Condition Pituitary Tumors

Pituitary Adenoma

Usually benign tumors of the pituitary gland that can affect hormone production, vision, and nearby structures — with treatment guided by the tumor type, hormone activity, size, and location.

Medically reviewed by Yaron A. Moshel, MD, PhD Last reviewed August 5, 2026 9 min read

Quick Answer

A pituitary adenoma — also classified as a pituitary neuroendocrine tumor, or PitNET — is a usually benign growth of the pituitary gland. These tumors can cause problems by producing too much of a particular hormone or by growing large enough to press on the normal gland, optic nerves, or nearby structures. The tumor’s hormone activity and cell lineage help guide treatment: some tumors, especially prolactin-producing tumors, are often treated effectively with medication, while others are more likely to require surgery. Many small tumors found incidentally need only monitoring. When surgery is needed, most pituitary tumors can be removed through the nose using an endoscopic endonasal approach, without opening the skull or retracting the brain.

Key Takeaways

Pituitary adenomas are usually benign tumors of the pituitary gland and are also classified as pituitary neuroendocrine tumors (PitNETs).
Symptoms may come from excess hormone production, pressure on the optic nerves or nearby structures, or reduced function of the normal pituitary gland.
Modern classification considers the pituitary cell lineage the tumor arose from, which can provide important information about behavior and treatment response.
Not every pituitary adenoma requires surgery — prolactin-producing tumors in particular are often treated first with medication.
When surgery is needed, most pituitary tumors can be approached endoscopically through the nose without a traditional craniotomy.
Care often involves neurosurgery, endocrinology, ophthalmology, and skull base ENT, with hormone and imaging follow-up continuing after treatment.
Atlantic Brain and Spine’s skull base team has been designated a Multidisciplinary Team of Distinction by the North American Skull Base Society.

At a Glance

Condition type	Usually benign tumor of the pituitary gland
Also called	Pituitary neuroendocrine tumor (PitNET)
Location	Pituitary gland at the base of the brain, within the sella turcica
Types	Functioning or nonfunctioning, with further classification by pituitary cell lineage
How common	Among the more common primary intracranial tumors; small pituitary lesions are also frequently found incidentally
Common symptoms	Hormonal changes, headaches, fatigue, or loss of peripheral vision
Diagnosis	Dedicated pituitary MRI, hormone testing, and formal visual field testing when indicated
Treatment	Observation, medication, surgery, or stereotactic radiosurgery depending on tumor type and effects
Common surgery	Endoscopic endonasal transsphenoidal surgery through the nose
Surgical team	Neurosurgery and skull base ENT working together, with endocrinology and ophthalmology involved in multidisciplinary care

What Is a Pituitary Adenoma?

A pituitary adenoma is a tumor that develops from the hormone-producing cells of the pituitary gland, a structure about the size of a pea that sits in a bony hollow at the base of the brain, directly beneath the optic nerves. Because the pituitary helps regulate many of the body’s hormones, even a relatively small tumor can have significant effects.

These tumors are overwhelmingly benign and do not behave like typical cancers. Some grow into neighboring structures such as the cavernous sinus, which can make complete removal more difficult but does not by itself make the tumor malignant.

The current World Health Organization classification uses the term pituitary neuroendocrine tumor (PitNET), although pituitary adenoma remains widely used by physicians and patients. The newer terminology reflects changes in how these tumors are classified rather than a change in how they behave.

Pituitary tumors can cause problems in two main ways: by producing too much of a particular hormone or by growing large enough to compress the normal pituitary gland, optic nerves, or other nearby structures. A larger tumor can also reduce normal hormone production by compressing healthy pituitary tissue.

Some pituitary adenomas are discovered incidentally on an MRI performed for another reason and may never require treatment. Even when a tumor is found by chance, hormone evaluation is important, and formal vision testing may be recommended if it approaches the optic nerves.

Types of Pituitary Adenomas

Pituitary tumors are described by whether they produce excess hormone, how large they are, and which pituitary cell lineage they arose from. Modern pathology uses cell-lineage information to refine the diagnosis and provide information about how a tumor may behave or respond to treatment.

Prolactin-Producing

Lactotroph tumors produce prolactin and cause prolactinoma. They are the most common functioning pituitary tumors and are usually treated first with medication rather than surgery.

