What Causes Pituitary Tumors?

Scientists don’t 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 chemical in each of our cells that makes up our genes – the instructions for how our cells function. We usually look like our parents because they are the source of our DNA. But DNA affects more than how we look.

Some genes control when cells grow, divide into new cells, and die. Genes that help cells grow, divide, and stay alive are called oncogenes. Genes that slow down cell division or cause cells to die at the right time are called tumor suppressor genes. Tumors can be caused by DNA changes that turn on oncogenes or turn off tumor suppressor genes.

Some people inherit gene mutations (changes) from their parents that greatly increase their risk for developing pituitary tumors. Some of these mutations were described in Risk Factors for Pituitary Tumors Members of families with these genetic syndromes can have genetic testing to find out if they are affected.

But often, gene mutations occur during life rather than having been inherited. In some types of cancer, these acquired mutations can be caused by outside exposures, such as radiation or cancer-causing chemicals. Most pituitary tumors are not cancers, and there are no known environmental causes for these tumors. The gene changes in these tumors might just be random events that sometimes happen when a cell divides, without having an outside cause.

Some non-hereditary (sporadic) pituitary tumors – those that don’t run in families – have acquired mutations in a gene called AIP. Many growth hormone-secreting adenomas have an acquired mutation in a gene called GNAS1. These mutations are much less common in other types of pituitary adenomas.

Changes in other genes have been found in other types of pituitary adenomas, but it’s not clear if abnormal genes are always needed for pituitary tumors to form. What is known is that there is a loss of the regulatory mechanism that normally keeps the pituitary cells from growing and making too much hormone.

Because there are no known lifestyle-related or environmental causes of pituitary tumors, it’s important to remember that there is nothing people with these tumors could have done to prevent them.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Revised: November 2, 2017

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