GnRH Agonist Buserelin Research Articles

Pharmacokinetics and pharmacodynamics of testosterone enanthate and dihydrotestosterone enanthate in non-human primates

The pharmacokinetics and pharmacodynamics of testosterone enanthate and dihydrotestosterone-enanthate were compared in orchidectomized cynomolgus monkeys (Macaca fascicularis) and in intact GnRH agonist-suppressed rhesus monkeys (Macaca mulatta). Following a single im injection of 32.8 mg testosterone enanthate or 32.7 mg dihydrotestosterone-enanthate, i.e. 23.6 mg of pure steroid, in the orchidectomized cynomolgus monkeys, serum testosterone and dihydrotestosterone levels rose to 400 and 800% of baseline, respectively, within 24 h. Androgen levels remained in that range for 3-5 days followed by a continuous decline until baseline values were attained after 4-5 weeks. The areas under the testosterone- and dihydrotestosterone-curves did not differ significantly 2290 +/- 340 (dihydrotestosterone-enanthate) vs 2920 +/- 485 (testosterone-enanthate) suggesting that similar amounts of steroid had been released from the respective ester preparation. Mean half-life estimates of the terminal elimination phase were 4 and 7 days for testosterone-enanthate and dihydrotestosterone-enanthate, respectively. In a second experiment rhesus monkeys received, at 4-weekly intervals, sc implantation of a biodegradable polylactic:polyglycolide rod loaded with the GnRH agonist buserelin. The last injection was given during week 20. GnRH agonist treatment suppressed serum bioactive LH, testosterone and dihydrotestosterone levels, testicular size, sperm production, and seminal carnitine content. The ejaculatory response to electrostimulation and the masturbatory behaviour were abolished. Testosterone or dihydrotestosterone injections at the same doses as above were given in week 10, 14, 17 and 20 of GnRH agonist treatment. Serum testosterone and dihydrotestosterone levels were stimulated 9- and 4-fold, respectively. Mean half-life estimates for testosterone-enanthate and dihydrotestosterone were 5 and 7 days, respectively. Both ester preparations completely restored the ejaculatory response, ejaculate size, masturbatory behaviour, and seminal carnitine levels. In conclusion, androgen substitution with dihydrotestosterone-enanthate, in equivalent doses, is as effective as testosterone-enanthate in restoring reproductive functions in hypogonadal monkeys.

Prenatal Development of Gonadotropin-Releasing Hormone Receptors in the Rat Anterior Pituitary*

The development of pituitary GnRH receptors was studied in the rat with in vitro and in vivo autoradiography. GnRH receptors were first seen in pituitary primordia of 13-day-old fetuses. The binding was specific and saturable and was abolished in the presence of 10 microM synthetic GnRH. To examine whether GnRH was available to the fetus, amnionic fluid was collected on days E 12-18. RIA analyses showed that GnRH levels in the amnionic fluid were low on days 12 and 13 (0-20 pM/ml) and rose to 225 pM/ml on day E 16 before they declined to 110 pM/ml on fetal day E 18. The highest levels of GnRH in the amnionic fluid on day E 16 coincided with the first appearance of immunoreactive LH cells, as determined by immunohistochemistry. Intravenous injection of 500 microliters amnionic fluid into pentobarbital-anesthetized adult rats caused a transient 40-60% increase in circulating serum LH in the recipient animal. To show that GnRH from the amnionic fluid has access to the developing pituitary, the 125I-labeled GnRH agonist Buserelin was injected into the amnionic fluid of 13-, 14-, and 15-day-old fetuses in the presence or absence of 10 microM unlabeled GnRH. Autoradiographic analysis of the fetal tissue indicated that the labeled GnRH agonist bound to specific receptors in the primordial pituitaries. The results suggest that the pituitary gonadotropes are differentiated before day E 13 because the expression of GnRH receptors is already an indication of cell determination. Since GnRH is present in the amnionic fluid in a biologically active form and can reach the fetal pituitary, it is concluded that GnRH may be an important factor determining the onset LH synthesis, but not the differentiation, of primordial pituitary cells.

Use of gonadotropin-releasing hormone for hastening ovulation in transitional mares.

