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We don’t know exactly what causes most pituitary tumors. But in recent years, researchers have made great progress in understanding how certain changes in the DNA in pituitary cells can lead to them forming a tumor.

DNA in our cells makes up our genes, which control how our cells function. We usually look like our parents because they are the source of our DNA. But our genes affect more than how we look.

Some genes normally help control when our cells grow, divide to make new cells, repair mistakes in DNA, or cause cells to die when they’re supposed to. If these genes aren’t working correctly, it can lead to cells growing out of control. For example:

• Changes (mutations) in genes that normally help cells grow, divide, or stay alive can lead to these genes being more active than they should be, causing them to become oncogenes. These genes can result in cells growing out of control.
• Genes that normally help keep cell division under control or cause cells to die at the right time are known as tumor suppressor genes. Changes that turn off these genes can result in cells growing out of control.
• Some genes normally help repair mistakes in a cell’s DNA. Changes that turn off these DNA repair genes can result in the buildup of DNA changes within a cell, which might lead to them growing out of control.

Any of these types of DNA changes might lead to cells growing out of control and forming a tumor. To learn more, see Oncogenes, Tumor Suppressor Genes, and DNA Repair Genes.

Inherited versus acquired gene mutations

Some people inherit gene mutations (changes) that increase their risk for pituitary tumors from their parents. Some of these mutations and the genetic syndromes they cause are discussed in Risk Factors for Pituitary Tumors. Members of families with these genetic syndromes can think about having genetic testing to find out if they are affected.

But often, the gene changes that lead to pituitary tumors are acquired during life, rather than having been inherited. In some types of cancer, acquired gene mutations can be caused by outside exposures, such as radiation or cancer-causing chemicals. But there are no known environmental causes for pituitary tumors. The gene changes in these tumors might just be random events that sometimes happen when a cell divides, without having an outside cause.

In pituitary tumors that don’t run in families, sometimes the tumor cells have acquired mutations in genes such as AIP, GNAS, USP8, USP48, and BRAF. These mutations are much more common in some types of pituitary adenomas than in others.

Changes in other genes have also been found in some types of pituitary adenomas, but in many cases it’s not clear which gene changes might have caused the tumor, or even if abnormal genes are always needed for pituitary tumors to form.

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.