Clomid
(clomiphene citrate)
Clomid is
often the first ovulation inducing medication prescribed
by the OB/GYN. It should never by prescribed without
evaluation of the male partner. Treatment of the female
with Clomid when an undiagnosed male problem is present
could waste valuable resources and, most importantly
in older women, time.
Follicle
stimulating hormone (FSH) is produced by the pituitary
gland and directly stimulates the production of eggs
within the ovarian follicles. The pituitary gland
is "stimulated" by a complex interaction
of chemical events controlled by the hypothalamus,
a gland located at the base of the brain.
The
hypothalamus must stimulate the pituitary gland to
release follicle stimulating hormone (FSH) and leutenizing
hormone (LH) at the appropriate times for follicular
recruitment, development and ovulation to occur.
Clomid
acts upon the hypothalamus causing it to secrete gonadotropin-releasing
hormone, which stimulates the pituitary to secrete
FSH. Many factors
can cause hypothalamic insufficiencies leading to
ovulatory disorders including, excess exercise, stress,
PCO sudden weight lose, and some medications.
Clomid should not be used for more than three to six
months. The length of treatment is dependent upon
many factors including the cause(s) of infertility,
the age of the patient, her laboratory values and
other variables. The likelihood of success with clomiphene
is highest during the first three months and diminishes
thereafter.
Clomid
side effects can include visual disturbances, nausea,
cramping, and others. The most severe, and very unlikely,
side effect is ovarian hyperstimulation which is characterized
by enlarged ovaries, pain, plural effusion, possible
stoke and other symptoms. Detailed information on
potential side effects can be obtained from rxlist.com.
Clomid
can also produce multiple births. The chance of multiple
births with ovulation inducing agents is minimized
when patients are carefully followed by a specialist
trained in the administration of infertility medications.
Letrozole
(Femara)
Letrozole
is often prescribed to treat estrogen sensitive cancer
tumors because it lowers estrogen levels. It is an
aromatase inhibitor, which interferes with the production
of estrogen (lowers the levels). Endometrial tissue
is also dependent upon estrogen for growth; therefore,
letrozole may be effective in treating endometriosis.
Letrozole
is usually administered on days 5-9 of the menstrual
cycle. Since it lowers the levels of circulating estrogens,
the hypothalamus signals the pituitary to produce
additional FSH. FSH stimulates the recruitment and
development of the ovarian follicles, each of which
contains an egg.
Letrozole
is used as solo therapy or in combination with FSH.
Recent studies demonstrate that concomitant use of
letrozole with FSH reduces the amount of FSH required
for successful "quality" stimulation.
The
half-life of letrozole is much shorter than Clomid
meaning it has very little or no effect on endometrial
thickness or the cervical mucus. Clomid can cause
thinning of the endometrial lining and thickening
of the cervical mucus; letrozole does not.
Many
specialists choose letrozole as a first line ovulation-induction
agent because of reduced side effects and clinical
effectiveness. Clomid can cause visual disturbances,
nausea, diarrhea, and other side effects, which are
typically not seen with letrozole. Letrozole is also
less expensive than Clomid.
