Fertility Medications
Fertility drugs are available to treat many of the conditions that
cause infertility. Many of these fertility drugs,
such as Clomid and FSH, are known as "ovulation
inducing agents." A normal menstrual cycle involves
follicular (egg) recruitment and growth, development of the endometrium,ovulation,
fertilization, and implantation in the endometrium.
These processes are regulated by hormone relationships
in the
"hypothalamic-ovarain-pituitary axis (HPO)." Conditions that adversely affect
the HPO axis can lead to anovulation (lack of ovulation) and infertility. Many
fertility tests are available to help determine the cause of failed ovulation.
Fertility
Drugs and Ovulation
Many fertility drugs work
at the hypothalamus or pituitary gland to influence
the production of FSH, LH, and other hormones.
It is necessary to have a basic understanding
of how the HPO axis functions in order to understand
how these fertility drugs exert their actions.
The
hypothalamus can be compared to a "thermostat"
because it monitors the levels of hormones such
as follicle stimulating hormone (FSH), luteinizing hormone (LH), estrogen,
and others. As it monitors these hormones, it "balances" their levels.
Fertility drugs such as Lupron and Ganirelix exert their
effects by influencing the production of GnRH.
During the first days of the menstrual cycle,
the hypothalamus produces gonadotropin-releasing
hormone (GnRH), which travels to the pituitary where it stimulates
the release of follicle stimulating hormone.
Fertility
drugs, such as Lupron and Ganirelex, inhibit
GnRH production thus reducing the internal production
of FSH and blocking the LH surge. Therefore, FSH must be administered
by injection. FSH causes the recruitment of follicles, each of which
contains an egg, and supports them as they mature. As the follicles
grow they begin to produce estrogen, which travels through the bloodstream
to the hypothalamus. Estrogen also stimulates the development of the
endometrium.
Fertility drugs (FSH) like Gonal-F, Follistim, and Bravelle
are administered during an IVF cycle to stimulate
the recruitment and development of numerous eggs,
needed for IVF. Unlike Clomid which works at the hypothalamus, FSH
stimulates the ovaries directly.
Fertility drugs, such as Lupron and
Antagon, influence the actions of GnRH allowing
the physician to control the stimulation cycle,
particularly when ovulation occurs. Rising levels of estrogen cause
the hypothalamus to reduce its production of
GnRH thus lowering FSH levels. Once the follicle(s) is mature, the
hypothalamus signals the pituitary to release a surge of LH, which
triggers ovulation.
Fertility drugs such as Pregnyl and Ovidrel are
used in IVF cycles to stimulate ovulation since
the effects of GnRH are blocked. These products have the same effect
on ovulation as LH.
Fertility drugs such as FSH must be monitored to ensure proper follicular
development and reduce the chance of side effects.
The fertility specialist carefully adjusts the
dose to insure follicular development and to
time ovulation. In an in vitro fertilization
cycle, ovulation must not occur prior to egg
retrieval or the cycle would be "lost."
Lupron
and Ganirelex are products that block the LH
surge. A women usually will not ovulate as long
as she receives one of these products. Once the physician judges that
the follicles are mature, an injection of hCG (the fertility drugs
Ovidrel, Pregnyl, or Luveris may be used) is given to mimic the natural
LH surge and egg retrieval is scheduled.
Many
fertility drugs are available to treat infertility:
- Clomid for ovulation induction.
- Gonal-F,
Follistim, Bravelle, Menopur, Repronex for
ovulation induction.
- Glucophage (metformin) may
be used in the management of polycystic ovarian
syndrome.
- Parlodel for hyperprolactinemia.
- Lupron or Ganirelix Acetate used
to prevent premature ovulation in assisted
reproductive technology cycles.
- hCG Ovidrel or Luveris used to stimulate
ovulation 36 hours prior to egg retrieval in
IVF procedures or 36 hours prior to insemination
in IUI cycles. Luveris may also be prescribed for women with
hypogonadotropic hypogonadism, which is extremely
low levels of FSH and LH.
- Birth Control Pills may be prescribed to
insure there are no "leftover follicles" from
previous cycles.
- Antibiotics used to treat
infection in the male and female.
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