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Most pituitary tumors are pituitary adenomas: benign, slow-growing tumors that arise from cells in the pituitary gland. The pituitary gland is located at the base of the brain, just behind the eyes. The pituitary gland is considered to be the master hormone gland that regulates the body's hormones.
Pituitary Adenomas: Expert Care in Southern California
Our comprehensive approach to diagnosis and treatment of pituitary conditions sets the UCLA Pituitary Tumor Program apart. Our physicians treat a high volume of patients every year and perform over 100 pituitary surgeries a year, making us one of the top programs in the United States.
Learn more about pituitary adenomas:
Pituitary Adenomas: Physiology
The pituitary gland has different types of pituitary cells, each producing special hormones released into the bloodstream that affect other organs in the body.
Pituitary tumors originate from one of these specialized cells. If the tumor cells produce an excess of one or more hormones, it is called a "functional" adenoma. Examples of functional adenomas include:
- Prolactinoma, a tumor that overproduces prolactin
- Acromegaly (adults) gigantism (child), caused by an excess growth hormone
- Cushing's disease, caused by a pituitary tumor stimulating an overproduction of cortisol
Pituitary tumors that do not secrete active hormones are called clinically nonfunctioning adenomas.
Incidence of Pituitary Adenomas
Pituitary adenomas are relatively common. Tiny, microscopic pituitary adenomas are found in one in five adults. However, most of these tumors never grow or cause problems. Often, a patient is undergoing a magnetic resonance imaging (MRI) scan of the brain for another reason, and the doctor discovers a pituitary adenoma.
Types of Pituitary Adenomas
Pituitary adenomas are classified in several different ways depending upon their properties:
- Size. A microadenoma is less than one centimeter in size; a macroadenoma is one centimeter or greater in size.
- Aggressiveness. Nearly all pituitary adenomas are benign (noncancerous) and slow growing. An atypical pituitary adenoma, the rarer type, grows more quickly and is more likely to recur. Pituitary carcinomas (a malignant tumor) spread to other parts of the body, and are extremely rare.
- Hormone secretion. Pituitary adenomas that release an active hormone (usually an excessive amount) are called hormonally active or functional tumors. If they do not release an active hormone, they are called clinically non-functioning adenomas.
Most pituitary adenomas occur spontaneously, meaning they are not inherited.
There are cases of familial pituitary tumors, which is an inherited tendency to develop pituitary adenomas. However, these cases are uncommon. In many familial cases gigantism or a young onset of acromegaly is more common.
Multiple endocrine neoplasia type 1 (MEN 1) is a rare condition characterized by simultaneous tumors of the pituitary, pancreas and parathyroid glands. Pituitary adenomas develop in 25 percent of patients with MEN 1.
The symptoms that pituitary adenomas produce depend upon several factors, including whether the tumors are hormone-producing or clinically nonfunctioning.
- Hormone-producing pituitary adenomas release an active hormone in excessive amounts into the bloodstream. Patients usually experience symptoms related to the hormone action on the body.
- Clinically nonfunctioning pituitary adenomas typically cause problems related to the size of the tumor, which pushes on surrounding brain structures.
- Large pituitary tumors can compress the optic chiasm, the crossing point of the optic nerves, leading to vision loss.
- Large pituitary tumors can also compress the normal pituitary gland and cause pituitary failure. This is why is it important to obtain a comprehensive evaluation of pituitary function if a pituitary tumor is diagnosed.
Hormone-producing pituitary tumors can also grow to large sizes, causing the same problems described above in addition to the hormone-related effects.
Symptoms related to overproduction of hormones
- Growth hormone-secreting pituitary adenoma. An excessive production of growth hormone (GH) causes acromegaly in adults or gigantism in children. Symptoms include enlarged hands and feet and other changes in the body.
- ACTH-secreting pituitary adenoma. Excessive ACTH hormone production causes Cushing's disease. Symptoms include unexpected weight gain, easy bruising of the skin and muscle weakness.
- TSH-secreting pituitary adenoma (thyrotropinoma). Excessive TSH hormone production leads to hyperthyroidism. These tumors are very rare.
Symptoms related to effect of a large pituitary adenoma (macroadenoma)
- Vision loss. This occurs when macroadenomas grow upward into the brain cavity, compressing the optic chiasm.
- A loss of the outer peripheral vision, called a bitemporal hemianopsia
- Many patients do not become aware of their visual loss until it is quite severe.
- Other visual problems can include:
- Loss of visual acuity (blurry vision), especially if the macroadenoma grows forward and compresses an optic nerve.
- Colors not perceived as bright as usual
- Loss of pituitary function (see below)
Symptoms related to pituitary insufficiency
When the tumor compresses the normal pituitary gland, it can cause it to fail leading to pituitary insufficiency (hypopituitarism). The symptoms will depend upon which hormone is involved.
- Reduction of sex hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
- In men, this can lead to a low testosterone level, causing decreased sexual drive and impotence.
- In some cases, there can be loss of body and facial hair.
- In women, this can lead to infertility.
- Reduction in TSH production can lead to hypothyroidism, which can cause appetite loss, weight gain, fatigue and decreased mental function.
- Reduction in ACTH production causes adrenal insufficiency, because cortisol production is reduced. Symptoms include fatigue, low blood pressure, electrolyate abnormalities. If severe, death can occur.
