Treating pituitary tumors

Once you have identified that a patient has a pituitary tumor, it’s important to know how to manage the patient’s treatment. Treatment approaches differ depending on whether the tumor is secreting hormones or not, and which hormones are affected.

Patients with small, non-secreting tumors can be monitored without treatment. These tumors will often remain unchanged in size over several decades, and patients will typically remain asymptomatic.

With the advent of modern imaging, patients with non-secreting pituitary tumors can be easily followed, and minimal increases in size will be caught. To follow a newly discovered, small, non-secreting tumor, repeat magnetic resonance imaging (MRI) after 6 months and then annually, watching for tumor growth.

If the tumor does enlarge, consult neurosurgery. The only time that a small non-secreting pituitary tumor needs to be addressed surgically is if it has shown definitive growth.

Prolactin-secreting tumors (even large ones) are initially treated with dopamine agonists such as bromocriptine or cabergoline. Generally, these medications will effectively lower prolactin levels and halt tumor growth.

During treatment of a prolactin-secreting pituitary tumor, monitor prolactin levels every 3–4 months for treatment response. Usually, the initial response will involve a dramatic drop in serum prolactin within a few days. An increase in prolactin at any time may indicate tumor progression.

Prolactin-secreting tumors sometimes respond so well to dopamine agonists that they actually begin to shrink and can completely involute! If prolactin values come down to normal, continue treatment for 2–4 years and then consider gradually discontinuing the medication.

After dopamine agonists are discontinued, obtain prolactin levels every 3–4 months, and repeat the MRI at 6 and 18 months. If there is no further tumor growth at this point, and prolactin levels remain normal, the follow-up appointments can be lengthened to every two years. Sometimes (but not always) this medical regimen seems to be curative.

Surgery should be performed for prolactin-secreting tumors if the medication fails to respond or is poorly tolerated. Some patients have significant side effects with dopamine agonists such as dizziness, headaches, nausea, vomiting, and other gastrointestinal complaints.

Surgery

For large non-secreting tumors (particularly those compressing the optic apparatus), and for all other hormone-secreting tumors, surgery is the primary treatment. This is particularly true of growth hormone-, thyrotropin-, and corticotropin-secreting tumors. Large tumors can compress critical structures such as the optic chiasm, and hormone-secreting tumors can cause major metabolic and physiological derangements.

Surgery is generally performed through the nose. To best understand this approach, simply look at a midline sagittal MRI scan. There is a direct route through the nose and into the sphenoid sinus. The sella turcica, and therefore the pituitary gland, lies in the roof of the sphenoid sinus.

The surgery is generally performed using an operating microscope or endoscope. Often, otolaryngologists and neurosurgeons will perform the surgery together. This surgery is relatively safe and straightforward in the hands of an experienced neurosurgeon. Post-surgery hospitalization is generally just a few days to assure hormonal stability.

Stereotactic radiation

Stereotactic radiation has been used on some recalcitrant tumors (e.g., cannot be completely removed surgically), but it carries a risk of panhypopituitarism and optic chiasm injury. Recurrent tumors have sometimes been treated with stereotactic radiation, particularly if re-do surgery has been performed (but there is a significant residual tumor).

Abnormal hormone levels

After a pituitary tumor resection, ask the patient about urinary frequency and fluid ingestion. Frequent urination and increased fluid intake can be signs of diabetes insipidus caused by a deficiency in an antidiuretic hormone. These patients may urinate in tremendous volumes each day. If they are fully cognizant and can manage their oral intake well, they will compensate by drinking a lot of fluids. Nonetheless, this can result in significant electrolyte abnormalities.

Temporary diabetes insipidus is not uncommon after surgery and often resolves spontaneously. However, it can sometimes become a long-term problem. Generally, persistent diabetes insipidus should be treated with an antidiuretic hormone (ADH) analog such as desmopressin.

Consider prescribing desmopressin if the urinary frequency and the drive to drink fluids persists and reaches the nuisance level, such as causing the patient to be up multiple times at night to urinate.

If not done by the neurosurgery or endocrinology teams, obtain a full battery of pituitary hormone levels 1–3 months postoperatively. Make sure to keep the patient involved with endocrinology specialists.

Although it is uncommon, be alert for signs of hypoadrenalism. Untreated hypoadrenalism can result in multisystem collapse and death. If you are unsure whether the patient is experiencing hypoadrenalism, it’s best to consult an endocrinologist.

Spinal fluid leakage

Spinal fluid leakage is not uncommon after pituitary surgery, particularly for macroadenomas. Be on the look-out for a spinal fluid leak. This appears as persistent clear discharge from the nose—particularly if the patient is leaning forward.

Sometimes, spinal fluid leakage can feel like a constant postnasal drip or a recurrent salty taste in the mouth. Imaging may not help to diagnose this issue. If the clear fluid can be collected, it can be tested for beta-2 transferrin, which would secure the diagnosis. If you suspect a spinal fluid leak, get the patient back to their surgeon.

Order a contrast MRI 3–4 months after surgery to assess the tumor resection. MRI earlier than this is messy due to the detritus of surgery, and the findings are often inconclusive. Follow-up MRI and hormonal testing should be obtained 1 year postoperatively and every 1–2 years afterward if the patient is stable.

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