There are several types of pituitary adenomas, and they are classified based on size:
- Pituitary microadenomas are smaller than 10 millimeters (these are more common)
- Pituitary macroadenomas are 10 millimeters or larger.
A pituitary adenoma is also classified based on whether it produces hormones or not. A functioning pituitary adenoma makes one or more of the pituitary hormones. A nonfunctioning one does not. Each type of functioning pituitary adenoma causes different symptoms, depending on the type of hormone that is being made. Examples of functioning pituitary adenomas include:
- Prolactin-producing adenomas (which account for about 43 percent of pituitary adenomas)
- Growth hormone-producing adenomas (which make up about 17 percent)
- ACTH-producing adenomas (which account for approximately 7 percent)
- Thyroid hormone-producing adenomas (which make up about 3 percent).
Nonfunctioning adenomas make up the remaining 30 percent of pituitary adenomas.
Symptoms of a pituitary adenoma can range from simple, common complaints (such as tiredness or restlessness) to more serious symptoms (such as headaches, vomiting, or dizziness).
Symptoms vary, depending on the size and location of the adenoma. If the adenoma grows large and presses on nearby parts of the brain, symptoms such as headaches or dizziness can occur. A pituitary adenoma can press on the optic nerve as well, causing problems with vision.
Symptoms also vary based on the hormones the tumor is producing.
(Click Pituitary Tumor Symptoms for more information.)