The Normal Pituitary Gland
The pituitary gland is a small tear dropped shaped gland found at the base of the brain and a general overview of pituitary disease is on our website. The gland is composed of two parts which are the posterior pituitary and the anterior pituitary which communicate with the rest of the brain via a stem called the pituitary stalk . This gland sits within a small bone cavity called the sella turcica. This bone cavity is located behind the eye sockets and the nose sinuses and is therefore also close to the optic nerve, which needs to function properly for normal vision. On both sides of the sella turcica there are major blood vessels and nerves which pass nearby to the pituitary gland in an area called the cavernous sinus. The close proximity of the pituitary gland in relation to these important other organs becomes very significant if a pituitary tumor is present because there is not much extra space in this part of the brain. Review pituitary anatomy to understand the physical relationships of these brain structures.
The anterior pituitary makes many hormones:
Prolactin is a hormone that is needed to make breast milk.
ACTH controls steroids made by the adrenal gland.
TSH controls the thyroid.
Two other hormones (FSH and LH) control the sex hormones and fertility.
Growth hormone is responsible for linear growth and height in children and maintenance of bone and muscle mass in adults.
The posterior part of the pituitary is a direct extension of the brain and stores two hormones:
Antidiuretic hormone works on the kidneys to regulate water retention.
Oxytocin controls contractions when a woman goes into labor.
The pituitary gland is the key link between the brain and all the other endocrine glands in the body.
An abnormal growth of cells in the pituitary gland is called a pituitary tumor and may create problems because of its location and size.
Pituitary tumors cause:
the pituitary gland to make too many or too few hormones
damage to normal tissue around the pituitary
vision loss if it pushes on the nearby optic nerve
abnormal eye movement if it pushes on nerves in the cavernous sinus
no symptoms at all
Pituitary tumors can occur at any age, but they are more common in older adults. Having a family history of the disease called multiple endocrine neoplasia type 1 (MEN1) can increase the risk of pituitary tumors.
Types of Pituitary Tumors
Pituitary tumors can causes symptoms if the secrete or under-secrete hormones, or if they cause compressive damage to nearby structures. Thus, they can be described as functioning, non-functioning, macro, or micro. These type of pituitary tumors tend not to spread to other parts of the body and remain in the pituitary gland or push into nearby tissues. Small tumors (less than 1cm in size) are called microadenomas and rarely cause local damage the pituitary or nearby tissue. Large tumors (larger than 1 cm) are called macroadenomas and may damage normal pituitary tissue and nearby structures such as the optic nerve. Because the pituitary gland controls all the hormonal functions in the body, both small and large tumors may affect these other hormones. Adenomas can be either functioning or nonfunctioning. Functioning tumors make excess hormones, and non-functioning tumors do not make hormones. Symptoms related to functioning tumors are listed under “Types of Functioning Adenomas.” Nonfunctioning tumors usually present with symptoms that relate to the size of the tumor, which can include:
• Headaches or head pain that may be sudden and severe
• Double vision or less peripheral (side) vision
• Signs of hypopituitarism (low energy, loss of appetite, loss of sex drive), if the tumor has compressed the normal pituitary tissue
Since the posterior pituitary controls the body's water balance state, damage to this portion of the pituitary may cause excessive thirst and frequent urination. This condition is called diabetes insipidus and is related to the amount of anti-diuretic hormone that is produced in the posterior pituitary.
Diabetes insipidus is not the same as diabetes mellitus. Diabetes mellitus is a condition of elevated blood sugars which can lead to an increase in thirst and urination. Diabetes insipidus is usually treated by replacing antidiuretic hormone either by an injection, nasal spray, or tablet.
Types of Functioning Adenomas
There are different types of functioning tumors, and each type causes different signs and symptoms depending on the type of hormone secreted. Some of these tumors may also cause symptoms due to their large size (see above).
Adrenocorticotropic hormone-producing tumors cause the adrenal glands to make a hormone called cortisol. An excess of this hormone may force the adrenal glands make too much of a hormone called cortisol leading to Cushing’s disease. Signs and symptoms of excess cortisol are sometimes difficult to differentiate from changes that can occur from obesity:
• Weight gain around the stomach area and upper back
• Round or swollen face
• Stretch marks that are usually wide and purple in color
• Hump on the upper back and excessive fat above the collar bones
• High blood pressure
• High blood sugar
• Muscle weakness
• Thinning of the skin
• Easy bruising
• Abnormal periods and excessive hair growth (in women)
• Osteoporosis and broken bones
Growth hormone-producing tumors (Acromegaly) make too much growth hormone. Signs and symptoms are dependent on the age at which the excess hormone begins:
• Rough facial features, such as enlarged jaw and prominence of forehead
• Enlarged hands and feet
• High blood pressure and heart enlargement
• Excess hair growth
• Excessive sweating
• Respiratory disorders such as sleep apnea
• Enlargement of the tongue and widening of the spaces between the teeth
• Arthritis and joint pains
• Excessive growth (gigantism) in children
Prolactin-producing tumors (Prolactinoma) make too much of the hormone called prolactin. The effects of high prolactin levels can cause low sex hormone levels. Thus, women would have low estrogen levels and men would have low testosterone levels. The effects of these hormone changes causes different effects in men and women:
For women, it may cause irregular menstrual cycles, no menstrual periods or a milky discharge from the breasts
In men it may cause enlarged breasts, erectile dysfunction (ED), impotence, infertility, less body hair, or a loss of interest in sex
In children it may cause a delay in puberty.
