Causes, Incidence, and Risk Factors
The cause of pituitary tumors is still unknown. The prevalence, however, is as high as 16.7% of the adult population. Certain rare genetic conditions are associated with an increased incidence of developing of a pituitary tumor. These conditions are:
- Multiple Endocrine Neoplasia, Type I and Type IV (MEN1, MEN4)
- Familial Isolated Pituitary Adenoma, or FIPA
- Isolated Familial Acromegaly
- McCune-Albright Syndrome
- Carney Complex
A pituitary tumor causes symptoms based on:
- The size of the tumor
- The type of tumor
- Whether the tumor produces excessive amounts of a hormone
- Any changes in the normal production of pituitary hormones caused by the tumor
Tumors are classified based on the type of tissue from which they originate.
- Pituitary Adenoma: Because the pituitary is a gland, the most common tumor is a pituitary adenoma. Nearly 90% of pituitary tumors are adenomas and remain localized in the pituitary gland. Though not cancerous, pituitary adenomas can grow to a large size causing pressure on the surrounding brain structures and negatively effecting vision. If vision starts to become effected, if not treated soon enough, the patient can become permanently blind.
- Invasive Pituitary Adenoma: If a pituitary tumor spreads or metastasizes to other parts of the skull, dura,or sinuses, it is referred to as an invasive pituitary adenoma. This is also a benign tumor.
- Pituitary Carcinoma: Pituitary tumors become cancerous if the tumor invades certain parts of the nervous system, such as the brain, the subarachnoid space, or if it metastasizes anywhere else in the body. Pituitary adenomas do not become carcinomas. In this very rare situation, the tumor is classified as a pituitary carcinoma. The incidence of pituitary carcinomas is less than 0.5% of all pituitary tumors.
Pituitary tumors are further divided into two categories:
- Nonfunctioning: Tumors of the pituitary gland which do not produce hormones are considered nonfunctioning pituitary tumors. This type accounts for 65% of all pituitary tumors. The symptoms typically associated with a nonfunctioning pituitary tumors are vision loss, headache, fatigue, and decreased sexual function.
- Functioning: The pituitary gland normally produces several specific hormones. These are the adrenocorticotrophic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), growth hormone (GH), and the melanocyte-stimulating hormone (MSH). Of all pituitary tumors, 35% produce excessive amounts of one or more of these types of hormones and consequently are classified as a functioning pituitary tumor.
The most common types of pituitary functioning tumors are:
- ACTH-Producing Tumor: ACTH produces cortisol which is a hormone that regularly fluctuates with sleep-wake cycles. Stress can cause an increase in cortisol levels being secreted into the blood stream. Cortisol aids the body in regulating blood sugar levels and fighting infection. If cortisol levels become too high, however, it can lead to weight gain, slowed healing, muscle weakness, acne, easy bruising, thinning skin, and high blood pressure. Signs of the overproduction of ACTH are weight in the mid-abdominal region yet little to no weight gain in the arms and legs, diabetes, and a “buffalo hump” fat pad growth between the shoulders. Also, purple striations in the abdominal region can be visualized on physical examination. The combination of these three physical signs is referred to as “Cushing’s syndrome”.
- Prolactin-Producing Tumor: Normally, prolactin levels are increased after a woman gives birth. Prolactin stimulates the mammary glands to produce milk in order for breast feeding to be possible. A pituitary tumor can cause the release of prolactin levels into the bloodstream despite a woman not being pregnant or having recently delivered an infant. This leads to breast milk production and its discharge from the breasts. Excessive prolactin production can also cause a lack of menstruation, difficulty conceiving, and a low sex drive. In men, too much prolactin can cause a low sperm count and erectile difficulty.
- Growth Hormone Secreting Tumor: Growth hormone regulates the metabolism of sugar and fat as well as growth in stature and development. The excessive secretion of growth hormone from a pituitary tumor can cause an abnormally large sized face with prominent frontal bossing, large hands, feet, stature, and heart. The term used to describe the abnormal large growth of course facial features, hands, and feet is acromegaly. Patients with abnormally large growth are subject to joint pain, increase bone length and width, excessive sweating, and early death due to the enlarged heart which is weak and predisposed to early heart failure.
Because of the complex nature of pituitary tumors, they should be diagnosed and treated by neurosurgeons and endocrinologists working together. In most cases, patients are referred to CNSO neurosurgeons because of an abnormal MRI or Cat Scan. Our physicians prescribe detailed hormone tests, and review all existing medical imaging to properly diagnose and recommend the least invasive treatment for patients. Most importantly, they will assure the patient whether the tumor can be treated conservatively with medications or whether it will need to be surgically removed.
