The pituitary gland is a major hormone control center that sits just below the hypothalamus and is connected to the hypothalamus by a stalk. The optic nerves and optic chiasm sit between the pituitary and the hypothalamus.
Notably, the pituitary gland is somewhat prone to tumor formation. Pituitary tumors are usually benign, although metastases do rarely occur in the pituitary region.
What is the pattern of disease seen in pituitary tumors?
Signs and symptoms
Pituitary tumors arise from tissues that produce hormones—so the tumors can be hormonally active. As a result, many pituitary tumors (even very small ones) can cause profound hormonal derangement by hyperproduction of pituitary hormones.
Some hormones are quite harmful when overproduced and can lead to illness and death. These include adrenocorticotropic hormone or corticotropin (ACTH), thyroid-stimulating hormone or thyrotropin (TSH), and growth hormone.
But, many pituitary tumors are not hormonally active. These are known as non-secreting tumors. However, non-secreting tumors can still cause problems by altering normal hormonal production or compressing nearby structures.
Pituitary tumors can grow to be quite large. Large tumors can shut down the normal production of pituitary hormones by squeezing the gland, causing panhypopituitarism (although this is not common).
Pituitary tumors can also extend out of the sella turcica (the bony region at the base of the skull surrounding the pituitary gland) and into the region above which compresses nervous tissue in the area. Large tumors frequently compress the optic nerves, optic tracts, or the optic chiasm.
Pituitary tumors can cause gradual vision loss in one eye, both eyes, both temporal visual fields (known as bitemporal hemianopsia), or two symmetric half-fields (known as homonymous hemianopsia). With time, the tumors may result in total blindness.
Large pituitary tumors can also extend laterally into the cavernous sinus, where they can cause dysfunction in the cranial nerves responsible for eye movement. Very large tumors can compress vital brain regions, block cerebrospinal fluid (CSF) pathways, and cause hydrocephalus.
Sudden onset of severe headache and diminished vision may signify hemorrhagic infarction in a pituitary tumor, which causes a rapid expansion of the tumor and subsequent optic chiasm compression. This constitutes a surgical emergency—particularly if visual loss is severe. With these symptoms, consult neurosurgery right away. This condition is known as pituitary apoplexy.
What to do if you suspect a pituitary tumor?
The presence of a pituitary tumor is generally established by magnetic resonance imaging (MRI). After determining that a patient has a tumor, the goal is to find out how it is affecting the patient.
Obtain a general medical history
When evaluating a patient with a newly discovered pituitary mass, obtain a general medical history to identify headaches, visual changes, and symptoms of hypo- or hyperproduction of various pituitary hormones.
Inquire about amenorrhea (the absence of menstruation), galactorrhea (excessive or inappropriate production of breast milk), or impotence; these are classic signs of prolactin hypersecretion. Prolactin-secreting tumors (e.g., prolactinomas) are the most common hormone-secreting pituitary tumor.
Ask the patient about enlargement of their hands, fingers, or feet, and a coarsening of facial features. These are symptoms commonly seen with growth hormone hypersecretion (a condition known as acromegaly).
Heat intolerance, tremor, nervousness or agitation, rapid heart rate, palpitations, and an irregular heartbeat are common signs of increased thyrotropin secretion (a condition known as central hyperthyroidism).
Weight gain, rounding of the face, increased fat around the base of the neck and between the shoulders, easy bruising, and purple stretch marks on the abdomen and breasts are common signs of increased secretion of corticotropin. This is known as Cushing’s disease.
Growth hormone deficiency is associated with centripetal obesity, reduced exercise tolerance, and decreased lean body mass.
Cold intolerance, unexplained weight gain, entrapment neuropathies, and myxedema may signal hypothyroidism.
As well, orthostatic hypotension, easy fatigability, and confusion can result from hypoadrenalism.
Perform a neurological exam
When evaluating a patient with a pituitary mass, perform a neurological exam that focuses on visual acuity, visual fields, and eye movement.
The most common visual field loss is bitemporal hemianopsia, which results from direct compression of the optic chiasm. Remember that if the tumor does not extend out of the sella turcica, it will not cause visual deficits.
Obtain diagnostic imaging
Next, review the patient’s MRI scans. Most tumors will be obvious masses that readily brighten up (e.g., enhance) on contrast T1-weighted MRI scans. Make sure to look at the mass in coronal and sagittal sections since they are easier to appreciate in these views (in comparison to axial images).
Note the degree of extension out of the sella turcica and the degree of compression of the optic chiasm. Keep in mind that these tumors can also extend inferiorly into the sphenoid sinus, but they create little trouble in that area.
Small tumors known as microadenomas can still cause overproduction of pituitary hormones, but can be difficult to see on imaging studies. Review MRI of suspected pituitary tumors with a neuroradiologist if you do not see an obvious tumor.
Perform additional testing
If you suspect a pituitary tumor, perform a standard pituitary battery of blood tests to look for variations in hormone levels:
- 8:00 a.m. serum cortisol
- 24-hour urine free cortisol
- Serum free thyroxine and thryoid-stimulating hormone (TSH)
- Serum prolactin
- Serum follicle-stimulating hormone (FSH)
- Serum luteinizing hormone (LH)
- Estradiol in women
- Testosterone in men
- Insulin-like growth factor 1 (IGF-1)
- Fasting blood glucose
- Urine specific gravity and osmolarity (arginine vasopressin deficiency)
More complex cases of hormonal derangement may need in-depth endocrinology testing before and after pituitary surgery. Likewise, complex radiological evaluations (angiography with venous sinus sampling) may be necessary when laboratory evaluations point to a likely tumor. But, radiographic evaluations of the pituitary gland are equivocal.
Refer to specialists for evaluation
All patients with definitive pituitary tumors should undergo endocrinology and neurosurgery evaluations and follow ups. Patients with visual deficits or compression of the optic apparatus should undergo a formal neuro-ophthalmological evaluation and formal visual field testing as well.
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- American Association of Neurological Surgeons. 2020. Pituitary gland and pituitary tumors. American Association of Neurological Surgeons. https://www.aans.org
- Laws, ER, Ezzat, S, Asa, SL, et al. 2013. Pituitary Disorders: Diagnosis and Management. 1st edition. New Jersey: Wiley-Blackwell.
- Mulinda, JR. 2020. Pituitary macroadenomas. Medscape. https://emedicine.medscape.com/