A pituitary tumor is an abnormal growth in the pituitary gland. This is a small gland that sits at the base of your brain behind your sinuses and above the roof of your mouth. It is connected to the hypothalamus. Both the hypothalamus and pituitary gland play important roles in your body. They produce hormones that help control how your body works.
Pituitary cancer is uncommon. In fact, most pituitary tumors, called adenomas, are not cancer (benign). Unlike cancer, they cannot spread to other parts of the body. These tumors are grouped according to their size, if they make hormones and the type of hormone they make.
Pituitary adenomas come in two sizes: Microadenomas are tumors smaller than 1 centimeter. Macroadenomas are tumors larger than 1 centimeter.
Pituitary tumors are also grouped by whether they make extra hormones. The tumors can be functional, meaning they make hormones. Or they can be nonfunctional, meaning they do not make hormones. Most pituitary tumors are functional.
Functional pituitary tumors are further grouped by the type of hormone they make. Some tumors make more than one type of hormone:
- Corticotropin (ACTH)
- Gonadotropin (LH and FSH)
- Growth hormone
- Thyroid-stimulating hormone (TSH)
Nonfunctional pituitary tumors can keep the pituitary gland from working well. Since nonfunctional tumors do not make hormones, they may not cause symptoms at first. But, once the tumor reaches a certain size, you may have headaches and trouble with vision. In some cases, large tumors can crush pituitary cells, which can lead to a drop in hormone production.