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Lupron,
Antagon, and Cetrotide are fertility drugs that "down regulate" reproductive hormone
production causing a reduction in levels of follicle
stimulating hormone, luteinizing hormone, and estrogen.
Lupron, Antagon, and Cetrotide all cause these effects,
however, by different physiologic mechanisms.
Lupron
is widely used for the treatment of endometriosis and was the first "down regulator" used in
in vitro fertilization cycles. Endometrial cells are
dependent upon estrogen for growth and Lupron dramatically
lowers estrogen levels. Unfortunately, this lowering
is accompanied by the same side effects as menopause.
Lupron,
Antagon and Cetrotide are administered according to
specific protocols in IVF to
prevent premature ovulation, and in some cases to exacerbate
the response to follicle stimulating hormone (flare
protocol).
Lupron
is a GnRH agonist which works at the hypothalamus (a
small gland located at the base of the brain ) whereas
Antagon is a GnRH antagonist which completely blocks
the effect of gonadotropin releasing hormone at the
pituitary gland thus creating a "more complete
"down regulation".
IVF
cycles are precisely timed to insure that the follicles
are optimally developed at the time of retrieval. FSH
is administered and dosages are adjusted based upon
periodic ultrasound scans and estradiol measurements.
In a "normal" or "non-stimulated"
cycle, luteinizing hormone surges to signal ovulation.
If this occurs too soon in an IVF
cycle, ovulation could be triggered before the eggs
are mature and the cycle could be lost. The LH surge
cannot occur while Lupron, Antagon, or Cetrotide are
administered thus premature ovulation is prevented.
Once
the follicles are mature, an injection of hCG is given
36-38 hours prior to retrieval to signal ovulation.
The body responds to hCG in the same manner as it does
to LH.
Many infertility
clinics choose to use Antagon or Cetrotide because
the down regulation is more complete and the dosing
regimen is easier. Lupron is started 7 days before the
next expected menses and Antagon or Cetrotide is started
after 4 to 6 days of FSH stimulation. Doses vary dependent
upon patient specific protocols.
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