How common are these tumors?
Pituitary tumors and pituitary adenomas (small tumors) are common. In autopsy studies of patients who did not have known pituitary disease, as many as 26% had a small pituitary tumor.
What causes a pituitary tumor?
Molecular biology studies have shown that a change in the DNA (genetic mutation) of a pituitary cell can cause unregulated growth of that cell resulting in a pituitary tumor, called an adenoma.
There are no known environmental causes.
One very uncommon type of pituitary tumor, multiple endocrine neoplasia type I, is inherited. In this situation, there is usually a family history of endocrine tumors, most commonly a parathyroid tumor causing high blood calcium levels, a pituitary tumor which may or may not produce an excessive amount of a hormone or, less commonly, a neuroendocrine tumor of the pancreas. This happens in fewer than 4% of patients with a pituitary tumor.
Is a pituitary tumor a brain tumor?
No. The pituitary gland is not in the brain and pituitary tissue is different from brain tissue.
The pituitary gland is located at the base of the brain and is connected to the brain by a thin stalk.
Because the pituitary gland is close to the brain, it's easy to confuse these tumors with brain tumors. Insurance companies sometimes classify pituitary tumors incorrectly.
What are the symptoms of a pituitary tumor?
This depends on the type and size of the tumor.
A large tumor may cause vision loss, particularly peripheral vision, if it compresses the optic chiasm (where the optic nerves of the eyes come together, located above the pituitary gland).
Tumors of all sizes can cause headaches. The type of headache varies from person to person.
A tumor may interfere with normal pituitary function causing:
- Hypothyroidism (low thyroid hormone level)
- Adrenal insufficiency (low cortisol level)
- Hypogonadism (loss of sexual function and fertility in men, loss of menstrual periods or fertility problems in women)
Sometimes, a pituitary tumor causes diabetes insipidus, which causes frequent urination and excessive thirst. Diabetes insipidus is not high blood sugar; it's is a problem with the kidneys' ability to retain fluid because you don't have enough vasopressin (also called antidieuretic hormone) to regulate water balance.
Read more about pituitary tumor symptoms.
How is a pituitary tumor diagnosed?
We diagnose with:
In some cases, a pituitary tumor is found when a provider orders an MRI for a patient with headaches, trauma, or vision loss. This requires a full endocrine (hormone) evaluation and eye examination. The endocrine evaluation determines if you have too much or too little of any hormones.
The evaluation includes tests for:
- Adrenal cortisol production (cortisol and ACTH)
- Thyroid function (free T4 and TSH)
- Growth hormone production (IGF-1 level)
- Gonadal function (men: testosterone and LH levels; premenopausal women: menstrual history, LH, and estrogen levels)
- Prolactin level
We'll also ask about frequent urination.
If we suspect Cushing’s, you may need a 24 hour urine test to see if you're producing too much cortisol.
In the case of a large tumor that is near or pressing on the optic chiasm (nerves responsible for vision), a thorough eye examination, including visual acuity and visual field examination, is needed.
What's the best treatment?
It depends on the tumor. Read more about pituitary tumor treatment.
If my pituitary tumor is removed successfully, why do I need follow-up?
Pituitary tumors come back in a small percentage of patients. You may need bloodwork or MRIs to check for tumor recurrence.
Do all pituitary tumors need radiation?
Radiation is not the first line of treatment for most pituitary tumors. It does not produce an immediate effect to lower excessive hormone production or shrink the tumor.
Radiation is used when there is tumor remaining after surgery or when surgery is cannot be performed. Pituitary radiation may take several years to be effective. For example, in patients with acromegaly (excessive growth hormone production), growth hormone levels may remain elevated for 10 to 20 years after conventional (fractionated) radiation.
What kind of radiation is used?
There are different ways to deliver radiation to the pituitary gland. Conventional (fractionated) radiation refers to delivery of a small amount of radiation every day for 4 to 5 weeks. Stereotactic radiation refers to delivery of a precisely focused beam of radiation to the remaining tumor, usually as one or a few treatments (Gamma Knife, LINEAC, Cyber knife, proton beam).
We determine which type of radiation to use by carefully reviewing your MRI to assess the size and location of residual tumor.
Stereotactic radiation is only appropriate for a small tumor that is not near the optic chiasm.
Does radiation cause side effects?
The most common side effect is loss of normal pituitary function. This may happen within a year or many years after treatment.
One study reported that 50% of patients treated with conventional radiation developed deficiency of one or more pituitary hormones within 2 years of treatment.
Studies of Gamma Knife suggest that about one-third of patients develop a pituitary hormone deficiency 2 to 3 years after treatment.
If you develop pituitary hormone deficiency, we can treat it with hormone replacement therapy.
An uncommon side effect is damage to vision. These risks must be weighed against the risk of tumor regrowth.
Most patients don't lose their hair.
Can a pituitary tumor shorten your life?
A pituitary tumor usually doesn't shorten life expectancy if treated properly.
If your tumor causes hormone deficiency, it's important to take your medication as directed.
It's also important to wear a medical alert bracelet if you need steroid (cortisol) replacement. If you have another illness or accident, you may need additional steroid. The bracelet will alert medical providers if you're not able to tell them your medical history.
In large population studies, patients who had conventional, fractionated radiation for pituitary disease had an increased risk of death from stroke.
Patients with uncontrolled acromegaly (growth hormone producing tumor) or Cushing’s disease (excessive cortisol production) do have an increased risk of early death and complications from high hormone levels. Lowering hormone levels to normal reduces this risk.