It is what is termed the "milk let-down hormone." Besides stimulating
the milk glands and ducts to manufacture and secrete milk, it also plays
a role in blunting the entire menstrual and ovarian cycle so that breast-feeding
women are less likely to become pregnant. This is a survival trick
of mammals, because the survival of a baby in the past was dependent on
not having to compete with a suckling rival.
It is true that some women can become pregnant
while breast-feeding, but this only happens if ovulation occurs.
The women who get pregnant for some reason overcome the blunting effect
of prolactin and make follicles in their ovaries from which they ovulate.
An outward sign for a breast-feeding woman is whether she is having regular
periods or not while lactating. If she isn't, then she's probably
not ovulating regularly and pregnancy is unlikely; if she is, then she's
also ovulating regularly and is more likely to conceive.
This blunting of the entire menstrual cycle
can be used to a gynecologist's advantage as an important clue. One
of the questions we ask when a woman is having only rare periods is whether
there is any discharge from her breasts. A bloody discharge, of course,
is often but not always a warning signal of cancer.
But white, clear, or milky liquid expressible from the nipple is a sign
of lactation. A drop can be placed on a slide and actually sent in
as a Pap smear. Mere lactation will yield a negative Pap.
A woman with sparse periods who can express
liquid from her breasts needs a prolactin level, a blood test that can
actually tell if too much is being produced. If the prolactin level
comes back normal, then this merely means that her breasts are exquisitely
sensitive to normal amounts of prolactin. This is innocent, and all
that need be done is repeat the prolactin blood test every six months while
the patient experiences the nipple discharge. In fact, there used
to be an old profession wherein women who continued to lactate long after
weaning their own children would actually rent themselves out to women
who worked or who had difficulty breast-feeding themselves. Called
"Wet Nurses," they would breast-feed under employment. The formula
business made them extinct.
Turning to those women who are lactating because
they have too much prolactin, an elevated blood test indicates a problem
with the pituitary gland where the prolactin is made. A pituitary
adenoma is a benign glandular overgrowth in this gland that cranks out
extra prolactin, causing the problem. A woman's periods will be affected,
and with this there will be ovulation dysfunction. A high prolactin,
called "hyperprolactinemia," will then affect ovulation and cause
infertility.
If the gland continues to grow, it can cause problems in the brain.
The pituitary gland sits under the brain, over the nose, tucked between
the two trunks of the optic nerves as they make their way from the brain
to the retina. Although a pituitary adenoma is benign, it can nevertheless
cause pressure effects on brain structures as a "space-occupying" lesion.
As it grows it presses on the optic nerve, diminishing vision in those
areas of the visual fields supplied by the nerve fibers there. The
first visual fields to go will be peripheral vision. A trip to an
ophthalmologist is necessary as part of this evaluation. A Magnetic
Resonance Imaging (MRI) or CAT scan is used to actually see this benign
tumor.
It used to be that neurosurgery was done to
remove the adenoma. Because it sat under the brain, the surgical
approach was up the nose and through the floor of the skull. (It
would be unfeasable to reach it from the top of the head!)This surgery
is rare today, because the same medicine used to dry up the breasts after
delivery in those choosing to bottle-feed is also used to shrink up a pituitary
adenoma. Ironically, this drug is no longer used to dry up the breasts
after routine deliveries, because there were reports of severe complications
in hypertensive women with it. In our practice we used it to dry
up the breasts for over ten years without incident before we stopped prescribing
it, as recommended for the FDA..
But it is still a tremendously beneficial
drug in women with pituitary adenomas, saving countless neurosurgeries.
True, there are those pituitary adenomas that do not respond, but the number
of surgeries for this has plummeted. The blood level of prolactin
can be used to judge the success of the treatment (it'll fall).
The endocrine (glandular) system in a woman
is an amazing consortium of ups and downs, rises and falls, peaks and troughs,
all synchronized to keep the human race going. As mammals, lactation
is a special gift to us, and it is truly ironic that this bodily function
otherwise used for nurturing and cuddling can be one of the most dangerous
non-malignancies affecting fertility, vision, and even a woman's life.
