Pituitary Tumor: Introduction

What is cancer?

Cancer is when cells in the body change and grow out of control. To help you understand what happens when you have cancer, let's look at how your body works normally. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them, and die when your body does not need them any longer.

Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby areas. They can even spread to other parts of the body (metastasis).

What is pituitary cancer?

Pituitary cancers are very rare. They are so rare that cancer agencies don’t keep track of how many people get them each year. Most tumors in the pituitary gland are not cancer (benign). They are called adenomas. They don't spread to other parts of the body like cancers do.

What are pituitary tumors?

A pituitary tumor is a tumor that grows in the pituitary gland. Most of these tumors are not cancer. They are called adenomas. They don’t usually spread outside of the pituitary gland. But they can greatly affect your health. They can push on nearby parts of the brain. And they may send out excess hormones.

Pituitary adenomas are grouped in 2 ways: by their size and by the kind of hormone they make.

Size. Pituitary adenomas are grouped into 2 sizes: 

• Microadenomas are tumors that are smaller than 1 centimeter (cm).

• Macroadenomas are tumors that are bigger than 1 cm.

Both kinds of tumors can either make hormones (functional) or not make hormones (nonfunctional). Most pituitary tumors are functional. This means they make excess hormones.

Hormones. Pituitary adenomas are also grouped by whether they make excess hormones. Those that do are called functional. They are then grouped by the type of hormone they make. Functional adenomas include tumors that:

• Make prolactin

• Make growth hormone

• Make ACTH (corticotropin)

• Make gonadotropin (LH and FSH)

• Make thyroid-stimulating hormone (TSH)

Some tumors make more than 1 type of hormone. A pituitary adenoma that doesn’t make excess hormones is called nonfunctional.

Understanding the pituitary gland

The pituitary gland is a small gland located inside the skull, just below the brain. It is behind the nasal sinuses and above the roof of the mouth. The pituitary gland connects to a part of the brain called the hypothalamus. Together, the hypothalamus and the pituitary control the body’s production of many important hormones.

The pituitary gland sits in a tight, bony space. It has little room to grow or expand when swollen, or if there is a tumor.

The pituitary gland controls most of the body’s gland activity. This includes the adrenal and thyroid glands. It also includes sex hormone production. In women, it controls egg production (ovarian function). In men, it controls testosterone and sperm production in the testicles. It is also believed to be the main control gland of the body’s neuroendocrine system.

The pituitary gland has 2 parts: the back part (posterior pituitary) and the front part (anterior pituitary). The back part makes the following hormones:

• Vasopressin, also called ADH (antidiuretic hormone). This hormone lets the kidneys keep healthy amounts of water and not send it all out in urine. It can raise blood pressure by causing blood vessels to narrow or tighten.

• Oxytocin. This female hormone helps the uterus contract during childbirth. It also helps the breasts release milk when a woman is nursing.

The front part of the pituitary makes several kinds of hormones. These hormones control other glands all over the body:

• Growth hormone (somatotropin). This hormone helps a child's body grow, especially during the teen years (puberty). It also helps the liver make something called insulin-like growth factor (IGF-1). IGF-1 causes bones and other tissues to grow. Adults don’t normally make a lot of this hormone.

• Thyroid-stimulating hormone (TSH). This hormone helps the thyroid gland to grow, and to make and release the thyroid hormone. The thyroid hormone controls how your body turns food into energy (metabolism).

• Adrenocorticotropic hormone (ACTH). This hormone stimulates the adrenal gland so that it can make certain steroid hormones.

• Luteinizing hormone (LH) and follicle-stimulating hormone (FSH), called gonadotropins. In women, these hormones control the menstrual cycle and ovulation. In men, they control testosterone and sperm production.

• Prolactin. This helps make milk in a woman’s breast. It’s not clear how it works in men.  

Talk with your healthcare provider

If you have questions about pituitary tumors, talk with your healthcare provider. Your healthcare provider can help you understand more about this tumor and if it is cancer.