Anatomy of the pituitary and sella:
The pituitary gland is a small, bean-shaped organ that sits at the base of the brain, behind the bridge of the nose. It has a large anterior lobe (gland cells that produce hormones) and a smaller posterior lobe (nerve cells that release hormones). It sits in a small pocket of bone in the base of your skull called the sella turcica. The gland is connected to the hypothalamus in the brain by the pituitary stalk. The pituitary gland is bordered on either side by the cavernous sinuses and below by the sphenoid sinus. The sphenoid sinus is an air-filled sinus that drains into the nose. The internal carotid arteries and the nerves that control eye movement lie on the sides of the pituitary. Directly above the pituitary gland is the optic chiasm, which is responsible for vision. When pituitary tumors grow they can compress the previously-mentioned structures and cause symptoms.
Known as the master gland, the pituitary controls the other endocrine glands in the body. It releases secretions into the bloodstream and provides feedback to the hypothalamus. The hypothalamus then regulates pituitary hormone levels, depending on the needs of the body.
What is a pituitary tumor?
A tumor that grows from the pituitary gland is called an adenoma. Most adenomas are benign, slow growing, and relatively common. Tiny tumors or cysts are often found on an MRI scan performed for another reason. Most of these never grow or cause symptoms. There are two types of pituitary tumors.
- Functioning pituitary tumors – secrete high levels of hormones and interfere with other body organs. These tumors behave according to their cell of origin and are named for the specific hormones they produce. For example, a prolactinoma grows from prolactin-producing cells.
- Nonfunctioning pituitary tumors – do not secrete hormones. Instead, they grow until their size and mass effect cause headache, vision loss, nausea, vomiting, or fatigue. These tumors may compress the normal pituitary gland and decrease hormone production (hypopituitarism).
Based on the size, pituitary tumors may be classified as microadenomas (less than 10mm) or macroadenomas (larger than 10mm). Large tumors can press on the optic nerves and invade the cavernous sinuses, which house the carotid arteries and the nerves involved in eye movement.
Closely related to pituitary adenomas are craniopharyngiomas and Rathke’s cleft cysts. These grow from embryonic remnant cells in the pituitary gland. Craniopharyngiomas typically grow from the pituitary stalk upward into the third ventricle and cause symptoms similar to pituitary adenomas.
What are the symptoms?
Symptoms of a pituitary tumor vary depending on its size and hormones secretion; many are asymptomatic. About 25% of pituitary tumors are nonfunctional; 75% are functional. Of hormonally active adenomas, about 50% secrete prolactin, 20% secrete growth hormone, 20% secrete adrenocorticotropic hormone, and 10% secrete multiple hormones.
- Prolactin-producing tumors: The most common pituitary tumor that causes an overproduction of the hormone that helps control sexual function. In women, the tumor can cause menstruation to stop or inappropriate production of breast milk. In men, prolactinomas may cause enlarged breasts, erectile dysfunction or impotence, infertility, decrease in body hair, and low sex drive.
- Growth hormone-producing tumors: More common in men, these tumors cause gigantism in children or acromegaly in adults. Symptoms include enlargement of the bones in the hands, feet, or face. Other symptoms include excess sweating, high blood pressure, heart disease, diabetes and arthritis.
- Adrenocorticotropic hormone producing tumors: More common in women, these tumors stimulate the adrenal gland to secrete cortisol. Excess cortisol causes Cushing’s disease, a fatty hump between the shoulders; weight gain in the face, neck, and trunk of the body; and pink or purple stretch marks on the skin. Cushing’s can also cause diabetes, menstrual irregularities, excessive hair growth, bruising, hypertension, and bone fractures from calcium depletion.
- Thyroid-stimulating hormone-producing tumors: TSH-secreting tumors can cause hyperthyroidism. Hyperthyroidism can accelerate the body’s metabolism, causing sudden weight loss, irregular heartbeat, and nervousness or irritability.
- Non-secreting tumors: these tumors have few symptoms and are difficult to recognize until they grow quite large. These tumors can press against nearby optic nerves, causing headaches or vision loss. They can also impair hormone secretion from the pituitary gland, which can cause fatigue, weakness, loss of body hair, and pale skin.
- Pituitary apoplexy: In rare instances, a pituitary tumor can suddenly bleed (hemorrhage). Symptoms include sudden onset of a severe headache and vision changes, including vision loss, double vision, or dropping of an eyelid. Pituitary apoplexy requires emergency treatment, usually with corticosteroids and often surgery.
What are the causes?
The cause of pituitary tumors is unknown. Some researches believe they occur when a cell in the pituitary gland becomes abnormal or mutates.
Multiple endocrine neoplasia type 1 (MEN 1) is a rare condition with simultaneous tumors of the pituitary, pancreas and parathyroid glands. Pituitary adenomas develop in 25% of patients with MEN 1.
Who is affected?
Pituitary tumors are common and occur in 15% of adults; most do not cause symptoms. They can occur at any age, but are more common after puberty.
How is a diagnosis made?
If you have symptoms that suggest a pituitary tumor, your physician will work with a team of specialists to confirm the diagnosis. This team may include a neurosurgeon, otolaryngologist (ear, nose, and throat surgeon), endocrinologist, ophthalmologist, radiologist, and pathologist.
First, the doctor will obtain your personal and family medical history and perform a physical exam. In addition to checking your general health, the doctor performs a neurological exam to check mental status and memory, cranial nerve function, muscle strength, coordination, reflexes, and response to pain. Other tests may include:
- MRI scan
- Endocrine evaluation: measures hormone levels in the blood or urine to detect abnormal levels caused by pituitary tumors.
- Visual field acuity test: detects vision loss and missing area in the field of view. This test measures both central and peripheral vision.
- Petrosal sinus sampling: a procedure to draw blood from the veins that drain the pituitary gland. Blood is taken and tested for ACTH levels to help diagnose Cushing’s disease.
What treatments area available?
Treatment options vary depending on the type, grade, size and location of the tumor, and your age and general health. Medication, surgery, and radiation either alone or in combination are used to treat pituitary tumors and return hormone levels to normal. It is important to seek treatment at a center that offers the full range of options including surgery, radiation, and endocrine therapy. A neurosurgeon, ENT surgeon, endocrinologist and radiation oncologist work as a team to treat pituitary tumors.
Clinical trials may also be available as a treatment option. Research is always being conducted to improve the standard of medical care and explore new drug and surgical treatments. Information about current clinical trials, including eligibility, protocol, and locations can be found on the web.
Recovery and prevention:
The size and location of the tumor is the most important factor in determining the outcome. Since it is impossible to predict whether or when a pituitary tumor may recur, periodic monitoring with MRI scans is needed to watch for changes or regrowth.
Many people with pituitary tumors are followed long-term by an endocrinologist. Hormone imbalances can be caused by the tumor itself, or may result from the treatment. An endocrinologist will monitor your hormone blood levels, outline a treatment plan and make drug adjustments when needed.
If you have any questions or would like schedule an appointment with one of our Spine Center specialists, please call 515.875.9560.
Support groups provide an opportunity for patients and their families to share experiences, receive support, and learn about advances in treatments and medications. Contact the Pituitary Network Association for support groups in your area.
Pituitary Network Association – www.pituitary.org
National Brain Tumor Society – www.braintumor.org
American Brain Tumor Association – www.abta.org