is a prolactinoma?
A prolactinoma is a benign tumor of the pituitary gland
that produces a hormone called prolactin. It is the most common
type of pituitary tumor. Symptoms of prolactinoma are caused by
too much prolactin in the blood (hyperprolactinemia) or by pressure
of the tumor
on surrounding tissues.
Prolactin stimulates the breast to produce milk during pregnancy.
After delivery of the baby, a mother's prolactin levels fall unless
she breast feeds her infant. Each time the baby nurses, prolactin
levels rise to maintain milk production.
What is the pituitary gland?
The pituitary gland, sometimes called the master gland,
plays a critical role in regulating growth and development, metabolism
and reproduction. It produces prolactin and a variety of other key
hormones. These include growth hormone, which regulates growth;
ACTH (corticotropin), which stimulates the adrenal glands to produce
cortisol; thyrotropin, which signals the thyroid gland to produce
thyroid hormone; and luteinizing hormone and follicle-stimulating
hormone, which regulate ovulation and estrogen and progesterone
production in women, and sperm formation and testosterone production
The pituitary gland sits in the middle of the head in a bony box
called the sella turcica.
The eye nerves sit directly above the pituitary gland. Enlargement
of the gland can cause
local symptoms such as headaches or visual disturbances. Pituitary
tumors may also impair production of one or more pituitary hormones,
causing reduced pituitary function (hypopituitarism).
How common is prolactinoma?
Autopsy studies indicate that 25 percent of the U.S. population
have small pituitary tumors. Forty percent of these pituitary tumors
produce prolactin, but most are not considered clinically significant.
Clinically significant pituitary tumors affect the health of approximately
14 out of 100,000 people.
What causes prolactinoma?
Although research continues to unravel the mysteries of disordered
cell growth, the cause of pituitary tumors remains unknown. Most
pituitary tumors are sporadic--they are not genetically passed from
parents to offspring.
What are the symptoms of prolactinoma?
In women, high blood levels of prolactin often cause infertility
and changes in menstruation. In some women, periods may disappear
altogether. In others, periods may become irregular or menstrual
flow may change. Women who are not pregnant or nursing may begin
producing breast milk. Some women may experience a loss of libido
(interest in sex). Intercourse may become painful because of vaginal
In men, the most common symptom of prolactinoma is impotence. Because
men have no reliable indicator such as menstruation to signal a
problem, many men delay going to the doctor until they have headaches
or eye problems caused by the enlarged pituitary pressing against
nearby eye nerves. They may not recognize a gradual loss of sexual
function or libido. Only after treatment do some men realize they
had a problem with sexual function.
What other conditions cause prolactin levels to
In some people, high blood levels of prolactin can be traced
to causes other than a pituitary tumor.
Medications - some medications can cause lactation. Prolactin secretion
in the pituitary is normally suppressed by the brain chemical, dopamine.
Drugs that block the effects of dopamine at the pituitary or deplete
dopamine stores in the brain may cause the pituitary to secrete
prolactin. These drugs include the major tranquilizers trifluoperazine
(Stelazine) and haloperidol (Haldol); metoclopramide (Reglan), used
to treat gastroesophageal reflux and the nausea caused by certain
cancer drugs; and less often, alpha methyldopa and reserpine, used
to control hypertension.
Increased prolactin levels are often seen in people with hypothyroidism,
and doctors routinely test people with hyperprolactinemia for hypothyroidism.
Breast stimulation also can cause a modest increase in the amount
of prolactin in the blood.
Other tumors arising in or near the pituitary-such as those that
cause acromegaly or Cushing's syndrome-may block the flow of dopamine
from the brain to the prolactin-secreting cells.
What tests are done in patients with a prolactinoma?
A doctor will test for prolactin blood levels in women
with unexplained milk secretion (galactorrhea), or irregular menses
or infertility, and in men with impaired sexual function and in
rare cases, milk secretion. If prolactin is high, a doctor will
test thyroid function and ask first about other conditions and medications
known to raise prolactin secretion. The doctor will also request
an MRI, which is the most sensitive test for detecting pituitary
tumors and determining their size. MRI scans may be repeated periodically
to assess tumor progression and the effects of therapy. Computer
Tomography (CT scan) also gives an image of the pituitary, but it
is less sensitive than the MRI.
In addition to assessing the size of the pituitary tumor, doctors
also look for damage to surrounding tissues, and perform tests to
assess whether production of other pituitary hormones is normal.
Depending on the size of the tumor, the doctor may request an eye
exam with measurement of visual fields.
How is prolactinoma treated?
The goal of treatment is to return prolactin secretion to normal,
reduce tumor size, correct any visual abnormalities and restore
normal pituitary function. In the case of very large tumors, only
partial achievement of this goal may be possible. Because dopamine
is the chemical that normally inhibits prolactin secretion, doctors
first treat prolactinoma with bromocriptine, a drug that acts like
dopamine. This type of drug is called a dopamine agonist. It shrinks
the tumor and returns prolactin levels to normal in approximately
80 percent of patients.
To avoid side effects such as nausea and dizziness, it is important
for bromocriptine treatment to start slowly. An example of a typical
approach used by an experienced endocrinologist follows:
Begin by taking a quarter of a 2.5 milligram tablet of bromocriptine
with a snack at bedtime. After 3 days, increase the dose to a quarter
of a tablet with breakfast and a quarter at bedtime. After 3 more
days, take half a tablet twice a day, and 3 days later, one tablet
at night and half with breakfast. Finally, the dose is increased
to one tablet twice a day. If prolactin is still high, add half
a tablet with lunch. If the medication is well tolerated, increase
the dose to a full tablet. If side effects develop with a higher
dose, return to the previous dosage. With time, side effects disappear
while the drug continues to lower prolactin.
