Transcript Slide 1

GnRH
What triggers human puberty is one of the
central mysteries of reproductive biology.
What factors are responsible for the
amplification of the pulsatile gonadotrophinreleasing hormone (GnRH) signal intrinsic to
GnRH neurones (1) at the expected time of
sexual maturation?
What factors modulate the amplitude and
frequency of GnRH throughout reproductive life,
particularly during the female menstrual cycle?
GnRH
L’ormone che induce il rilascio delle
gonadotropine (GnRH) è il principale
regolatore della cascata ormonale coivolta
nella riproduzione ed è stato isolato
dall’area preottica dell’ ipotalamo di
mammiferi. E’ un decapeptide ed è
rilasciato nel circolo sanguigno a livello
della eminenza mediana in modo pulsatile
di quantità precise dagli assoni di neuroni i
cui terminali sono localizzati nell’ipofisi
anteriore. Il rilascio di questo ormone
avviene ogni 30-120 minuti il quale regola
la biosintesi e la liberazione di LH e FSH
dall’ipofisi anteriore. La frequenza di
rilascio del GnRH è massima durante
l’ovulazione mentre è ridotta al minimo
durante la fase luteale. La secrezione di
GnRH e’ controllata negativamente da
steroidi gonadici mentre neurotrasmettitori
ad azione inibitoria quali il GABA,
aminoacidi eccitatori (acido glutammico),
peptidi oppioidi endogeni, monoamine del
sistema noradrenergico, dopaminergico e
serotoninergico, acetilcolina, melatonina,
ossitocina modulano il rilascio di GnRH.
Struttura GnRH negli animali
GnRH deficiency
The syndrome characterised by endogenous GnRH
deficiency, i.e. normosmic idiopathic
hypogonadotrophic hypogonadism (nIHH) is
characterised by abnormal/absent GnRHinduced
luteinising hormone (LH) pulsations in which patients
present with delayed or absent pubertal development
and other associated somatic abnormalities.
Although rare, nIHH is a disease caused by defects
in the synthesis, secretion and action of GnRH and,
therefore, has long been considered an important
entrée to understanding the modulators of GnRH in
humans.
Sequenza di eventi causati
dal GnRH:
1) Induce secrezione di FSH
ed LH che a loro volta
stimolano l’accrescimento
di follicoli ovarici e la
produzione di testosterone
o estradiolo
Kisspeptin released by neurons in the AVPV and Arc stimulates GnRH release,
which induces the release of LH and FSH.
REVIEW
ARTICLE
published:
09 April 2012
Estrogen has a bimodal effect on the hypothalamus with both an inhibitory and
stimulatory influence on GnRH secretion.
The stimulatory effect of estrogen is seen at the end of the follicular phase
where estrogen triggers the preovulatory GnRH surge.
The inhibitory effect of estrogen on GnRH secretion and GnRH gene
expression has been shown in in vivo studies in several mammalian species.
Studies in ewes indicate that estrogen inhibits GnRH pulse amplitude in the
early follicular and luteal phase of the cycle.
The more prevalent hypothesis is that the influence of estrogen on GnRH is
not direct but is conveyed to GnRH neurons via presynaptic afferents from
adjacent cells that express ER (now thought to be kiss1 neurons).
Kisspeptin
Kisspeptin peptides are the most powerful stimulators of
gonadotrophin secretion that have ever been studied in
mammalian species, including rodents on a molar basis (19–
24), sheep (25) and monkeys (26). Intracerebral doses as low
as 1 fmol evoke significant LH responses (20). The effects of
kisspeptin on LH can be completely abrogated by the coadministration of a GnRH antagonist, demonstrating that this
protein is acting through the GnRH receptor to stimulate LH
release (i.e. hypothalamic effect) (20). Kisspeptin is unable to
stimulate LH release when given to GPR54 knockout mice,
suggesting that the stimulatory effects of this peptide are
mediated only through its cognate receptor
Kisspeptins and KISS1R
Discovery and nomenclature
Kisspeptins comprise a family of peptides derived from the primary translation
product of the KISS1 gene, localized to chromosome 1, which were identified
more than a decade ago (Lee et al. 1996). These peptides were discovered as the
result of a systematic bioinformatics search for processed peptides encoded
by the human genome (Ohtaki et al. 2001), and simultaneously by the isolation of a
biological activity from human placenta and its identification by mass
spectrometry (Kotani et al. 2001). Proteolytic processing of the full-length 145 amino
acid kisspeptin protein results in shorter fragments of the carboxyl
(C)-terminus region of the molecule with 54 (KP-54; previously designated metastin),
14 (KP14), 13 (KP-13) or 10 (KP-10) amino acids (Kotani et al. 2001, Ohtaki et al.