Growth Hormone-Producing

Somatotroph tumors can cause acromegaly, with gradual enlargement of the hands, feet, and facial features as well as other metabolic effects.

ACTH-Producing

Corticotroph tumors can cause Cushing disease, including weight gain concentrated in the trunk and face, easy bruising, high blood pressure, and muscle weakness.

TSH-Producing

Thyrotroph tumors are rare and produce thyroid-stimulating hormone, which can cause hyperthyroidism and may initially resemble a primary thyroid disorder.

Nonfunctioning

These tumors do not produce enough hormone to cause a recognizable excess-hormone syndrome. Many are gonadotroph tumors and are discovered only after they become large enough to affect vision, cause headaches, or reduce normal pituitary function.

Size still matters: A microadenoma measures less than 1 centimeter, while a macroadenoma measures 1 centimeter or larger. Size helps describe the tumor, but hormone activity, location, cell lineage, and relationship to nearby structures are also important in deciding what treatment is appropriate.

Within these categories, pathologists may identify additional subtypes that behave differently from what size or hormone production alone might suggest. These details can help explain why some tumors respond differently to medication or require closer long-term follow-up.

Signs & Symptoms

Symptoms generally come from one of three sources: excess hormone production, pressure on nearby structures, or reduced function of the normal pituitary gland. Many patients have symptoms from more than one category.

Hormone Excess

Symptoms depend on which hormone is involved and may include menstrual changes, milk production unrelated to nursing, low libido, infertility, enlargement of the hands or feet, weight changes, easy bruising, high blood pressure, or muscle weakness.

Pressure on Nearby Structures

A tumor growing upward can compress the optic nerves and cause loss of peripheral vision, often before central vision changes. Headaches are common, and extension into the cavernous sinus can sometimes affect eye movement and cause double vision.

Reduced Pituitary Function

Compression of the normal gland can lower hormone production and cause fatigue, low energy, cold intolerance, low libido, menstrual changes, or other symptoms that may be mistaken for more common problems.

Hormonal changes often develop gradually, which is one reason pituitary tumors can go unrecognized for years. Vision loss can also be subtle: patients may notice bumping into door frames or missing a car in the next lane before realizing their peripheral vision has changed.

Pituitary apoplexy is an emergency. Rarely, a pituitary tumor can bleed or suddenly lose its blood supply, causing an abrupt severe headache, rapid vision change, double vision, confusion, collapse, or other serious symptoms. Immediate medical evaluation is required.

Common Signs & Symptoms

Loss of side or peripheral vision
Persistent or worsening headaches
Unexplained changes in weight or body composition
Menstrual changes, fertility problems, or sexual dysfunction
Fatigue, weakness, or low energy

Pituitary Apoplexy: Emergency Signs

Sudden, severe headache
Sudden vision loss or rapid vision change
New double vision
Confusion, fainting, or collapse
Severe weakness or vomiting

Diagnosis

Diagnosing a pituitary adenoma requires more than identifying a mass on a scan. The evaluation brings together imaging, hormone testing, and vision assessment to determine what type of tumor is present and what effects it is having.

Pituitary MRI

MRI with dedicated pituitary views defines the tumor’s size, location, and relationship to the optic nerves, cavernous sinus, normal gland, and other nearby structures.

Hormone Testing

Testing evaluates the major pituitary hormone systems for both excess production and deficiency. Some hormone disorders require specialized testing rather than a single random blood level.

Formal Visual Fields

When a tumor approaches the optic nerves, formal visual field testing maps peripheral vision. This can detect the characteristic pattern of loss even when a standard eye chart remains normal.

The combination of imaging, hormone results, vision testing, and pathology when tissue is available defines the tumor and its effects. Together, those findings guide whether the best approach is observation, medication, surgery, radiation, or a combination of treatments.

Treatment

Treatment depends on the specific diagnosis, tumor size and location, hormone activity, effects on vision, and involvement of nearby structures.

Observation

Not every pituitary tumor needs immediate treatment. A small, nonfunctioning tumor that is not affecting hormone levels or vision can often be followed with periodic MRI and hormone testing. If it remains stable, follow-up intervals may become longer over time.

