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PITUITARY TUMORS IN CHILDREN
Introduction
The
pituitary gland is a peanut-shaped gland in the brain, behind and
between the eyes. Childhood pituitary tumors, although rare, do
occur. Such tumors are usually benign, that is, non-cancerous. However,
because the pituitary gland is very important in helping to regulate
the hormones of the body, even a small disruption can have serious
effects on mood, on the ability to focus and concentrate, as well
as on growth and overall maturation. Pituitary tumors can also cause
symptoms due to pressure on other parts of the brain and may cause
headaches, dizziness, or problems with vision.
New diagnostic techniques and chemical assays or tests for specific
hormones, as well as computerized imaging tools such as magnetic
resonance tomography (MR) and computerized tomography (CT) are used
to locate and diagnose pituitary tumors. Then microsurgery, radiation
therapy, hormones, and/or drugs are used to treat pituitary tumors
in children. The effects of some tumors can also often be improved
by hormone replacement therapies. Scientists at the National Institutes
of Health and others around the world are improving the diagnosis
and therapy of pituitary tumors and learning about the molecular
mechanisms that cause these tumors. There is also a constant search
for genetic patterns and an on-going effort to develop new gene-based
therapies to prevent or treat pituitary tumors.
The Pituitary Gland
The pituitary gland is called a master gland, one that coordinates
signals for hormone production from the brain, the hypothalamus,
and from other parts of the body This gland secretes a number of
hormones that help control and respond to stress, affect brain functions,
such as the ability to focus and pay attention, and go govern growth
and sexual development, energy metabolism and the body's ability
to defend itself.
Classification
of Pituitary Tumors
Pituitary
tumors that secrete hormones take the name of the hormone they secrete
and the ending-oma. For instance, a tumor that secretes prolactin
is called prolactinoma. Other pituitary tumors secreting corticotropin
are termed corticotropinomas, and so on. Each of these tumors produces
a characteristic syndrome in patients because of excessive hormone
secretion. Tumors that do not secrete hormones can cause problems
by interfering with the functioning of the pituitary gland and by
causing pressure on other parts of the brain.
Symptoms
In general, the symptoms seen with pituitary tumors are related
to a disturbance in production of a specific hormone or group of
hormones and relate to the role the hormones play in maintaining
health and development. The symptoms of pituitary tumors vary depending
on the size and location of the tumor and whether the tumor presses
on other organs or affects the secretion of hormones. For instance,
pituitary tumors may press on the optic nerve, causing problems
with vision.
The symptoms of a pituitary tumor can range from simple common complaints
such as listlessness or restlessness to more severe symptoms such
as headaches, vomiting or dizziness. One problem in determining
whether or not a tumor is present is that every child has minor
and relatively unimportant symptoms such as restlessness or headaches
from time to time. Of course, when more distressing signs or multiple
symptoms are seen, parents and doctors search for an explanation
and more precise tests are recommended.
In older children or adolescents, other signs may be seen including
problems with normal growth and development. For instance, sometimes
young girls or boys, under age 9, experience a very early puberty,
referred to as precocious puberty. This is caused by tumors that
secrete luteinizing hormone (LH). Girls may develop breasts, have
pubic hair, and begin menstruation. Boys may find their genitals
enlarging and facial and pubic hair beginning to grow. Tumors that
secrete follicle stimulating hormone (FSH), in contrast, can retard
sexual development in both sexes and stunt growth.
If the tumor limits the secretion of gonadotropin, it can affect
the development and functioning of the ovaries and testes. Adolescent
boys may fail to enter puberty or may lose facial or pubic hair
and notice an effect on their genital size. Adolescent girls may
also fail to enter puberty or may find their breasts ' smaller,
some loss of pubic hair, and perhaps an interruption of menstruation.
Where secretion of adrenocorticotropic hormone (ACTH) is low, the
child can experience low blood sugar, fatigue, and low blood pressure,
which can cause dizziness when standing. On the other hand, with
pituitary tumors that secrete ACTH, a variety of problems can result.