Natural GnRH and its analog have potential for hastening ovulation in mares. A study was conducted to evaluate the efficacy of a GnRH agonist given either as an injectable or s.c. implant for induction of ovulation in mares. Forty-five seasonally anestrous mares (March) were assigned to one of three groups (n = 15/group): 1) untreated controls; 2) i.m. injection of the GnRH agonist buserelin at 12-h intervals (40 micrograms/injection for 28 d or until ovulation) and 3) GnRH agonist administered as a s.c. implant (approximately 100 micrograms/24 h for 28 d). Six mares per group were bled on d 0, 7, 14 and 21 after injection or insertion of implant. Samples were taken at -1, -.5 and 0 h and at .5, 1, 1.5, 2, 4, 6 and 8 h after GnRH. Additional daily samples were drawn for 28 d after injection or until ovulation. Samples were assayed for concentration of LH and FSH. Progesterone concentrations were determined in samples collected on d 4, 6 and 10 after ovulation. Number and size of follicles and detection of ovulation were determined by ultrasonography. Number of mares induced to ovulate within 30 d was 0 of 15, 7 of 15 and 9 of 15 for groups 1, 2 and 3, respectively. During treatment, follicle sizes were smaller for mares in group 3 (implant). The LH response to GnRH agonist (area under curve) was similar among groups at d 0 but was greater (P less than .05) for mares in group 3 on d 7 and 14 and groups 2 and 3 on d 21 than for controls. A similar pattern was detected for peak concentrations of LH after GnRH on d 0, 7, 14 and 21. Daily concentrations of LH remained low in untreated control mares compared with GnRH-treated mares throughout the sampling period. Concentrations of LH for mares in group 3 that ovulated were elevated greatly above those for group 2 mares, whereas concentrations of FSH were similar in both treatment groups prior to ovulation.

Controlled release of a GnRH agonist from a polyhydroxybutyric acid implant: reversible suppression of the menstrual cycle in the macaque

The use of polyhydroxybutyric acid as a matrix for delivery of the GnRH agonist buserelin was studied in adult stumptailed macaques with regular menstrual cycles. This material contained 5.0 mg buserelin in a disk of 0.6 cm diameter and 0.15 cm thickness. The effects on pituitary-ovarian function were examined and buserelin release profiles from 30,000 and 150,000 molecular weight polyhydroxybutyric acid matrices were compared. In an attempt to reduce the high initial release rate of buserelin from these disks, and to prolong the effective period of release, implants of 30,000 molecular weight were coated with cyanoacrylate. The implants were removed after 28, 35 or 42 days for the 30,000, the 150,000 and the coated implants, respectively. The urinary excretion profile for the agonist revealed a high initial release of buserelin from these implants followed by a rapid decline. The coated disks released significantly less (p less than 0.05) buserelin over the first 3 days than did either of the uncoated implants, but maintained release of the agonist over a longer period. Inhibition of ovulation and suppression of estradiol secretion lasted for the duration of treatment in 3 of 5 macaques receiving the 30,000 implant, and in 5 of 5 receiving the 150,000 or the coated implant. In 3 macaques in whom the coated implant was left in situ, ovulation was suppressed for 104 +/- 3.7 days. These results demonstrate that a polyhydroxybutyric acid matrix can be used as a depot formulation for a GnRH agonist and that improved control of release of the agonist can be achieved by coating such implants with cyanoacrylate. This approach may be useful in experimental and clinical situations and may be applicable for delivery of other peptide hormones.

Pituitary and ovarian responses of post-partum acyclic beef cows to continuous long-term GnRH and GnRH agonist treatment

Post-partum acyclic beef cows received continuous long-term treatment with GnRH (200 or 400 ng/kg body wt/h) or the GnRH agonist buserelin (5.5 or 11 ng/kg body wt/h) using s.c. osmotic minipumps which were designed to remain active for 28 days. All treatments increased circulating LH concentrations whereas FSH remained unchanged. Ovulation and corpus luteum (CL) formation as judged by progesterone concentrations greater than or equal to 1 ng/ml occurred in 0/5 control, 4/5 200 ng GnRH, 4/4 400 ng GnRH, 4/5 5.5 ng buserelin and 3/5 11 ng buserelin cows. The outstanding features of the progesterone profiles were the synchrony, both within and across groups, in values greater than or equal to 1 ng/ml around Day 6, and the fact that most CL were short-lived (4-6 days). Only 3 cows, one each from the 400 ng GnRH, 5.5 ng buserelin and 11 ng buserelin groups, showed evidence of extended CL function. Cows failed to show a second ovulation which was anticipated around Day 10 and this could have been due to insufficient FSH to stimulate early follicular development, or the absence of an endogenously driven LH surge. The highest LH concentrations for the respective groups were observed on Days 2 and 6 and by Day 10 LH was declining, although concentrations did remain higher than in controls up to Day 20.(ABSTRACT TRUNCATED AT 250 WORDS)

GnRH-agonist therapy in women with the polycystic ovarian syndrome: Effects on ovarian volume and on gonadotropin and sex steroid levels