2001). Initially, the largest cleavage product, KP-54 was identified for its ability to
suppress the metastatic potential of malignant melanoma cells
(Lee et al. 1996, Lee & Welch 1997) and it was therefore termed ‘metastin’ (Ohtaki et
al. 2001). Interestingly, the naming of the gene KISS1 and its product,
kisspeptin (aka metastin), was made by the team of scientists who discovered
the gene in the town of Hershey, Pennsylvania, famous for its chocolate
‘kisses’, with inclusion of the terminology ‘SS’ also indicating a suppressor
sequence. The term ‘kisspeptins’is now widely employed to collectively describe this
family of peptides that show an Arg–Phe–NH2 motif at the C-terminus, characteristic
of the extensive RF-amide peptide superfamily (Roa et al. 2008).
GnIH possesses the RFamide (Arg-Phe-NH2) motif at its C-terminus and thus
belongs to the RFamide peptide family. The first identified RFamide peptide, PheMet-Arg-Phe-NH2 (FMRFamide), was a cardioexcitatory molecule isolated from the
ganglia of the venus clam Macrocallista nimbosa (35). In 2000, an RFamide peptide
was isolated from the brain of the Japanese quail using high-performance liquid
chromatography (HPLC) and a competitive enzyme-linked immunosorbent assay
for the dipeptide Arg-Phe-NH2 (8). The isolated peptide was a previouslyunreported dodecapeptide (SIKPSAYLPLRFamide).
The cDNAs of human, monkey and cow (bovine) also encoded three GnIH
orthologs, which were termed RFRP-1, -2 and -3 (62). However, in contrast to other
vertebrates, RFRP-2 is not predicted to be an RFamide peptide, although this
mature peptide has not yet been isolated so it is unknown if it is actually cleaved
from the precursor.
The HeLa cell line
was derived from
cervical cancer
cells of
Henrietta Lacks,
a patient who died
of her cancer on
October 4, 1951.
Arr = Arrestina
extracellular-signal-regulated kinases (ERKs)
Low levels of GnRH release during the wake period in
early puberty are thought to be dependent on negative
feedback from progesterone (P4), consistent with a sharp
rise in circulating P4 levels in the morning.
P4 inhibition of GnRH neuronal activity occurred when
both excitatory inputs were blocked, supporting the
hypothesis that P4 can act directly on GnRH neurons.
Ruolo degli aminoacidi nella sequenza del GnRH
GnRH agonisti
GnRH antagonisti
GnRH analogs
pharmacological
physiological
GnRH agonist
FSH
& LH
Pulsatile GnRH
GnRH
GnRH antagonist
FSH
& LH
FSH LH
FSH
& LH
It took a considerable period of time after the
elucidation of GnRH to generate clinically useful
antagonists (GnRH ant). The third generation
compounds (Ganirelix (Organon, Cambridge, UK)
and Cetrorelix (Merck-Serono, Feltham,UK))
reached the market in 2001.Their ability to induce
immediate suppression and subsequent rapid
recovery of pituitary function is particularly
appropriate to their short term use in IVF.
There are, however, differences between the GnRHa induced LH surge and the LH surge
of the natural cycle; the LH surge of the natural cycle being characterized by three phases
with a total duration of 48 h (Hoff et al., 1983) as compared with the GnRHa induced LH
surge consisting of two phases with a duration of 24–36 h (Itskovitz et al., 1991). This
leads to a significantly reduced total amount of gonadotrophins (LH and FSH) released
from the pituitary when GnRHa is used to trigger final oocyte maturation (Gonen et al.,
1990; Itskovitz et al., 1991) resulting in corpus luteum deficiency and a defective luteal
phase (Segal and Casper, 1992; Balasch et al., 1995).
