Prolactinomas
Prolactinoma is a benign tumor (adenoma) of the pituitary
gland that produces a hormone called prolactin.
It is the most common type of pituitary tumor.
Epidemiology
Prolactin is a hormone that triggers the breasts to produce
milk (lactation).
Prolactinoma is the most common type of pituitary tumor
(adenoma). It makes up at least 30% of all pituitary adenomas.
Almost all
pituitary tumors are noncancerous (benign). Prolactinoma may occur as part of
an inherited condition called multiple endocrine neoplasia type 1 (MEN 1)
Prolactinomas occur most commonly in people under age 40.
They are about five times more common in women than in men, but are rare in
children.
At least half of all prolactinomas are very small (less than
1 cm or 3/8 of an inch in diameter). These small tumors are more common in
women.
They stay small and never get larger.
Larger tumors are more common in men. They tend to occur at
an older age.
The tumor can grow to a large size before symptoms appear.
The tumor is often detected at an earlier stage in women
than in men.
Medicines that treat low thyroid function (hypothyroidism)
and mental illnesses can raise prolactin level.
This can cause symptoms similar
to prolactinoma or an actual prolactinoma.
Symptoms:
Symptoms of prolactinoma are too much prolactin in the blood
(hyperprolactinemia) or caused by pressure of the tumor on surrounding tissues.
In women:
Abnormal milk flow from the breast in a woman who is not
pregnant or nursing (galactorrhea)
Breast tenderness
Decreased sexual interest
Decreased peripheral vision
Headache
Infertility
Stopping of menstruation not related to menopause, or
irregular menstruation
Vision changes
In men:
Decreased sexual interest
Decreased peripheral vision
Enlargement of breast tissue (gynecomastia)
Headache
Impotence
Infertility
Vision changes
Symptoms caused by
pressure from a larger tumor may include:
HEADACHE
Lethargy
Nasal drainage
Nausea and vomiting
Problems with the sense of smell
Vision changes, such as double vision, drooping eyelids or
visual field loss
There may be no symptoms, especially in men.
Those that are caused
by increased prolactin levels are:
Amenorrhea
Galactorrhea (infrequent in men)
Loss of axillary and pubic hair
Hypogonadism, gynecomastia, erectile dysfunction (in males)
Those that are caused
by mass effect are:
Bitemporal hemianopsia (due to pressure on optic chiasm)
Vertigo
Nausea, vomiting
Prolactin stimulates the breast to produce milk, and has
many other functions such as regulation of
mood.
Hence prolactin levels are
usually higher during pregnancy and after childbirth.
Each time the milk is dispensed, prolactin levels rise; this
process may cycle to maintain milk production.
In males it is responsible for the sexual refractory period
after orgasm and excess levels can lead to erectile dysfunction.
Classification
Based on size, a prolactinoma can be classified as a microprolactinoma
(<10 mm diameter) or macroprolactinoma (>10 mm diameter).
Microprolactinomas are much more common than
macroprolactinomas.
Diagnosis:
Prolactin blood levels
Imaging studies: Brain MRI and CT Scan
In addition to assessing the size of the pituitary tumor, damage
to surrounding tissues is assessed, and tests are performed 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.
Management
Medicine is usually successful in treating prolactinoma.
Some people have to take these medicines for life.
Some people can stop taking
them, especially if their tumor has disappeared from the MRI. But there is a
risk that the tumor may grow and produce prolactin again, especially if it is a
large tumor.
The goal of treatment is to return prolactin secretion to
normal, reduce tumor size, correct any visual abnormalities, and restore normal
pituitary function.
A large prolactinoma can sometimes get larger during
pregnancy.
Surgery is done in some cases when symptoms are severe such
as sudden worsening of vision.
Radiation is usually only used in patients with prolactinoma
that continues to grow or gets worse after
both medication and surgery. It may
be given in the form of:
Conventional radiation
Gamma knife or stereotactic radiosurgery -- a type of
radiation therapy that focuses high-powered x-rays on a small area in the
brain.
Dopaminergic receptor agonists ( Bromocriptine and
Cabergoline) are the first line treatment for prolactinomas including large
prolactinomas
With this treatment,the size of tumors decreases within days
and patients vision improves even before the decrease in tumor size is
appreciated on Brain MRI.
Once treatment with these medications is started,the
patients would require close monitoring of his clinical symptoms,
prolactin levels,
visual fields assessments and
MRI of his pituitary gland
Transphenoidal
and transcranial surgery is rarely required for patients with prolactinomas.
Even patients
with visual field defects and compressive symptoms may respond to treatment
with
dopaminergic
receptor agonists.
Hypogonadism
secondary to hyperprolactinemia is likely to respond to dopaminergic receptor
agoinists and
not to treatment with testosterone
