was conducted from January to February 2012 (n = 1203) and July to October 2012 (n = 2735). Cows were fed a total mixed ration, milked thrice daily, and milk tested monthly for volume, somatic cell count (SCC), fat percentage, protein percentage, and milk urea nitrogen. Data were analyzed by fitting the binary response data to a generalized linear mixed model for repeated measures. There was no effect of the GnRH product (treatment) on P/AI (38.4 ± 1.2 vs. 35.7 ± 1.3; gonadorelin diacetate tetrahydrate vs. gonadorelin hydrochloride). Treatment interactions with parity, month of breeding, or insemination number were not significant. The first-service P/AI (38.8 ± 1.4%) was greater (P < 0.05) than the resynchronized P/AI (35.3 ± 1.3%). Cows inseminated in the summer had lesser P/AI (effect of month; P < 0.001) compared with cows inseminated in the winter. There was a decrease (P < 0.002) in timed AI conception for cows with a greater milk SCC and an increase (P < 0.003) in P/AI for cows with a greater milk protein percentage. In conclusion, the GnRH product did not affect P/AI for the first or resynchronized timed AI in an Ovsynch-based program. Other factors affected P/AI including service number (lesser for the second service or greater), month (lesser in summer months), SCC (lesser for cows with greater SCC), and milk protein percentage (greater for cows with greater protein percentage).

Analogs of gonadoliberin (GnRH) are widely used in cattle to synchronize estrus and to induce ovulation, as well as for the treatment of ovarian cysts. The aim of this study was to compare the plasma profiles of LH and progesterone and the follicular dynamics in response to the administration of gonadorelin, lecirelin, or buserelin at the dose recommended to induce ovulation. In addition, the biological response to a half dose of lecirelin was assessed. Twelve healthy Holstein female cows were divided into four sequence groups, according to a Latin square design and received the four treatments during the four periods of the study. Before each period, the estrous cycle was synchronized, and on Day 6 or 7 of the ensuing cycle, the time at which it was most likely to have a dominant follicle, 100 μg of gonadorelin, 25 μg of lecirelin, 50 μg of lecirelin, or 10 μg of buserelin was administered to the cows. Blood samples were regularly collected for up to 4 days after the GnRH administrations. The plasma LH response was evaluated for up to 6 hours after administration, and the plasma progesterone response and ovarian follicular dynamics were evaluated for up to 4 days. There was a significantly lower LH release after gonadorelin treatment compared to lecirelin at the doses of 25 or 50 μg and the buserelin treatment. The mean maximal LH concentration after gonadorelin treatment was 2.5 lower than after lecirelin or buserelin treatment and was reached 1 hour earlier. Four days after the GnRH administration (i.e., at Days 10-11 of the estrous cycle), the overall mean increase in plasma progesterone concentration was 70% and did not differ between the treatment groups. The percentage of disappearance of the dominant follicle (84.8% of ovulation and 4.3% of luteinization) after GnRH treatment was high (73%, 82%, 100%, and 100%, for gonadorelin, lecirelin at the doses of 25 and 50 μg, and buserelin, respectively) and did not differ between the GnRH treatments. The follicle disappearance was followed by the emergence of a synchronous follicle wave within 2 days in almost all the heifers. Altogether, our data show that the three GnRH analogs, at the doses indicated for the induction of ovulation or at a half dose for lecirelin, are almost equally effective to induce the disappearance of the dominant follicle at Day 6 to 7 of the estrous cycle.

To clarify the impact of body mass index (BMI) on luteinizing hormone (LH) secretion in response to gonadorelin (GnRH) stimulation testing in girls diagnosed with idiopathic central precocious puberty (ICPP).

Gonadotropin-releasing hormone analogues are generally regarded as safe drugs. Gonadorelin acetate has been widely used for the diagnosis of central precocious puberty, and life-threatening reactions to gonadorelin acetate are extremely rare. Herein, we described - to the best of our knowledge - the first pediatric case in which severe anaphylaxis was encountered after intravenous gonadorelin acetate administration. An 8-year-old girl who was diagnosed with central precocious puberty was receiving triptorelin acetate treatment uneventfully for 6 months. In order to evaluate the efficacy of the treatment, an LH-RH stimulation test with gonadorelin acetate was planned. Within 3 min after intravenous administration of gonadorelin acetate, she lost consciousness and tonic seizures began in her hands and feet. She was immediately treated with epinephrine, diphenhydramine, and fluids. Her vital signs recovered within 30 min. Based on the results, anaphylaxis should be anticipated and the administration of these drugs should be performed in a setting that is equipped to deal with systemic reactions.

