Long-term GnRH-agonist administration revealed a GnRH-independent mechanism stimulating FSH discharge in humans

Synthetic luteinizing hormone releasing hormone (LHRH) vaccine for effective androgen deprivation and its application to prostate cancer immunotherapy

We have designed a peptide-based immunotherapeutic vaccine for treatment of androgen-responsive prostate cancer. The vaccine targets the luteinizing hormone-releasing hormone (LHRH) decapeptide that results in an androgen-deprivation immunotherapy. The design elements of the peptide immunogens are the LHRH peptide or B cell epitope synthetically linked to different promiscuous helper T cell (Th) sequences, the UBITh epitopes, derived from four natural pathogens for effective immunogenicity in outbred populations, and in some cases, also linked to an adjuvanting peptide from Yersinia invasin (Inv) protein. The UBITh LHRH immunogens are adsorbed on Alhydrogel or formulated as several different oil-based emulsions and tested in rodents, dogs, and a non-human primate, baboons. The immunogens generate an anti-LHRH antibody response specific to the LHRH decapeptide element in contrast to LHRH conjugate-carrier protein vaccines where only a small portion of the antibody response is directed to the target epitope and epitopic suppression is noted. Individual UBITh peptide domains, but not the LHRH and Inv peptide domains, are stimulatory in lymphocyte cultures. The UBITh LHRH immunogens in a clinically applicable formulation, controlled the growth of Dunning R3327-H androgen-responsive prostate tumor cells in rats. The results demonstrate universal responsiveness and long duration of androgen deprivation from three diverse species, and thus vaccine efficacy.

Pivagabine decreases stress-related hormone secretion in women with hypothalamic amenorrhea

Stress-induced neuroendocrine activities influence the regulation of endocrine glands and axes. Weight loss-related hypothalamic amenorrhea is a typical stress-induced physiopathological condition. It is characterized by increased adrenal cortex activation and by reduced GH, LH, FSH and gonadal steroid hormone levels. The aim of the present study was to investigate the effects of pivagabine, a neurotropic drug (1800 mg/day for 7 days) or placebo administration on ACTH, cortisol, GH, LH, FSH and PRL plasma levels in patients with hypothalamic amenorrhea related to weight loss. Hormonal parameters and the pulsatile release of cortisol (6-hour pulsatility, sampling every 10 minutes) were evaluated before and after 7 days of treatment. Pivagabine administration significantly reduced mean plasma ACTH (from 21.7+/-1.7 to 15.4+/-1.2 pg/ml, p<0.05) and cortisol levels (from 12.2+/-0.7 to 9.7+/-0.7 ng/ml, p<0.05) and increased GH levels (from 1.4+/-0.5 to 3.0+/-0.9 ng/ml, p<0.05). A significant reduction of cortisol pulse amplitude was observed (p<0.01) while no change in pulse frequency occurred. No changes were observed in placebo-treated subjects. LH, FSH and PRL levels were not modified by placebo or pivagabine administration. In conclusion, in patients with hypothalamic amenorrhea related to weight loss pivagabine induced a significant decrease of cortisol secretion and an increase of GH release by pivagabine administration, suggesting that this drug exerts a specific neuroendocrine modulatory role.

Pharmacokinetics and pharmacodynamics of GnRH agonists: clinical implications in pediatrics

Since 1981, GnRH agonist administration has been the treatment of choice for central precocious puberty. Continuous administration of the agonist, instead of permanently stimulating gonadotropin secretion, deeply suppresses LH and FSH levels and induces a marked inhibition of gonadal activity and regression of clinical symptoms. This inhibitory effect is due both to specific kinetic parameters relative to natural GnRH, and to marked alterations of the biosynthetic pathways of gonadotropin subunits. The half disappearance time of infused agonists is 3-10 fold that of natural GnRH. This means that the residence time of GnRH agonists is significantly longer than that of GnRH. The resistance of agonist to enzymatic degradation, mainly due to the substitution of a hydrophobic D-amino acid for glycine 6, is one of the factors involved in the increased availability of GnRH superagonists. The paradoxical effects of GnRH superagonists are still incompletely understood. In children long-term treated with depot formulations of triptorelin or leuprorelin, alpha-subunit secretion is markedly increased, and remains sensitive to exogenous GnRH, which demonstrates that the gonadotrophs are not totally desensitized. Despite the sustained stimulation of a-subunit secretion, no deleterious side effects, either during therapy or during post-therapy follow-up, have been reported in children treated with GnRH agonists. It should be noted that alpha-subunit responsiveness to exogenous GnRH decreases progressively after several years of treatment, although it is never completely abolished. On the other hand, LH beta-subunit secretion is suppressed as evidenced by radioimmunoassay of LH beta-subunit in serum chromatographic fractions from children treated with triptorelin. This differential pattern of secretion parallels that of mRNA levels in rat pituitary after in vivo exposure to triptorelin. Both pharmacodynamic and pharmacokinetic data can help diagnose the situations of resistance or escape. The lack of clinical effect of GnRH in the treatment of precocious puberty can be due to true resistance, or to an inappropriate injection schedule, or to abnormal metabolism. Measurement of serum alpha-subunit level, and, if needed, of serum agonist level, generally provides the answer.