- Reduction in growth hormone (GH) production is called growth hormone insufficiency.
- In children, this results is stunted growth and delayed puberty.
- In adults, the effects can be subtle but can include generalized tiredness, loss of muscle mass and tone.
- Reduction in prolactin production is uncommon and occurs with severe pituitary insufficiency.
- Large pituitary tumors can slightly elevate blood prolactin levels. Doctors think this occurs because of compression of the pituitary stalk, the connection between the pituitary gland and the brain. It is called the "stalk effect."
- In premenopausal women, this can lead to reduction or loss of menstrual periods and/or breast milk production (galactorrhea).
- Prolactin levels are only slightly elevated, as opposed to prolactinomas in which the prolactin level is usually very high.
Pituitary adenomas can suddenly bleed internally (hemorrhage), leading to an abrupt increase in size. In other cases, the tumor can outgrow its blood supply, leading to swelling of the dead tissue. These scenarios are termed "pituitary apoplexy."
Patients with pituitary apoplexy generally experience a sudden headache. If accompanied by acute vision loss, this is a surgical emergency. Pituitary apoplexy can also lead to severe pituitary insufficiency, the symptoms of which can occur days to weeks later.
A pituitary adenoma may be suspected based on symptoms, the medical history, and physical findings. Explaining your symptoms is a crucial part of diagnosis, as your doctor uses the information to determine whether a pituitary tumor is secreting an excess of hormones and if there is evidence of pituitary insufficiency.
Standard diagnostic tests include:
Hormone testing can detect or confirm a functional adenoma, as well as determine if there is evidence of pituitary insufficiency. Some functional tumors, particularly prolactinomas, can effectively be treated without surgery and therefore it is very important that comprehensive hormone testing be performed prior to the consideration of surgical removal of the tumor. An endocrinologist who specializes in pituitary tumors will help interpret the results of the test.
Imaging Scans for Pituitary Adenomas
One method we use to detect pituitary adenomas is a magnetic resonance imaging (MRI) scan. An MRI can reliably detect adenomas larger than four millimeters. We use a special pituitary protocol to help obtain an accurate image. In some cases, a powerful 3T (Tesla) MRI scanner may detect even smaller tumors not visible during a regular MRI scan. MRI is the preferred imaging scan for detecting pituitary adenomas, though sometimes a computed tomography (CT) scan is used.
A neuroradiologist specializing in pituitary tumor imaging may help in finding very small tumors, particularly in Cushing's disease.
There are other tumors that produce symptoms similar to that of a pituitary adenoma. Your doctor will want to rule out these other tumors before confirming a diagnosis. Tumors that mimic the symptoms of a pituitary adenoma include:
- Rathke's cleft cyst
- Arachnoid cyst
- Granulomatous diseases
- Glioma of the suprasellar region
- Metastatic tumor
Treating a pituitary adenoma depends on several factors, including:
- Hormone production by the tumor (if present)
- Tumor size
- The extent that the tumor invaded surrounding structures
- Your age and general health
Ideally, more than one specialist is involved in managing the treatment of pituitary adenomas. Our dedicated Pituitary Tumor Program includes specialists in many different fields, working together to ensure the best outcomes for you.
Medical Management of Pituitary Adenomas
If you have a hormone-producing pituitary adenoma, it can sometimes be treated medically. An endocrinologist who specializes in hormone-producing tumors, called a neuro-endocrinologist, may be necessary in managing your care. He or she can also provide enrollment in clinical trials if standard treatments are insufficient.
Medication can help certain pituitary tumors:
- Prolactinomas are often treated only with medication and may not require surgery.
- Medication plays an important role in managing Cushing's disease and acromegaly.
It is also important to address pituitary failure (hypopituitarism), especially prior to surgery. Inadequate cortisol or thyroid levels can be life threatening if they are not treated before surgery.
Surgery for Pituitary Adenomas
If the pituitary adenomas require surgery, typically the best procedure is through a nasal approach. Our neurosurgeons who specialize in pituitary tumor surgery are experts in the minimally invasive endoscopic endonasal technique. This procedure removes the tumor while minimizing complications, hospital time and discomfort. This advanced technique requires specialized training and equipment.
Very large tumors that extend into the brain cavity may require opening the skull (craniotomy) to access the tumor. Our surgeons are also experts in the minimally invasive "key-hole" craniotomy, utilizing a small incision hidden in the eyebrow.
Radiation Therapy for Pituitary Adenomas
Some tumors cannot be removed surgically and may not respond to medications. Radiation therapy can be effective in controlling the growth of these tumors.
We use an advanced method of radiation therapy called stereotactic radiosurgery. This is a carefully sculpted radiation beam that delivers a high dose of radiation to the tumor target; the surrounding brain structures receive only a fraction of the radiation. The healthy structures are typically unharmed, with the exception of the pituitary gland.
A consequence of radiation treatment is that it can cause delayed pituitary failure. This typically occurs several years after treatment. If this happens, you will require hormone replacement.
The UCLA Pituitary Program offers numerous clinical trials, testing new therapies for pituitary adenomas.
To schedule an appointment with one of our physicians at the Pituitary Tumor Program, please call (310) 825 5111.
You can also email us at [email protected]