Questions to ask your doctor:
- What kind of pituitary tumor do I have?
- How will this tumor affect my health?
- What treatment do I need for it?
- What are the risks and benefits of each of my treatment options?
- Should I see an endocrinologist?
- Should I see an ophthalmologist?
Management and Treatment
If treatment is necessary, there are two clear objectives:
- Reduce the excessive production of hormones.
- Remove or reduce the tumor to eliminate pressure on the optic nerves and surrounding structures.
Hormone Therapy: Depending on which hormones are being overproduced by the pituitary tumor, certain medications can reduce its excessive production. The symptoms of the tumor will then resolve. CNSO neurosurgeons will be able to determine if the symptoms can be treated with medication alone. Different types of medications may be used to control how much growth hormone, prolactin, thyroid stimulating hormone, or other hormones are made. Only the pituitary tumor that secretes prolactin can be successfully treated with medication alone. Tumors that secrete prolactin are called prolactinomas. Bromocriptine is the medication used to reduce the production and secretion of prolactin. This drug will also reduce the size of the pituitary tumor. Although Bromocriptine may control the tumor, it may not cure it. Medicine as a form of treatment may need to be continued for years.
Surgery: If the pituitary tumor excessive secretions cannot be halted or if it has already grown to a size that is compromising the surrounding nerves, surgery is the best option. In order to remove a tumor, the CNSO neurosurgeon will elect the least invasive technique to access the pituitary tumor. The pituitary gland is located near the level of the base of the nose within the skull. Using advanced technology called minimally invasive endoscopic brain surgery, the neurosurgeon can access and remove the tumor via the nose. This method, commonly used for smaller tumors, is called the endoscopic transsphenoidal approach. It leaves no visable scar on the patient. If the tumor is extremely large, a craniotomy is more likely to be performed by the CNSO neurosurgeon. A craniotomy is when the neurosurgeon makes an incision in the scalp near the top of the head but within the hairline so the scar will be hidden beneath the patient’s hair. A small piece of the skull is lifted out so the surgeon can directly visualize and remove the tumor. After the tumor has been excised, the small piece of skull previously removed is securely replaced. The scalp is then closed and secured with stitches and staples.
If the tumor cannot be removed with surgery, or it continues to reoccur, radiation therapy may be offered. Radiation may also be recommended if the pituitary tumor is cancerous. Radiation therapy uses high-energy beams particles or electromagnetic waves to kill cancer cells. There are several methods by which radiation can be applied to a pituitary tumor. The goal is to direct the radiation only at the tumor while minimizing exposure of any other tissue.
Types of radiation that may be used include:
- Stereotactic radiation: This is a specialized type of external beam radiation therapy that uses focused radiation beams to precisely target the tumor. The CNSO neurosurgeons may use advance technology such as Gamma-Knife radiosurgery to externally direct radiation to the pituitary tumor without making an incision. It may be used to target difficult or hard to reach locations or if the patient has multiple medical conditions that could complicate the outcomes of the a surgery.
- Proton beam radiation: This is a unique form of radiosurgery that uses a different type of particle (or energy) beam. It can be focused directly on the pituitary tumor. This helps limit radiation to nearby healthy tissues.
The clinical course of a pituitary tumor depends on its size and type of tumor. Once treatment eliminates the tumor, patients can return to full activities and lead normal lives. Pituitary adenomas, however, can recur. If they do, additional treatment would be required. About 18% of patients with non-functioning adenomas and 25% with prolactinomas, will need additional treatment at some point. In certain instances, pituitary adenoma treatment can result in low hormone levels. If this occurs, a hormone supplement may become necessary.
Why Choose the Centers for Neurosurgery, Spine, & Orthopedics for Pituitary Tumor Treatment?
Pituitary tumors and their treatment are complex. At Centers for Neurosurgery, Spine, and Orthopedics, all pituitary care is coordinate by pituitary experts. Patients with pituitary tumors will meet with the CNSO neurosurgeons who have extensive experience in diagnosing and treating pituitary tumors. They will create a plan for a cure using the most advance yet conservative care.
The neurosurgeons at the Centers for Neurosurgery, Spine, & Orthopedics are among the most experienced and skilled experts in treating pituitary adenomas, benign pituitary tumors, or pituitary carcinomas.
If surgery is necessary, CNSO neurosurgeons are very proficient in each tumor removal technique including minimally invasive endoscopic brain surgery. They routinely provide successful outcomes for many patients. CNSO today to schedule a consultation.