Eleven patients with infertility and polycystic ovarian syndrome were treated with the GnRH agonist buserelin, 100 micrograms administered intranasally 6 times daily. The ovarian volume and morphology were monitored by vaginal sonography, and serum levels of hormones were measured by immunoassay. The mean ovarian volume was reduced from 13.0 +/- 4.1 cm3 to 9.1 +/- 3.1 cm3 after 42 days of treatment, p less than 0.001. The number of discernible ovarian microcysts was reduced from 11.9 +/- 2.1 to 9.6 +/- 2.9, p less than 0.05. The gonadotropin levels were reduced in all patients; however, there was no direct relationship between the reduction in ovarian volume loss and the concomitant decrease in LH or FSH levels. The levels of testosterone and androstenedione were normalized, whilst estradiol was suppressed to postmenopausal levels during the treatment period. The decrease in ovarian volume and the suppressed levels of ovarian steroids therefore seem to be related to the inhibition of the pituitary-ovarian axis with the GnRH agonist.

The Premenstrual Syndrome: A Study Of Its Diagnosis And Pathogenesis

The premenstrual syndrome (PMS), with its characteristic combination of mental and physical symptoms recurring in the luteal phase of each menstrual cycle and disappearing after the onset of the menstruation, has during recent decades attracted the interest of many researchers. However, the lack of a commonly accepted definition and way to diagnose PMS has led to contradictory results in attempts to establish the etiology of PMS, which still is obscure, and to find ways to treat the complaints.In this study of 82 patients, a diagnostic procedure for PMS was developed, based on prospective daily ratings of symptoms, statistical criteria and non‐parametric statistics. Three subgroups of subjects were identified: group 1, the pure PMS group, with significant symptom cyclicity and all symptoms concentrated to the luteal phase; group 2, the PMS aggravation group, with significant cyclicity but with negative symptoms also appearing prior to ovulation; group 3, the non‐PMS group, i.e. those who do not suffer from menstrually related symptoms.The three subgroups were investigated concerning possible distinguishing demographic factors, and medical and psychiatric anamnesis. The only significant difference found was a lower frequency of pathological scores for neuroticism in the Eysenck Personality Inventory and of a previous psychiatric history in group 1.Among 124 women seeking help for PMS, 8 were found who had one ovulatory and one spontaneously occurring anovulatory cycle. In the ovulatory cycles, a typical symptom cyclicity was evident. In the anovulatory cycles this cyclicity disappeared and the symptoms abated, indicating the importance of a corpus luteum in precipitating PMS.The role of hormonal variations was also studied in 22 postmenopausal women receiving either estradiol only, or estradiol/progestagen sequential therapy. When the progestagen was added to the treatment in the latter group, a PMS‐like syndrome was induced–but not in the “estradiol only” group.To further test the role of ovulation‐anovulation in the pathogenesis of PMS, 26 PMS patients were given the GnRH agonist buserelin in a dose of 400 μg daily intranasally in a double‐blind cross‐over study, versus placebo. Though an appreciable placebo effect was noted, the active drug gave significantly better symptom relief. In the last cycle during medication with active drug 19 of the remaining 23 patients showed a non‐cyclic pattern in their symptoms; thus they no longer had PMS.In each of 18 carefully diagnosed PMS patients the varying effects of hormone concentrations on the severity of symptoms were investigated in two cycles. The results show that in cycles with higher serum concentrations of progesterone–and particularly estradiol–the patients also had more severe symptoms, which contradicts earlier theories of PMS being due to a lack of progesterone.

Acute pituitary-ovarian response during chronic luteinizing hormone-releasing hormone agonist administration in polycystic ovarian syndrome.

The purpose of the study was to evaluate the acute effect of daily subcutaneous injections of the GnRH agonist Buserelin on serum concentration of LH (evaluated by radioimmunoassay (iLH), and by bioassay (bioLH], FSH, oestradiol and testosterone in 20 women with a diagnosis of polycystic ovarian disease (PCO). Buserelin was administered subcutaneously at the dose of 200 micrograms three times daily for 7 days followed by 500 micrograms once daily for a total treatment period of 6 months. Blood samples were drawn immediately before and 2, 4 and 6 h after the injection on the first day of treatment as well as after 1, 2, 3, 4, 12 and 24 weeks. The first injection of Buserelin induced statistically significant rises of iLH, bioLH and FSH as well as of 17 beta-oestradiol. The acute response of gonadotrophins was suppressed after 1 week but a partial recuperation of FSH and iLH responses was observed starting after 2 and 4 weeks of treatment. No significant acute changes of bioLH or of 17 beta-oestradiol and testosterone could be seen. The persistence of a small but statistically significant pituitary response in the first hours following the daily injection of the peptide suggests a hyper-reactive state of the gonadotrophs in PCO patients. Such acute pituitary responses are not seen when a similar treatment is administered to endocrinologically normal women. This observation could be an argument in favour of an initial central defect in the pathogenesis of the syndrome.