Studies suggest that estrogen plays a contributing role in colorectal cancer. This project examined the preventive effects of raloxifene, a selective estrogen receptor modulator (SERM), and gonadorelin, an antiestrogenic drug, in female Apc(Min/+) mouse intestinal tumorigenesis. Six-week-old Apc(Min/+)mice were fed diet containing 1 ppm raloxifene or control diet. Gonadorelin (150 ng/mouse) was injected subcutaneously into one treatment group. Intestinal tumors were evaluated for tumor multiplicity and size. Mice treated with raloxifene and gonadorelin showed colon tumor inhibition of 80% and 75%, respectively. Both drugs significantly inhibited small intestinal tumor multiplicity and size (75%-65%, P < 0.0001). Raloxifene and gonadorelin showed significant tumor inhibition with 98% and 94% inhibition of polyps >2 mm in size. In mice fed with raloxifene or injected with gonadorelin, tumors showed significantly reduced proliferating cell nuclear antigen expression (58%-65%, P < 0.0001). Raloxifene treatment decreased β-catenin, cyclin D1, laminin 1β, Ccl6, and stem-like cells (Lgr 5, EpCAM, CD44/CD24), as well as suppressed inflammatory genes (COX-2, mPGES-1, 5-LOX,). Gonadorelin showed significant decrease in COX-2, mPGES-1, iNOS, and stem-like cells or increased NK cells and chemokines required for NK cells. Both drugs were effective in suppressing tumor growth albeit with different mechanisms. These observations show that either suppression of estrogen levels or modulation of estrogen receptor dramatically suppresses small intestinal and colonic tumor formation in female Apc(Min/+) mice. These results support the concept of chemoprevention by these agents in reducing endogenous levels of estrogen or modulating ER signaling.

The objective was to determine luteinizing hormone (LH) secretion and follicular dynamics in cattle following administration of 3 gonadorelin formulations that are commercially available in Canada. In experiment 1, nonlactating Holstein cows (n = 4 per group) were randomly assigned to receive 100 micrograms gonadorelin diacetate tetrahydrate, intramuscularly (C; Cystorelin, or FE; Fertagyl). Blood samples (for LH analysis) were collected 0, 1, 2, and 4 hours after treatment. In experiment 2, nonlactating Holstein cows (n = 10 per group) were randomly allocated to receive 100 micrograms gonadorelin, intramuscularly as follows: 2 mL of C; 1 mL of FE; or 2 mL of Factrel (FA, gonadorelin hydrochloride). Gonadorelin treatment was done on days 6 or 7 after ovulation and blood samples for LH analysis were collected at 0, 1, 2, 4, and 6 hours after treatment. Ovaries were examined by ultrasonography, twice daily, to detect ovulation. A replicate was conducted using only C (n = 10) or FE (n = 10); blood samples were collected at 0, 1, 2, 3, and 4 hours. In experiment 3, beef heifers (n = 10 per group) were randomly assigned to receive 1 of 3 GnRH gonadorelin treatments (as in the first phase of experiment 2) on days 6 or 7 after ovulation and blood samples were collected at 0, 0.5, 1, 1.5, 2, and 4 hours. In experiments 2 and 3, both mean and mean peak plasma LH concentrations were higher (P < 0.05) in cattle treated with C. The proportion of dominant follicles that ovulated was higher (P < 0.02) in Holstein cows treated with C than in those treated with FE or FA (18/19, 11/19, and 4/7, respectively), but there was no significant difference among the products in beef heifers (6/10, 6/10, and 4/10, respectively). No significant differences were found in the interval from treatment to the emergence of the next follicular wave. In summary, C induced a greater LH release and this resulted in a higher ovulatory rate in Holstein cows but not in beef heifers.

Two experiments were conducted with bulls administered norgestomet and gonadorelin to determine if the gonadorelin-induced release of testosterone could be developed into a biological assay for quality assurance of gonadorelin. Implants containing norgestomet (0 to 36 mg) reduced the episodic release (r = -.81; P < .05) and mean concentrations of testosterone (r = -.82; P < .05). Gonadoreline-induced testosterone release increased (r = .99; P < .05) with increasing dosage of gonadorelin (up to 5 micrograms) in norgestomet-implanted bulls (36 mg). Maximal testosterone was released (> sixfold increase) with 5 to 40 micrograms of gonadorelin. In summary, the gonadorelin-induced testosterone release in bulls administered a synthetic progestin is a sensitive (0.008 microgram per kg body weight for 5 micrograms of gonadorelin) biological assay with a rapid turnaround time for the confirmation of gonadorelin potency. Based on a per-kg-body-weight basis, the norgestomet-treated bull is the most sensitive biological assay model.

Gonadotropin-releasing hormone (GnRH), a decapeptide synthesized and released by the hypothalamus, regulates production and release of the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by the adenohypophysis. Parenterally administered GnRH was initially used diagnostically as a test of adenohypophyseal reserve of LH and FSH. Subsequently, native GnRH was used therapeutically to treat hypothalamic hypogonadal and infertility states in both men and women. Because of the low potency and short half-life of native GnRH, long-acting, potent analogs have been developed that suppress secretion of native pituitary gonadotropins, resulting in medical gonadectomy. When administered parenterally and, more recently, intranasally, these compounds are useful in the management of prostate and breast carcinoma, endometriosis and uterine leiomyomata, precocious puberty and nontumorous ovarian hyperandrogenic syndromes.