DEGARELIX
Degarelix is a synthetically modified analogue of azaline B with GnRH
antagonist activity. It was approved by the US FDA in December 2008
for the management of advanced prostate cancer.
“Early studies in the structure–activity relationships of GnRH
peptides identified His2 as critical for receptor activation.”
Applicazioni cliniche dei GnRH agonisti e antagonisti
Curr Opin Obstet Gynecol. 2010 Aug;22(4):283-8.
Gonadotropin-releasing hormone agonist and add-back therapy: what do the
data show?
Surrey ES.
Colorado Center for Reproductive Medicine, Lone Tree, Colorado, USA.
Abstract
PURPOSE OF REVIEW: Endometriosis is a gynecologic disorder that can lead
to debilitating chronic pelvic pain and infertility. Gonadotropin-releasing
hormone agonists (GnRHa) have emerged as a primary medical therapy for
patients with symptomatic disease, but secondary hypoestrogenic side
effects may limit compliance. Add-back therapy is a means of surmounting this
problem.
RECENT FINDINGS: Progestins such as norethindrone acetate may be administered with or
without addition of low doses of estrogens to safely and effectively extend GnRHa therapy
while minimizing side effects. Recent studies have demonstrated that the use of add-back
enhances compliance and duration of therapy. The initiation of an add-back should not be
deferred given evidence demonstrating an increase in vasomotor symptoms and bone loss if
not administered concomitantly. The subset of adolescents with endometriosis who require
GnRHa therapy should be administered an add-back, but require careful monitoring of bone
mineral density.
SUMMARY: Implementation of an appropriately selected add-back will significantly
reduce hypoestrogenic side effects, enhance compliance, and allow for
prolongation of therapy without interfering with the efficacy of GnRHa in treating
symptomatic endometriosis.
Background Systematic reviews have found that luteinizing hormone – releasing hormone (LHRH) agonists are effectivein treating
premenopausal women with early breast cancer.
Methods We conducted long-term follow-up (median 12 years) of 2706 women in the Zoladex In premenopausal Patients (ZIPP),
which evaluated the LHRH agonist goserelin (3.6 mg injection every 4 weeks) and tamoxifen (20 or 40 mg daily), given for 2 years.
Women were randomly assigned to receive each therapy alone,
both, or neither, after primary therapy (surgery with or without radiotherapy/chemotherapy). Hazard ratios
and absolute risk differences were used to assess the effect of goserelin treatment on event-free survival
(breast cancer recurrence, new tumor or death), overall survival, risk of recurrence of breast cancer, and
risk of dying from breast cancer, in the presence or absence of tamoxifen.
Results Fifteen years after the initiation of treatment, for every 100 women not given tamoxifen, there were 13.9 (95% confidence
interval [CI] = 17.5 to 19.4) fewer events among those who were treated with goserelin
compared with those who were not treated with goserelin. However, among women who did take tamoxifen,
there were 2.8 fewer events (95% CI = 7.7 fewer to 2.0 more) per 100 women treated with goserelin
compared with those not treated with goserelin. The risk of dying from breast cancer was also reduced at
15 years: For every 100 women given goserelin, the number of breast cancer deaths was lower by 2.6
(95% CI = 6.6 fewer to 2.1 more) and 8.5 (95% CI = 2.2 to 13.7) in those who did and did not take tamoxifen,
respectively, although in the former group the difference was not statistically significant.
Conclusions Two years of goserelin treatment was as effective as 2 years of tamoxifen treatment 15 years after starting therapy. In
women who did not take tamoxifen, there was a large benefit of goserelin treatment on survival and recurrence, and in women who
did take tamoxifen, there was a marginal potential benefit on
these outcomes when goserelin was added.
Background: The usefulness of long-term, low-dose gonadotropin-releasing hormone agonist (GnRHa; buserelin acetate)
therapy, so-called draw-back therapy, for the treatment of adenomyosis was investigated .
Material/Methods: A retrospective observational study was conducted covering the period between January 2003 and
March 2008. The subjects consisted of 12 patients with adenomyosis who underwent draw-back therapy
for 2 years and had previously received GnRHa. GnRHa was initiated at 900 μg/day (6 nasal
sprays/day). When the CA-125 level normalized, the GnRHa dosage was adjusted to 150–750 μg/day
to achieve a plasma estradiol (E2) concentration of 20–50 pg/ml (i.e., the therapeutic window).
