The percent drop. (Garnick 1999, cited in Cook


The use of GnRH analogues is common in hormone dependent
cancers. The prostate gland of males located under the bladder and in front of
the rectum, is the most common place for cancer amongst men. (Attard
et al., 2015) This can cause pain when urinating, blood in urine and pelvic pain. Known
risks are to be age, race and family history. Prostate growth, maintenance and
activity requires the presence of androgens. Unlike other reproductive organs
the prostate continues to grow with the help of androgens, this can allow for
the manifestation of oncogenic cells. Prostate- specific antigen (PSA)
screening, ultrasound, MRI and an enlarged prostate during rectal examinations
conducted by a physician are main ways of detecting the cancer; a prostate
biopsy is done to confirm the diagnosis. (Cook, 2000)

             Treatment for the cancer depends on how
violent the cancer is, if deemed appropriate a consultant may prescribe a GnRH
analogue. An antagonist blocks the receptor and immediately prevents LH
release, therefore preventing the stimulation of androgen synthesis. (Cook,
2000) Agonists can be used, however due to the following flare effect it can
cause a temporary worsening of the cancer.

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            A study of
36 prostate cancer patients whom were treated with Abarelix, a GnRH antagonist, was conducted. Results from the study
presented a median of 35 percent decrease in prostate volume, alongside the
depression of testosterone and PSA values. Furthermore, once treatment had
stopped testosterone levels returned to normal while PSA levels remained low. (Garnick
1999, cited in Cook 2000) Phase two of the study included 300 patients, 209
treated with a abarelix and the remaining 33 treated with an agonist. The
results presented on the eighth day the antagonist group had a 76 percent drop
in testosterone whereas the agonist group had a zero percent drop. (Garnick
1999, cited in Cook 2000) Understanding the functioning of agonists, the lack
of hormonal change is most likely due to the flare effect. Within the study, a
control group of untreated patients should have been presented to showcase observe
any affects the agonist group may have had. Since agonists have been a primary
treatment for hormone related cancers, with the discovery of antagonists it
removes the need for anti-androgens which present their own adverse effects. Additionally,
due to the discovery of antagonists being recent the long-term side effects of
these drugs are still unknown.



For the ability of the reproductive
system to carry out unimpaired function is determined on the accurate performance
of the HPG axis and the hormones involved.  Discovery of GnRH and the gonadotrophins, FSH
and LH, furthered the understanding scientists had of the HPG axis. Following
the breakdown of the GnRH amino acid sequence allowed for the creation of interventions
for reproductive pathology such as agonists and antagonists to aid in treatment.

 These GnRH analogues prevent the
secretion of FSH and LH which results in a decrease in gonadal hormones which
aid in controlling and maintaining ongoing reproductive disorders. Studies
conducted on analogues presented good results, agonists delivered to precocious
puberty patients at an early age yielded the best patient response to the
treatment. Antagonists present as suitable treatment options for hormone
related pathology due to the fact that it lacks the flare effect and therefore
eliminates the need for anti-androgens.  Ongoing
research may open new areas of understanding of the analogues used in clinical practice
and aid in relieving negative side effects the drugs may cause.