The use of a combined regimen of GnRH agonist plus a low-dose oral contraceptive improves the spontaneous pulsatile LH secretory characteristics in patients with polycycstic ovary disease after discontinuation of treatment

PURPOSE

The fertility rate in women with polycystic ovary disease (PCOD) is influenced by the type of treatment received. The present study evaluated the possible correlation between treatment and pulsatile release of gonadotropins.

METHODS

Spontaneous episodic secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and hormonal parameters were monitored before and after 1, 3, and 6 months after treatments suspension. Twenty-four PCOD patients were randomly divided into two groups of 12 subjects. Group A was treated with gonadotropin-releasing hormone (GnRH)-analogue plus oral contraceptive (OC). Group B was treated only with OC. Both groups were treated for 6 months and followed up for 6 months.

RESULTS

In all subjects the therapeutic regimens reduced the androgenic milieau and the gonadotropin plasma levels. Spontaneous pulsatile secretion of LH and FSH was significantly modified in both groups, but patients who received the combined regimen showed a significantly greater reduction of LH plasma levels and a significantly greater decrease of LH pulse amplitude throughout the 6 months after treatment suspension. Ferriman-Gallway score and ovarian volumes were significantly reduced in patients who received the combined treatment than in the OC-treated patients.

CONCLUSIONS

These data support the evidence of a higher efficacy of the combination of GnRH-a + OC than OC alone in restoring a normal and adequate spontaneous episodic gonadotropin discharge and in decreasing Ferriman-Gallway score and ovarian volumes in patients with PCOD.

The transition from pubertal development to postmenopause discloses a gonadotropin-releasing hormone-independent mechanism regulating follicle-stimulating hormone release

The reproductive function is tightly dependent on gonadotropin secretion and the optimal activity of the hypothalamus-pituitary axis. This study discusses evidence that supports the possible existence of a GnRH-independent modulator of FSH secretion in humans. Such a hypothesis has been consistently reported in several experimental animals. To test the hypothesis specific times during the physiological development and activity of the hypothalamus-pituitary axis have been evaluated under the use of drugs acting directly on hypothalamic GnRH-secreting neurons, such as GnRH agonists. The possible presence also in humans of such an independent FSH stimulator might be important for the understanding of anovulation and infertility.

A long-term treatment with gonadotropin-releasing hormone agonist plus a low-dose oral contraceptive improves the recovery of the ovulatory function in patients with polycystic ovary syndrome

OBJECTIVE

To evaluate the hormonal and clinical follow-up after the suspension of a longterm therapy with GnRH-agonist (GnRH-a) plus oral contraceptive (OC) in comparison to OC alone in patients with polycystic ovary syndrome (PCOS).

DESIGN

Hormonal (plasma LH, FSH, sex steroid levels) and clinical (Ferriman-Gallwey score and ultrasound) parameters were monitored at various moments during the 6 months of treatment and during the 6 months after treatment suspension.

SETTING

Physiopathology of Human Reproduction, University of Modena, Italy.

PATIENT(S)

Thirty patients with PCOS were enrolled and randomly subdivided in two groups of 15 each.

INTERVENTION(S)

Group A was treated with 3.75 mg IM GnRH-a plus OC. Group B was treated only with OC.

RESULT(S)

Both therapeutical regimens were effective in reducing androgenic milieu, Ferriman-Gallwey score, and ovarian volume within the 6th month of treatment. However, only patients treated with GnRH-a + OC showed a normal LH:FSH ratio, adequate plasma E2 and P levels, and ovulatory cycles during the 6 months of the after treatment follow-up. Patients treated with OC alone showed no beneficial effect after the 3rd month of the follow-up.

CONCLUSION(S)

These data support the evidence of a higher efficacy of the combined regimen (GnRH-a + OC) than OC alone in the treatment of patients with PCOS. In addition, the former regimen is associated with recovery of normal ovulatory cycles.

Difference of LH and FSH secretory characteristics and degree of concordance between postmenopausal and aging women

OBJECTIVE

Several neuroendocrine changes occur at menopause and the present study aimed to verify whether the episodic release and the degree of concordance of LH and FSH differs between early and late postmenopausal women.

METHODS

Postmenopausal (n = 32) women were enrolled and subdivided in two groups according to the menopausal age: group A (n = 22), patients with more than 2 but less than 5 years from the occurrence of menopause; group B (n = 10), patients with more than 15 years from the occurrence of menopause. All subjects underwent a pulsatility study (4 h, sampling every 10 min) to assess LH and FSH secretory characteristics and their degree of concordance.

RESULTS

Mean +/- S.E.M. LH and FSH plasma levels were lower in older women than in postmenopausal women (P < 0.01). The secretory pattern was pulsatile for both LH and FSH and their pulse amplitudes were lower in aged women (P < 0.01). No significant difference was observed in terms of pulse frequency between the two groups. LH and FSH pulses were co-secreted in early postmenopausal women while such a concordance was lost in older women.

CONCLUSIONS

Late postmenopause is characterized by the reduction of the amplitude of gonadotropin pulses in comparison to women in early postmenopause, reflecting changes of both GnRH secretion and/or pituitary responsiveness to GnRH. The age-related loss of concordance between LH and FSH pulses discloses the existence of a hidden FSH stimulating system, which drives FSH episodic release independently and more promptly than GnRH.