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Pituitary Microadenoma

What is a pituitary microadenoma?

A pituitary microadenoma is a benign tumor of the pituitary gland with a diameter less than 10 mm (those with a diameter greater than 10 mm are called pituitary macroadenomas).

diagram showing a pituitary microadenoma tumor growing on the pituitary gland
An illustration showing a microadenoma growing on the pituitary gland. In this diagram, the brain is above the pituitary tumor and gland, and the nose and sinuses are below and to the right.

Pituitary Microadenoma Symptoms

Most microadenomas do not cause symptoms and do not require treatment. However, some microadenomas cause symptoms by secreting hormones that harm your body, for example, in Cushing’s disease, acromegaly, and hyperprolactinemia.

Symptoms of a pituitary microadenoma may include the following:

  • Tiredness
  • Headaches
  • Vomiting
  • Dizziness
  • Vision problems
  • Nausea
  • Menstrual or breast changes
  • Unexplained hair growth or loss

Pituitary Microadenoma Treatments


For prolactin-secreting microadenomas, most patients will choose to take medication to shrink their tumor and block the hormone effects in the body.  For microadenomas that cause Cushing’s disease and acromegaly, surgery is the preferred treatment because it is more effective than medication.


Surgery is the best form of treatment and the only way to achieve a cure. Your surgeon will gain access to your pituitary gland using the transsphenoidal approach—so named because the route your surgeon takes uses the sphenoid sinus. This natural openings in your body can be used by surgeons to make the surgery less invasive. This bone is located behind your nose, mostly within your skull.

Using precise surgical instruments, your surgeon will enter your nasal cavity and create an opening in your sphenoid bone. At Barrow, our surgeons do not make any external incisions on your face, and you will not have any bruising. Once your surgeon gains access to your sphenoid sinus (the air-filled area behind the sphenoid bone), further openings will be made until a hole is created in the sella turcica—the bone that cradles and protects your pituitary gland.

Once your tumor appears in the operative field, removal of the tumor can proceed. Your surgeon will use high magnification to help distinguish normal pituitary tissue from the tumor.

After the tumor has been removed, your surgeon will clean the tumor cavity and seal it off. At Barrow, our surgeons specialize in endoscopic pituitary surgery. Endoscopic pituitary surgery uses a tiny camera to enter the nostrils to remove the tumor.

The surgery aims to minimize trauma to the tissue surrounding your pituitary gland while facilitating a speedy recovery with as little pain or discomfort as is possible.

Most patients are able to return home the day after their surgery.


Gamma Knife radiosurgery is a highly advanced form of accurate radiation that is used to achieve similar results to the traditional surgical techniques described above. However, with Gamma Knife it can take several years for elevated hormone levels to return to normal, rather than days or weeks as with traditional surgery.

The ‘knife’ in this surgery is actually made up of many small beams of radiation focused on a single point. Each individual beam is too weak to damage healthy tissue, but at the point where the beams converge they deliver a dose of radiation that is lethal to the tumor.

Gamma Knife is an outpatient procedure, does not involve any incisions, and requires only brief sedation under general anesthetic.

Additional Information

How common are pituitary microadenomas?

Pituitary microadenomas can occur in either sex. As many as 10 percent of the population may have a microadenoma, but most do not cause symptoms. Prolactinomas, a subset of microadenomas, are diagnosed more frequently in women, possibly because of the more striking presenting features such as amenorrhea, galactorrhea, or both.

In men, the diagnosis of inactive adenomas often occurs later in life until they have become macroadenomas and cause symptoms by compressing nearby structures. Microadenomas can occur at any age, but prevalence appears to increase with age.

How are pituitary microadenomas diagnosed?

A pituitary microadenoma can be diagnosed through a variety of tests. Your doctor may suspect you have a microadenoma if you have the symptoms listed above. Possible tests to confirm this diagnosis include the following:

  • Blood tests
  • Urine tests
  • Visual field tests
  • Computed tomography (CT)
  • Magnetic resonance imaging (MRI)
  • Inferior petrosal sinus sampling (IPSS)

Is a pituitary microadenoma tumor curable?

In most cases, a microadenoma can be cured with endoscopic transsphenoidal surgery. In this procedure, a neurosurgeon reaches the tumor through the nasal passages and sphenoid sinus.

Gamma Knife radiosurgery, which uses targeted beams of radiation to destroy the tumor, is another option. However, with GammaKnife it can several years for elevated hormone levels to return to normal, rather than days or weeks with surgery. Gamma Knife, or other types of radiation treatment, are usually used if surgery or medication do not seem to be working.

Is a pituitary microadenoma cancerous?

A pituitary microadenoma is almost always noncancerous, meaning it does not spread to other parts of the body.

Can a microadenoma cause weight gain?

Yes, a microadenoma can cause weight gain. This depends on how the tumor affects the pituitary gland and the function of the tumor itself.

Group 49
As many as 10 percent of the population may have a microadenoma, but most do not cause symptoms.
Medically Reviewed by Andrew S. Little, MD, FAANS, FACS and Kevin C.J. Yuen, MBChB, MD, FRCP, FACE on October 8, 2021