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Scientists do not know exactly what causes most pituitary
tumors. During the past few years, they have made great progress in
understanding how certain changes in a person's DNA can cause cells in
the pituitary to produce a tumor. DNA is the molecule that carries the
instructions for nearly everything our cells do. We usually resemble
our parents because they are the source of our DNA. However, DNA
affects more than our outward appearance. It also determines our risk
for developing certain diseases, including some types of cancer.
Some genes (parts of our DNA) contain instructions for
controlling when our cells grow and divide. Some genes that promote
cell division are called oncogenes.
Other genes that slow down cell division or cause cells to die at the
right time are called
tumor suppressor genes. It is known that cancers can be
caused by DNA mutations (defects) that turn on oncogenes or turn off
tumor suppressor genes.
Some people with cancer have inherited DNA mutations (abnormal
changes in their DNA) from a parent, which increases their risk for
developing the disease. Usually, DNA mutations occur during life rather
than having been inherited. Acquired mutations of some organs may
result from exposure to radiation or carcinogens (cancer-causing
chemicals). Sometimes mutations occur for no apparent reason.
The DNA mutations that cause tumors in some people with
pituitary tumors have been identified (see the previous section on risk
factors).Members of families with these genetic syndromes can have
genetic testing to find out if they are affected.
Much less is known about the causes of non-hereditary
pituitary tumors, although some of these have acquired mutations in the
AIP gene. Some studies indicate about 40% of growth hormone-secreting
adenomas have an acquired mutation in a specific protein called Gs
alpha. Gs alpha mutations are much less common in other types of
pituitary adenomas.
Several other genetic abnormalities have been found in other
types of pituitary adenomas, but it is not clear whether abnormal genes
are essential for pituitary tumor formation. What is known is that
there is a loss of the normal regulatory mechanism that keeps the
glandular cells from overproducing their hormone and growing. This is
probably the result of the gene alterations.
Last Medical Review: 02/17/2009
Last Revised: 02/17/2009
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