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Causes of Infertility- Ovarian
and Unexplained Infertility
Ovarian Factor Infertility
Women are born with all their eggs for a
lifetime. After puberty, one or more of these eggs develop(s)
and are ovulated during the monthly menstrual cycle.
Once a woman reaches menopause, the eggs have lost their
ability to fertilize.  Menopause
usually occurs around age 43 but can occur later, or much
earlier as in premature ovarian failure. In general, egg
quality begins to decline around the age of 35 and the
decline continues until menopause. Many women with ovarian factor infertility are candidates for our North Carolina donor egg program.
Ovulation is governed by a complex series
of hormonal interactions and must occur regularly for
pregnancy to result. We provide a basic discussion of ovulation here,
which enables visitors to understand the events associated
with ovulation and ovarian aging.
During the first few days of the menstrual
cycle, the hypothalamus (a small gland located at the
base of the brain) produces gonadotropin-releasing hormone
(GnRH), which stimulates production of follicle stimulating
hormone (FSH) by the pituitary.
FSH stimulates the ovaries directly to cause
the recruitment of eggs within the ovarian follicles.
Continued levels of FSH are needed to support egg development. Fertility drugs such as FSH (Gonal-F, Repronex, Follistim, Bravelle, Menopur) stimulate recruitment and development of the eggs within the ovarian follicles.
As healthy eggs develop, they begin to produce estrogen,
which travels through the bloodstream and is “monitored”
by the hypothalamus.The hypothalamus/pituitary is similar to
a thermostat as it controls the blood levels of many hormones
based upon chemical feedback.
In our example, as
estrogen levels increase near ovulation the pituitary
gland produces less FSH, thereby limiting the number of
eggs that are developed. Other interactions include ovulation,
which is stimulated when the hypothalamus releases GnRH
to signal the pituitary gland to release a surge in luteinizing
hormone (LH).
As eggs loose their ability to fertilize
and develop, the day 3 level of FSH increases. Levels
above 12 mIU/ml indicate diminished ovarian reserve and
that pregnancy is unlikely using the patient’s eggs.
Thanks to donor
egg programs, women of almost any age can become pregnant
using donated eggs, as long as their general health is
good.
Irregular Ovulation- Causes
Ovulation must occur regularly for pregnancy
to result. Many conditions can cause a woman to
ovulate irregularly, or not at all, and include:
- Elevated
levels of the hormone prolactin. Prolactin is the
“breast milk” hormone that rises naturally
during pregnancy. Elevated prolactin in the absence
of pregnancy leads to irregular ovulation.
- Polycystic ovarian
syndrome- PCOS is a common cause of infertility
characterized by elevated androgens (male hormones)
and hyperinsulinemia (chronically elevated insulin levels).
- Abnormal (too high or too low) thyroid
hormone levels.
- Excessive stress or exercise.
- Abnormal production of FSH or LH.
- Premature ovarian failure.
Oftentimes, Clomid
or FSH, are
effective in establishing ovulation. When FSH stimulation of the ovaries fails to produce viable eggs, our NC donor egg program may be the next treatment step.
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