Thyroid-stimulating hormone-producing tumors cause the thyroid gland to make too much of the hormone called thyroxine. This condition is called “secondary hyperthyroidism” leading to an overactive thyroid. However, this form of hyperthyroidism is extremely rare compared to other causes of overactive thyroid which are due to "primary hyperthyroidism". Signs and symptoms of excess thyroid hormone can include weight loss, rapid heart rate, irregular heartbeat, nervousness, irritability, frequent bowel movements, and excessive sweating
Other Pituitary Tumors
These other tumors include Rathke cleft cysts, simple cysts, and craniopharyngiomas. Craniopharyngiomas are the second most common type of tumor occurring in this area. They are present since birth that develop next to the pituitary gland and press on the pituitary or the stem that connects the pituitary to the brain. These tumors often cause hormone, vision and nervous system problems. There are many other very uncommon types of tumors that can appear in the area of the pituitary gland, including germinomas, astrocytomas, or other cancers that spread to the pituitary.
Screening and Diagnosis
There is no single blood or imaging test that can diagnose a specific pituitary tumor. Currently doctors depend on patient symptoms, physical exam testing, abnormal blood hormone levels, and imaging tests. These tests may include a:
• Computerized tomography (CT) scan of the brain/pituitary
• Magnetic resonance imaging (MRI) scan of the brain/pituitary
• Visual field test to check peripheral vision
• Bone X-ray of the hand and wrist to measure if bone growth is normal (in children.)
Doctors treat pituitary tumors with surgery, radiation treatment and medicines. Different combinations are necessary depending on the type of tumor. Treatment for pituitary tumors depends on the specific type of tumor, the size, if it has grown into other areas of the brain, or if there is progressive loss of peripheral vision. Doctors also consider age and overall health. Not all tumors need to be treated, such as microadenomas that are not causing symptoms.
Watchful waiting means that the doctor thinks the best treatment is neither active medical nor surgical intervention. This may be an option if the tumor is not causing any symptoms. Doctors may also recommend watchful waiting if you are older or have other health problems. Most likely, you will need regular follow-up tests. It can also be an option if you are younger, along with regular follow-up tests to watch the tumor.
Health Care Team
Even though watchful waiting is an option for some, treatment may be necessary for many patients, especially if the tumor grows and puts pressure on the brain or optic nerves, which can cause serious problems with hormones, nerve tissue, and loss of vision. A team of doctors is usually involved in treating a pituitary tumor. They include:
• A brain surgeon (neurosurgeon)
• A doctor who treats hormone disorders (endocrinologist)
• A doctor who reads medical images (radiologist)
• A doctor who practices radiation therapy (radiation oncologist)
• A doctor who treats eye disorders (ophthalmologist)
Surgery is the most common treatment for pituitary tumors, especially if the tumor is pressing on the optic nerve or making excessive growth hormone or ACTH. There are two types of surgery for removing a pituitary tumor, depending on the type and the size:
• Transsphenoidal hypophysectomy – The doctor removes the tumor through a cut in the nose and sinuses (nasal passages) or the mouth just behind the upper lip. The brain is not affected, and there is no visible scar. If a tumor is too large or has grown into nearby nerves or brain tissue, then it may be difficult to remove with this type of surgery.
• Transcranial hypophysectomy – The doctor removes the tumor through a cut in the scalp and skull. It is easier to remove a larger tumor using this type of surgery.
Radiation treatment uses high-energy rays to destroy tumors. It can be used after surgery or alone if surgery is not an option. It can also be used if a tumor comes back and causes signs and symptoms that medicines do not relieve. Radiation treatment includes:
• External beam radiation – Small amounts of radiation are given every day over four to six weeks, usually on an outpatient basis. Although this treatment is often effective in reducing tumor size, it may take years to see results for a functioning tumor.
• Stereotactic radiosurgery – Small beams of radiation that are the exact size and shape of the tumor are sent into the tumor to destroy it in a single session. Because a small amount of radiation is used, it is less likely to affect the tissue around the tumor. Sometimes the benefits of this treatment do not happen right away. It may take months or years to see results. This type of treatment cannot be used if a tumor is too close to the optic nerve or other nearby nerves and brain tissue.
• Prolactin-producing tumor (prolactinoma) – These can be treated with drugs, such as bromocriptine (Parlodel®) and cabergoline (Dostinex®), to lower the amount of prolactin. This often reduces the size of the tumor. These drugs usually work so well that patients do not need surgery.
• Growth hormone-producing tumors – These can be treated with drugs called somatostatin analog (Sandostatin®, Somataline®) to lower the amount of growth hormone produced and may make the tumor smaller. The other drug is pegvisomant (Somavert®) which blocks the end-organ receptors from the effects of excess growth hormone. These medicines are often used when surgery does not result in a cure. If the tumor or removal of the tumor lowers your hormones, then you may need to take hormone replacement therapy.
After the pituitary tumor has been treated, it will still be necessary for you to see specific specialists:
• An endocrinologist to test your hormone levels checked regularly and to decide when an MRI of the pituitary may be needed.
• An ophthalmologist for regular vision tests
• A neurosurgeon for further surgery in case the tumor has come back.
• How often these tests are done will depend on the type of tumor and your medical history.