Pain during withdrawal bleeding and chronic pelvic pain were assessed using a visual analogue
scale. In addition, bone mineral density (BMD) of the lumbar vertebrae was measured using dualenergy
X-ray absorptiometry.
Results: The mean GnRHa dose during draw-back therapy was 435 μg/day (2.9 nasal sprays/day). The mean
E2 level during draw-back therapy was 36.3±14.3 pg/ml. The intensity of chronic pelvic pain was
signifi cantly lower during draw-back therapy than before draw-back therapy, and was nearly eliminated
in many patients (4.8±1.2 vs. 0.6±0.7, respectively [p=0.000]). Compared to the severity of
vasomotor symptoms during previous regular GnRHa therapy, the severity of vasomotor symptoms
during draw-back therapy was signifi cantly lower (3.8±0.7 vs 1.1±0.7, respectively [p=0.000]). The
decrease in BMD during a 6-month course of treatment was 0.96±0.9%.
Conclusions: GnRHa draw-back therapy allowed maintenance of plasma E2 levels within the therapeutic window.
GnRHa can thus be administered for long periods of time while maintaining therapeutic effects
on adenomyosis and suppressing adverse events.
In this study, we aim to evaluate the clinical outcome and patient’s convenience of
single administration of long-acting GnRHa (goserelin depot) as compared
with multiple daily administrations of short-acting GnRHa (buserelin or
leuprorelin).
With its extreme molecular weights, hCG is the longest circulating
molecule in human blood with a circulating half life of 36 hours. Secondly, as
described in this review, there are amazingly 5 unique variants of hCG, each
having identical amino acid sequence, produced by different cells and having
independent functions. These are hCG, sulfated hCG, hyperglycosylated hCG,
hCG free ß-subunit and hyperglycosylated hCG free ß-subunit. There is
no other molecule like hCG.
A major function of hCG during pregnancy can be described as driving
hemochorial placentation, or the efficient method whereby humans drive nutrient
transfer to the fetus.
The alfa-subunit of hCG comprises 92 amino acids and 2 N-linked (Asn-linked)
oligosaccharides [46]. The ß-subunit comprises 145 amino acids, 2 N-linked (Asnlinked) and 4 O-linked (Ser-linked) oligosaccharides [46].
hCGs in pharmacological preparations were
originally derived from urinary samples of
pregnant women. Urinary hCG (uhCG) products
may have, however, great biological variability
with a significant batch-to-batch variation due to
their human origin. Therefore, recombinant
technology has been introduced for the
production of recombinant hCG (rhCG) with
high-purity and batch-to-batch consistency.
Other advantage of rhCG products over uhCG
preparation is their availability in different dose
strengths that provide an opportunity for
individualized therapy.
Human chorionic gonadotrophin (hCG) has been the gold standard for
ovulation induction as a surrogate for the mid-cycle LH surge for several
decades. Due to structural and biological similarities, hCG and LH bind to
and activate the same receptor, the LH/hCG receptor (Kessler et al., 1979).
An important difference, however, exists between the half-life of LH
and hCG, as the half-life of LH is 60 min (Yen et al., 1968) whereas
that of hCG is >24 h (Damewood et al., 1989). Due to its prolonged
circulatory half-life, hCG exerts a sustained luteotropic activity, and
may induce the occurrence of ovarian hyperstimulation syndrome
(OHSS) (Delvigne and Rozenberg, 2002). When GnRH antagonist
protocols were introduced for the prevention of a premature LH surge
(Albano et al., 1997; Itskovitz-Eldor et al., 1998; Borm and Mannaerts,
2000) it became possible to trigger final oocyte maturation and ovulation
with a single bolus of a GnRH agonist (GnRHa) as an alternative to hCG
(Nakano et al., 1973).
In both rodents (4) and humans (10), AMH expression starts
in the columnar granulosa cells of primary follicles, is highest
in granulosa cells of preantral and small antral follicles, and
gradually diminishes in the subsequent stages of follicle
development so that AMH is no longer expressed during the
gonadotropin-dependent terminal stages of follicle
development. In addition, AMH expression disappears when
follicles become atretic.