Your doctor thinks you may have
a pituitary tumor. Pituitary tumors are benign (non-cancerous) overgrowth
of cells that make up the pituitary gland (the master gland that
regulates other glands in the body). These tumors are very common.
Up to 25% of the population may have a tiny tumor. Tumors that grow
large enough to produce symptoms are much less common but still
are one of the most common tumors occurring within the head. These
tumors may often be present for years without diagnosis or even
symptoms.
Anatomy
The sella is a depression in the sphenoid bone that makes up part
of the skull base located behind the eye sockets.
The pituitary gland lies within the sella connected
to the brain above (the hypothalamus) by the pituitary stalk or
infundibulum. The pituitary gland sits just above the sphenoid sinus
and between the cavernous sinuses containing the two carotid arteries
and the nerves responsible for facial sensation and moving the eyes
and eyelid). The optic nerves coming from each eye meet just above
the sella in the optic chiasm.
Physiology
The pituitary gland is responsible for sending signals to the other
endocrine glands throughout the body including the thyroid gland,
the adrenal glands, and the sexual organs. The pituitary gland in
turn is controlled by signals from the hypothalamus. An abnormal
growth of cells within the pituitary gland may produce an excess
of signal to the other endocrine glands leading to overproduction
of thyroid, cortisone, or sex hormones. A pituitary tumor may cause
damage to the remainder of the gland and result in decrease in normal
pituitary function. If the pituitary tumor extends out of the sella
it may produce symptoms due to compression of surrounding structures
including the optic nerves, chiasm, and cranial nerves in the cavernous
sinus (controlling eye movement and facial sensation).
Symptoms
Patients with pituitary tumors often have no symptoms at all. Occasionally
these tumors may produce headaches. Head pain may be sudden and
severe if there is a bleed into the tumor. Endocrine symptoms are
most common including alterations in menstruation, lactation (milk
from the breast), impotence, or loss of sex drive. Less commonly,
tumors may produce growth hormone causing giantism in young patients
or enlargement of hands, feet, and facial features (acromegaly)
in older patients. Rare tumors lead to secretion of excess thyroid,
producing tremors, weight loss, diarrhea, and a sense of constantly
feeling hot. Cushing's syndrome occurs when there is excess adrenal
secretion resulting in weight redistribution from the arms and legs
to the trunk, thinning of the skin, rounding of the face (chipmunk
facial appearance), fatigue, and hair thinning. When the back portion
of the pituitary gland is affected the patient may notice excessive
thirst and urination. This is called diabetes insipidus and is unassociated
with elevated blood sugar or the need for insulin. Some pituitary
tumors are associated with diabetes and blood sugar should always
be checked.
The third set of symptoms relates to damage to surrounding structures
if the tumor gets large enough. The most common of these symptoms
is due to compression of the optic nerves or chiasm. Patients with
involvement of one optic nerve may notice dim, dark, or blurred
vision. Occasionally this may come on suddenly or be noted when
one happens to cover one eye and notes that they can't see out of
the opposite eye. If the chiasm is affected, vision will be lost
off to the outside in both eyes.
This may not be apparent unless one happens to close
one eye. If the nerves surrounding the sella are affected, there
may be double vision, eyelid droop, pupil enlargement, or facial
pain and numbness.
Diagnosis
Pituitary tumors are usually suspected based on endocrine changes
but are confirmed with imaging studies. A CT scan can reveal a pituitary
tumor and may be especially sensitive to hemorrhage. MRI scanning
may be more sensitive and better define the relationship of the
tumor to the optic nerves and surrounding structures.
Blood studies to check pituitary function are essential.
Other lesions around the sella and pituitary may produce similar
symptoms and may be confused with a pituitary tumor. These include
meningiomas, craniopharyngiomas, germ cell tumors, and aneurysms.
Treatment
Not all tumors need to be treated. Tiny adenomas picked up on scans
done for other reasons that are not producing symptoms may be followed
without treatment. When the patient is symptomatic, some form of
treatment is usually indicated. The most common approach is surgery
usually performed through the nose (or up under the lip). Occasionally
(especially when the tumor is larger or extending to the side) a
surgical approach may be best through a scalp incision.
Some tumors may be responsive to medical therapy. These medicines
are designed to mimic the normal control hormones, thus causing
the cells of the tumor to shrink but not disappear. The medicine
usually needs to be continued indefinitely. Some medications that
may be effective in controlling the symptoms of excess tumor secretion
(particularly in acromegaly) are less effective in shrinking the
tumor and are commonly used in addition to surgery.
With large tumors, some tumor cells are almost always left behind
following surgery. As these tumors tend to grow slowly additional
treatment following surgery may often be put off. If there are a
lot of cells left or symptoms develop or recur, additional treatment
may be needed. This may include repeat surgery or radiation therapy.
Radiation may be delivered in fractionated form (small doses over
several consecutive days) or with focal application (stereotactic
radiosurgery via Gamma Knife or LINAC). As surgery and radiation
may be accompanied by decreased pituitary function it is very important
that hormone levels be checked periodically and replaced as necessary.
It is also important to follow vision, visual fields, and imaging
studies (MRI scan) to make sure that there is no re-growth of the
tumor. These should probably be checked at least once every one
to two years.
Frequently asked questions
Do I have a brain tumor?
While the pituitary gland is inside the head and it is connected
to the brain at the skull base, tumors of the pituitary are not
"brain tumors." They are also almost always benign (not
cancer). Distant spread to other tissues is extremely rare.
Will my vision get better?
In patients with visual loss due to compression of the optic nerve
or chiasm by a pituitary tumor the chance of visual improvement
is best predicted by the duration of the damage. This may be difficult
to tell. The presence of changes in the back of the eye (optic atrophy)
may suggest long duration. Even when there is evidence that the
changes may be long standing good recovery is possible if the pressure
on the nerves is relieved. If medical treatment is possible this
may be effective. Surgery also can result in rapid relief of compression.
I don't want to have surgery. Can't I just have
radiation treatment?
Radiation may be effective in preventing further growth of a pituitary
tumor but probably does less in terms of tumor shrinkage. Therefore,
it is usually used in addition as opposed to instead of surgery
or medical treatment. It can be effective alone if surgery is not
possible. Focal radiation treatment (Gamma Knife) cannot be used
if the tumor is pressing on the optic nerves. If the tumor can be
separated from the optic nerves then Gamma Knife is an additional
option.
Why do I have double vision?
Double vision occurs when the eyes are not pointing in the same
direction. In patients with pituitary tumors this is usually due
to problems with the nerves (3rd, 4th, or 6th cranial nerves) that
go to the muscles that move the eye. These nerves are located just
to the side of the sella and may be affected by extension of the
tumor laterally. After treatment these nerves may regain their function
and the double vision may go away. Occasionally there may be a residual
problem with eye movements. This can sometimes be helped with prisms
in glasses or eye muscle surgery. Double vision can always be treated
acutely by closing or covering one eye or fogging one lens of glasses.
Why do I need to keep going back for checks? Once the normal endocrine control of the body
has been affected by a pituitary tumor it is very important to make
sure that hormone levels remain normal and are replaced as necessary.
It is important to regularly see your endocrinologist or internist.
Large tumors, even after successful surgery, may recur even years
later. It is thus desirable to have periodic follow up of visual
function (vision and visual fields) as well as imaging studies (MRI
scan). The necessary frequency depends on your previous history
and tumor type and should be discussed with your doctors.