Medication

Prolactin-producing tumors are usually treated first with medication. Dopamine agonists can lower prolactin levels and shrink many of these tumors, sometimes enough to relieve pressure on the optic nerves without an operation. Surgery may be considered when medication is not effective, is not tolerated, or when another urgent indication is present. For some other hormone-producing tumors, medication may be used after surgery when hormone levels remain elevated.

Endoscopic Pituitary Surgery

For many pituitary tumors that require surgery — including tumors causing vision loss and many growth hormone- or ACTH-producing tumors — the operation is performed endoscopically through the nose. There is no external incision and no need to retract the brain.

A high-definition endoscope provides a wide view of the pituitary region and can help the surgical team see tumor extending toward the optic nerves or cavernous sinus. Larger tumors extending above the gland can often be addressed through expanded versions of the same endonasal approach.

For tumors causing visual loss, timely decompression of the optic nerves can be important. For hormone-producing tumors, success is measured not only by how much tumor is removed but also by whether hormone levels return to an appropriate range.

When radiation is considered: Stereotactic radiosurgery or other focused radiation may be used for selected residual or recurrent tumors, particularly when additional surgery is not the best option. The decision is individualized based on tumor type, location, prior treatment, hormone activity, and proximity to the optic nerves.

Multidisciplinary Pituitary Care

Why the Team Matters

Pituitary surgery is performed by a neurosurgeon and a skull base ENT surgeon working together through the endoscopic nasal corridor. Endocrinology, ophthalmology, neuroradiology, and radiation oncology are involved as needed before and after treatment.

Recognized Skull Base Team

Atlantic Brain and Spine’s Skull Base Surgery Center has been designated a Multidisciplinary Team of Distinction by the North American Skull Base Society, recognizing an established multidisciplinary approach to skull base care.

The Diagnosis-to-Treatment Pathway

1. Evaluation

History and neurological examination identify hormone-related symptoms, headaches, and possible vision changes.

2. Pituitary MRI

Dedicated imaging defines the tumor’s size, location, and relationship to the optic nerves and surrounding structures.

3. Hormone testing

Laboratory testing checks for both excess hormone production and reduced pituitary function.

4. Vision assessment

Formal visual field testing measures peripheral vision when the tumor approaches or compresses the optic nerves.

5. Define the tumor type

Hormone activity, imaging, and pathology when available help determine whether observation, medication, or surgery is most appropriate.

6. Treatment

Prolactinomas are often treated medically; tumors affecting vision or causing other hormone syndromes may require endoscopic surgery.

7. Additional therapy if needed

Focused radiation or additional medical therapy may be considered for selected residual, recurrent, or persistent disease.

8. Long-term follow-up

MRI, hormone testing, and vision monitoring continue after treatment based on the tumor type and response.

Frequently Asked Questions

The great majority of pituitary adenomas are benign, not cancer. They can still cause important problems by producing excess hormones, reducing normal pituitary function, or pressing on nearby structures such as the optic nerves.

Yes. Some small tumors need only monitoring, and prolactin-producing tumors are usually treated first with medication that can lower hormone levels and shrink the tumor. The best approach depends on the tumor type and its effects.

The pituitary gland sits directly below the optic nerves. A tumor that grows upward can compress them, often causing loss of side or peripheral vision before central vision is affected.

It is removal of the tumor through the nostrils using an endoscope. There is no external incision and no brain retraction. The surgical team reaches the pituitary through the natural nasal and sinus corridor.

It depends on the tumor and how well the normal pituitary gland is functioning. Some tumors are treated with hormone-related medication, and some patients need hormone replacement if normal pituitary function is reduced. Endocrinology follow-up is an important part of care.

Some can recur or regrow, particularly when tumor remains after treatment. Follow-up may include MRI, hormone testing, and vision assessment so that changes can be identified and treated appropriately.

Pituitary apoplexy is sudden bleeding into a pituitary tumor or loss of its blood supply. It can cause a severe abrupt headache, rapid vision changes, double vision, confusion, collapse, or hormone problems and requires emergency medical evaluation.

Specialists Who Treat Pituitary and Parasellar Tumors

Pituitary tumor care at Atlantic Brain and Spine brings together neurosurgery, skull base ENT, endocrinology, ophthalmology, neuroradiology, and radiation oncology as needed for each patient.