Doppler assessment of uterine blood flow changes in patients with fibroids receiving the gonadotropin-releasing hormone agonist Buserelin

Uterine arterial blood FVWs were studied by doppler ultrasound in eight patients with large uterine fibroids who were treated with the GnRH agonist Buserelin intranasally for 4 months. At the end of treatment, reductions in the uterine and discrete fibroid volumes were associated with significant increases in the mean RI values for the uterine (P less than 0.01) and fibroid (P less than 0.001) vasculature, thus indicating reduction in blood flow.

An implant of a gonadotropin releasing hormone agonist (buserelin) which suppresses ovarian function in the macaque for 3-5 months.

Four adult female stumptailed macaque monkeys with regular menstrual cycles and one with irregular cycles and dysfunctional uterine bleeding were treated with a single implant containing 2.6 mg of the GnRH agonist buserelin in a matrix of polylactide/glycolide copolymer (75:25). The implant was used as a cylindrical rod of 0.8 X 0.12 cm and implanted sc in the abdominal wall. The insertion of the implant was followed by a modest rise in serum concentrations of LH and FSH lasting 3-4 days before falling to basal values. The release profile of buserelin from the implant was measured in urine by a radioimmunoassay detecting the intact molecule and its major metabolites. Immunoreactive buserelin in urine was high between days 1-3 after implant after which there was a rapid decline to form a plateau between days 15-70 followed by a further gradual decline. This prolonged release of buserelin suppressed ovulation for a mean of 148 days (range 105-182 days) as indicated by absence of serum progesterone rises. Serum FSH concentrations were low for at least 75 days and during this time serum oestradiol concentrations were uniformly suppressed in all monkeys. Once the buserelin release from the implant declined serum FSH concentrations began to rise. There was a variable delay of 7-60 days before this rise in FSH was associated with stimulation of ovarian oestradiol secretion followed by rises in serum progesterone concentrations indicative of ovulation. Apart from the first menses after insertion of implant, 4 of the monkeys became amenorrhoeic for the period of anovulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth, bone maturation, pituitary-gonadal function and adrenarche during treatment of central precocious puberty (CPP) with the GnRH agonist buserelin (Bn)

Growth, bone maturation, pituitary-gonadal function and adrenarche during treatment of central precocious puberty (CPP) with the GnRH agonist buserelin (Bn)

Growth and adrenarche during treatment of central precocious puberty (CPP) with the GnRH agonist buserelin (B)

Growth and adrenarche during treatment of central precocious puberty (CPP) with the GnRH agonist buserelin (B)

Treatment (RX) of precocious puberty with the synthetic GnRH agonist buserelin (HOE 766)

Treatment (RX) of precocious puberty with the synthetic GnRH agonist buserelin (HOE 766)

Reversible induction of azoospermia in rhesus monkeys by constant infusion of a gonadotropin-releasing hormone agonist using osmotic minipumps.

This study documents the long term, reversible, antireproductive effects of GnRH agonist treatment in adult male rhesus monkeys. Constant sc infusion of the GnRH agonist buserelin by osmotic minipumps over 20 weeks resulted in an initial rise in serum LH, followed by a decline to undetectable levels, indicating pituitary desensitization. This rise and fall of plasma LH was paralleled by serum testosterone concentrations. The RHLH response to an iv bolus injection of GnRH was completely abolished, and the corresponding Leydig cell response was also lost. Testicular volumes decreased markedly, and spermatogenesis was inhibited to azoospermic levels. Spontaneous and electrostimulated ejaculatory activities were lost under prolonged buserelin infusion. The animals were then supplemented with exogenous testosterone to reestablish ejaculatory behavior which had been curtailed under low circulating androgen levels, and azoospermia persisted. Such pronounced effects could not be demonstrated in our previous studies using daily or twice daily injections with higher agonist doses. When treatment was stopped after 20 weeks, the inhibitory effects of the GnRH agonist were reversible, and full pituitary and gonadal functions were recovered. It is concluded that constant infusion of GnRH agonist is far more effective in male rhesus monkeys than daily injections and that the suppressive effects of GnRH agonist application are fully reversible. Thus, a suitable primate model for further research on a GnRH agonist-based male contraceptive has been established.