What is a Prolactinoma?
A prolactinoma is a benign, or noncancerous, tumor of your pituitary gland that produces the hormone prolactin. As the tumor grows, it will eventually cause abnormally high levels of prolactin in your blood.
- Disruption of menstrual cycle or absence of menstruation
- Infertility from lack of follicle-stimulating hormone and luteinizing hormone
- Milk production unrelated to pregnancy or nursing
- Breast tenderness
- Weak, easily injured bones and osteoporosis
- Vision changes
- Decreased size of testicles
- Decreased beard growth
- Muscle weakness
- Breast enlargement
- Milk production and secretion
- Infertility (rare)
Sometimes, especially large tumors can cause symptoms broadly associated with brain tumors, such as headache, lethargy, and vomiting.
It is possible to have a prolactinoma but not show any symptoms. Such asymptomatic prolactinomas are more common in men than in women.
Because prolactinomas are benign and sometimes stop growing on their own (especially small tumors), your doctor will help you determine if any treatment is needed other than observation. Generally speaking, treatment is indicated for the following symptoms:
- Abnormally low sex drive
- Abnormal lactation
- Decreased sex drive
Prolactinomas can often be treated successfully with prescription medicines alone. However, medications cannot cure prolactinomas, and the medication will have to be taken for the rest of your life to control the symptoms and tumor growth.
- Cabergoline is in a class of drugs known as dopamine receptor agonists. This medicine works by inhibiting the cells that produce prolactin as well as the growth of abnormal prolactinoma cells. It is the drug of choice for treating prolactinomas because it causes fewer and less serious side effects than bromocriptine.
- Bromocriptine blocks the production of prolactin by the pituitary gland and may even cause your tumor to stop growing or to shrink. It is an option if treatment with cabergoline fails or is contraindicated. However, long-term treatment with bromocriptine can cause surgical removal of your prolactinoma to be less effective. Therefore, if your doctor recommends surgery, it is best if it occurs within six months after the time you start taking bromocriptine.
Surgery is indicated in the rare event your prolactinoma fails to respond to bromocriptine or cabergoline, or if the proximity of your prolactinoma to your optic nerves causes visual disturbances or blindness.
Your surgeon will gain access to your pituitary gland using the transsphenoidal approach—so named because the route your surgeon takes crosses, or transects, your sphenoid bone. This bone is located behind your nose mostly within your skull.
Using precise surgical instruments, your surgeon will make an incision through your nasal cavity to create an opening in your sphenoid bone. Once your surgeon gains access to your sphenoid sinus (the air-filled area behind the sphenoid bone), further incisions will be made until a hole is created in the sella turcica—the bone that cradles and protects your pituitary gland.
Once your tumor appears in the operative field, removal of the tumor can proceed. Your surgeon will use high magnification to readily distinguish normal pituitary tissue from the prolactinoma.
After the tumor has been removed, your surgeon will clean the tumor cavity and seal it.
At Barrow Neurological Institute at Dignity Health St. Joseph’s Hospital and Medical Center, our surgeons specialize in two types of surgery for prolactinomas, microsurgery and endoscopic surgery:
- Microsurgery uses a powerful operating microscope to help your surgeon distinguish between tiny structures in and around your pituitary gland.
- Endoscopic pituitary surgery uses small tubes and a tiny camera to help your surgeon remove your tumor in small pieces.
Both surgeries aim to minimize trauma to the tissue surrounding your pituitary gland while facilitating a speedy recovery with as little pain or discomfort as is possible. Each technique has its own inherent advantages and disadvantages, and your surgeons will work with you to help determine which is the best fit for you.
Most patients are able to return home the day after their surgery for removing a prolactinoma, and nasal packing is seldom required.
Gamma Knife radiosurgery is a highly advanced form of radiotherapy that is used to achieve similar results to the traditional surgical techniques described above. It is usually reserved for prolactinomas that are especially resistant to medical and surgical treatments. After you are treated with Gamma Knife, it can take several years for symptoms to reside.
The ‘knife’ in this surgery is actually made up of many small beams of radiation focused on a single point. Each individual beam is too weak to damage healthy tissue, but at the point where the beams converge they deliver a dose of radiation that is lethal to the tumor.
Gamma Knife is an outpatient procedure, does not involve any incisions, and requires only brief sedation under general anesthetic.
How common are prolactinomas?
These types of hormone-producing pituitary tumors rarely run in families. Women are five times more likely to get them than men. Men are more likely to have a large prolactinoma (macroprolactinoma) while small prolactinomas (microprolactinomas) are more common in women. Prolactinomas most often occur in adults under the age of 40 years and are extremely rare in children.
How are prolactinomas diagnosed?
Your doctor can perform a blood test to determine if abnormally high levels of prolactin are present in your blood.
If your blood test shows elevated levels of prolactin, your doctor will order a magnetic resonance imaging (MRI) or computed tomography (CT) scan to determine the presence and location of the tumor in your pituitary region.