These include stunted growth, delayed or stopped puberty, weight
gain, acne, purple streaks in the skin, a round red face, and a
bulge of fat on the back of or below the neck. These tumors can
also cause weakness, depression, or forgetfulness and trigger a
sudden complete or partial loss of vision.
Some pituitary tumors can disrupt the function of the thyroid gland
by secreting thyroid stimulating hormone (TSH). This in turn enlarges
the thyroid, causing a visibly large lump in the neck known as a
goiter. These tumors also cause nervousness, a rapid pulse, weight
loss, excess eating and sweating, and a sensitivity to heat.
Pituitary tumors that limit the secretion of TSH can also affect
a child in many ways, including making it harder to concentrate,
tiredness, constipation, dry skin, and a sensitivity to cold. It
may also cause girls to have irregular periods or not to menstruate
at all.
Some pituitary tumors decrease the secretion of vasopressin, the
hormone that triggers the kidney's reabsorption of water from urine.
A lack of vasopressin can cause a great thirst, excess urination,
voracious appetite accompanied by emaciation, loss of strength,
and fainting.
Other pituitary tumors secrete an excess of the hormone prolactin.
In girls who have gone through puberty, tumors that secrete the
hormone prolactin can cause the production of breast milk and stop
menstruation, while in post-pubertal boys they can cause impotence.
An excess of prolactin can also delay or stop puberty in both sexes.
A pituitary tumor that limits the secretion of growth hormone (GH)
can stunt the growth of children and cause low blood sugar, which
can induce fainting, dizziness, anxiety, and intense hunger. Growth
hormonesecreting tumors in growing children can boost growth excessively
so that, if not treated, the children can grow unusually tall.
In adolescent children who have gone through puberty, and whose
bones have stopped growing, excess GH can cause enlargement of their
feet, hands, lips, nose, and jaw, a condition referred to as acromegaly
It also can foster excess perspiration and fatigue, a widening of
the spaces between the teeth, furrows in the forehead and weakness
in the hands.
The most common type of pituitary tumor in children is due to growth
of embryonic remnants in the area of the pituitary gland and is
called craniopharyngioma. This tumor often disrupts vision by pressing
on the optic nerve. Craniopharyngiomas also cause a lack of most
pituitary hormones, prompting a combination of some of the symptoms
previously described for tumors that induce a deficiency of single
pituitary hormones.
Diagnosis and Testing
Doctors can detect larger pituitary tumors on an x-ray, computerized
tomography scan or magnetic resonance scan. Many pituitary tumors,
however, are too small to be seen on these images of the pituitary
region of the brain. To diagnose these tumors, doctors try to detect
the hormonal abnormalities with various tests. Often blood or urine
levels of specific hormones are measured within a few hours of giving
the patient compounds known to stimulate or suppress production
of the hormones.
For instance, sometimes patients are given a glucose tolerance test.
After fasting overnight, the patient drinks a sugar solution, then
has blood samples taken in which sugar or growth hormone levels
are measured. Sometimes, in order to locate a very small tumor in
the pituitary gland, an invasive procedure is required. This procedure
is called inferior petrosal sinus sampling. A radiologist inserts
special catheters from the groin veins into the vessels that drain
the pituitary gland at the top of the neck and draws blood for measurement
of the hormone that the tumor secretes.
Treatment
Doctors can successfully treat most pituitary tumors with microsurgery
performed under the magnification of a surgical microscope, radiation
therapy, surgery, drugs, or a combination of these treatments. Surgery
is the treatment of choice for tumors that enlarge rapidly and threaten
vision. The treatment plan for other pituitary tumors varies according
to the type and size of the tumor.
Depending on each individual diagnosis, a physician can prescribe
a wide variety of treatments. Sometimes treatments stimulate or
compensate for missing hormones, others reduce the production of
hormones. In some cases, drugs must be taken on a daily basis.
The National Institute of Child Health and Human Development supports
an abundance of research aimed at developing better ways to diagnose
and treat children with pituitary tumors.
Reprinted
with permission from:
The National Institute
of Child Health and Human Development
Bldg 31, Room 2A32, MSC 2425
31 Center Drive
Bethesda, MD 20892-2425
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