More About Pituitary Tumors Minus iconIcon indicating subtraction, or that the element can be closed. Plus IconIcon indicating addition, or that the element can be opened. Arrow (down) icon.An arrow icon, usually indicating that the containing element can be opened and closed.

Pituitary Adenomas

Pituitary adenomas are the most common tumor type in the pituitary gland. “Adenoma” refers to a benign tumor that begins in glandular tissue. Pituitary adenomas can become cancerous (called pituitary carcinomas), but these cases are extremely rare.

Adenomas can also arise in other areas of the body besides the pituitary gland, including the colon and the adrenal glands.

Doctors diagnose these tumors according to their size and the type of hormones they secrete, if any.

Pituitary Microadenomas

Microadenomas are tumors that measure smaller than 1 centimeter in diameter. Most pituitary adenomas are microadenomas and often do not cause symptoms. Microadenomas are usually found during an MRI to screen for another health condition.

Pituitary Macroadenomas

Macroadenomas are defined as glandular tumors that measure larger than 1 centimeter in diameter. Pituitary macroadenomas tend to produce more symptoms than microadenomas as they are more likely to put pressure on the brain and pituitary gland. For example, people with macroadenomas are more likely to have vision loss because of pressure on the optic nerves.

Other vision problems that macroadenomas can cause include:

  • narrowing field of vision (bitemporal hemianopsia)
  • blurry vision
  • colors seeming less bright
  • double vision

Large tumors can also create hormone deficiencies when the tumor puts pressure on the pituitary gland, blocking the production of certain hormones. Learn more about hormone-related symptoms of a pituitary tumor.

Functioning Pituitary Adenomas

Functioning pituitary adenomas are pituitary tumors that produce hormones. They are the most common type of pituitary adenoma and the most common type of pituitary tumor overall. Functioning adenomas can be microadenomas or macroadenomas.

Functioning adenomas are classified according to the type of hormone they produce.

Find more in-depth information about hormone-secreting pituitary adenomas.