Bromocriptine treatment should not be interrupted without consulting
a qualified endocrinologist. Prolactin levels often rise again in
most people when the drug is discontinued. In some, however, prolactin
levels remain normal, so the doctor may suggest reducing or discontinuing
treatment every two years on a trial basis.
Pergolide Mesylate (Permax)
A ergoline derivative, pergolide mesylate, effectively inhibits
PRL secretion and is an option for the medical treatment of prolactinomas.
This dopamine agonist is approximately 100 times more potent than
BC and suppresses PRL secretion for up to 24 h after a single dose
(7, 8), allowing effective control of hyperprolactinemia with once
daily dosing. Pergolide is approved in the United States only for
the therapy of Parkinson’s disease, where it has been used
safely at doses more than 10 times those used for PRL-secreting
A newer Treatment for prolactinoma's
(cabergoline tablets) is another treatment for prolactinoma's
It was approved in January 1997 by Pharmacia & Upjohn
In a clinical trial involving approximately 450 subjects, Dostinex
was compared with bromocriptine in treating hyperporlactinemia.
In the eight-week, double blind trial, prolactin levels returned
to normal in 77% of subjects treated with Dostinex (0.5mg twice
weekly) compared to 59% of those treated with bromocriptine (2.5
mg twice-daily). Restoration of menses occurred in 77% of women
treated with Dostinex, compared to 70% of those treated with bromocriptine.
Among subjects with galactorrhea (excessive breast milk discharge),
the symptom disappeared in 73% of those treated with Dostinex, compared
to 56% of 231 subjects taking bromocriptine.
Surgery should be considered if medical therapy
cannot be tolerated or if it fails to reduce prolactin levels, restore
normal reproduction and pituitary function and reduce tumor size.
If medical therapy is only partially successful, this therapy should
continue, possibly combined with surgery or radiation.
The results of surgery depend a great deal on tumor size and prolactin
level as well as the skill and experience of the neurosurgeon. The
higher the prolactin level, the lower the chance of normalizing
serum prolactin. In the best medical centers, surgery corrects prolactin
levels in 80 percent of patients with a serum prolactin less than
250 ng/ml. Even in patients with large tumors that cannot be completely
removed, drug therapy may be able to return serum prolactin to the
normal range after surgery. Depending on the size of the tumor and
how much of it is removed, studies show that 20 to 50 percent will
recur, usually within five years.
How do I choose a skilled neurosurgeon?
Because the results of surgery are so dependent on the skill and
knowledge of the neurosurgeon, a patient should ask the surgeon
about the number of operations he or she has performed to remove
pituitary tumors, and for success and complication rates in comparison
to major medical centers. The best results come from surgeons who
have performed many hundreds or even thousands of such operations.
What effect does prolactinoma have on pregnancy and use of oral
If a woman has a small prolactinoma she can conceive and have a
normal pregnancy after successful medical therapy.
During normal pregnancy in women without pituitary disorders the
pituitary enlarges and prolactin production increases. Women with
prolactin-secreting tumors may experience further pituitary enlargement
and must be closely monitored during pregnancy. Damage to the pituitary
or eye nerves occurs in less than one percent of pregnant women
with prolactinoma. However, in women with large tumors, the risk
of damage to the pituitary or eye nerves is greater. Some doctors
consider it as high as 25 percent. If a woman has completed a successful
pregnancy, the chances of her completing further successful pregnancies
is extremely high.
A woman with a prolactinoma should discuss her plans to conceive
with her physician, so she can be carefully evaluated prior to becoming
pregnant. This evaluation will include a magnetic resonance imaging
(MRI) scan to assess the size of the tumor and an eye examination
with measurement of visual fields. As soon as a patient is pregnant,
her doctor will usually advise that she stop taking "Parledol"
bromocriptine or "Dostinex"cabergoline.
Most endocrinologists see patients every two months throughout
the pregnancy. The patient should consult her endocrinologist promptly
if she develops symptoms-particularly headaches, visual changes,
nausea, vomiting, excessive thirst or urination, or extreme lethargy.
Bromocriptine treatment may be renewed and additional treatment
may be required if the patient develops symptoms from growth of
the tumor during pregnancy.
At one time, oral contraceptives were thought to contribute to
the development of prolactinomas. However, this is no longer thought
to be true. Patients with prolactinoma treated with bromocriptine
may also take oral contraceptives. Similarly, post-menopausal estrogen
replacement is safe in patients with prolactinoma treated with medical
therapy or surgery.
Is osteoporosis a risk in women with high prolactin
Women whose ovaries produce inadequate estrogen are at
increased risk for osteoporosis. Hyperprolactinemia can cause reduced
estrogen production. Although estrogen production may be restored
after treatment for hyperprolactinemia, even a year or two without
estrogen can compromise bone strength and these women should protect
themselves from osteoporosis by increasing exercise and calcium
intake through diet or supplementation, and by avoiding smoking.
Women may want to have bone density measurements to assess the effect
of estrogen deficiency on bone density. They may also want to discuss
estrogen replacement therapy with their physician.