Pituitary Adenomas

Pituitary adenomas are the third most common intracranial tumor and arise from the pituitary gland.

Pituitary adenoma surgery is necessary for the great majority of symptomatic pituitary adenomas. Transsphenoidal surgical removal (via the nose) is typically the treatment of choice. Fortunately, pituitary adenoma surgery has had major technical advances over the last 15 years, including use of high-definition endoscopy, surgical navigation techniques and more effective skull base closure methods. At Saint John’s Pituitary Disorders Program, we have one of the world’s largest experiences in endonasal endoscopic transsphenoidal surgery for all types of pituitary adenomas including acromegaly, Cushing’s disease, prolactinomas, non-functional adenomas, pituitary apoplexy and residual or recurrent adenomas.  By incorporating cutting edge technology and instrumentation with proven surgical experience of over 1600 endonasal surgeries, our pituitary tumor specialsts make pituitary surgery safer, less invasive and more effective.

For tumors such as prolactinomas that are often best treated with medical therapy, we have highly experienced endocrinologists to provide this therapy. For patients with adenomas that cannot be completely treated with surgery and/or medical therapy, our outstanding radiation oncologists can deliver focused radiosurgery or radiotherapy to tumors, halting their growth. We also have clinical trials available using novel medical therapies for patients with persistent acromegaly and Cushing’s disease who failed prior treatments. 

Learn more about our multidisciplinary team of Neurosurgery, Endocrinology, Otolaryngology, Radiation Oncology, Neuro-Ophthalmology and Neuro-Oncology.


Pituitary adenomas arise from the pituitary gland and are by far the most common growth associated with the gland; they account for 15-20% of primary brain tumors and are the third most common intracranial tumor after Gliomas and Meningiomas. The great majority (over 90%) of pituitary adenomas are benign slow growing tumors, approximately 5-10% are somewhat more aggressive (atypical) and less than 1% qualify as pituitary carcinoma. From autopsy studies and MRIs of normal individuals, it is known that 10-20% of the general population has a pituitary adenoma. Most of these tumors remain small and do not cause significant harm or symptoms. However many do progress and grow to cause major hormonal and neurological problems. Adenomas are classified by size and whether they produce pituitary hormones; microadenomas are less than 1 cm in diameter and macroadenomas are over 1 cm in diameter. Adenomas that make excess hormones (endocrine-active adenomas) include prolactin-secreting adenomas known as Prolactinomas, adrenocorticotropic hormone (ACTH) secreting adenomas causing Cushing’s Disease, growth hormone (GH) secreting adenomas causing Acromegaly, and thyroid stimulating hormone (TSH) secreting adenomas causing hyperthyroidism. Adenomas that do not make excess hormones are called Endocrine-Inactive or Non-Functional Adenomas. Most adenomas are not genetically inherited; cases of familial pituitary tumors are rare. Multiple Endocrine Neoplasia (MEN) type I accounts for less than 5% of cases of pituitary adenomas. This autosomal dominant condition is characterized by multiple and sometimes simultaneous tumors of the pituitary, pancreas and parathyroid glands. Pituitary adenomas develop in 25% of patients with MEN I.


Pituitary adenomas may cause problems because of hormonal hypersecretion, pituitary hormonal failure, vision loss, headaches and/or bleeding into the tumor (apoplexy).

  • Hormonal hypersecretion: The three most common hormonally active adenomas are Prolactinomas, GH-Secreting Tumors causing Acromegaly, and ACTH-secreting tumors causing Cushing’s Disease. Thyroid stimulating hormone (TSH) tumors are relatively rare.
  • Pituitary failure (Hypopituitarism): This problem typically occurs only in larger tumors (macroadenomas) and results from compression and damage to the normal pituitary gland from the enlarging adenoma. Manifestations may include hypogonadism (sexual dysfunction, loss of libido, and impotence), Hypothyroidism (fatigue, weakness, weight gain, coarse dry hair and dry skin, cold intolerance, depression), Adrenal Insufficiency (fatigue, weakness, loss of appetite, dizziness, nausea and vomiting), growth failure (in children and adolescents), hyperprolactinemia due to "stalk effect" (seen in diseases within or near the pituitary gland and stalk, interfering with the delivery of dopamine, a neuron-transmitter, from the hypothalamus to the prolactin secreting cells of the pituitary gland), which can result in hypogonadism and its associated problems. Rarely posterior pituitary gland damage occurs with diabetes insipidus, which is caused by the inability of the kidneys to conserve water leading to frequent urination and thirst. Learn More.
  • Neurological problems: Larger pituitary macroadenomas often cause loss of visual acuity or peripheral vision (termed bitemporal hemianopsia) from pressure on the optic nerves and optic chiasm which is directly above the pituitary gland. Larger macroadenomas especially those that have hemorrhaged (apoplexy) may also cause double vision.
  • Headache: Patients with macroadenomas often have frontal, forehead and temporal area headaches.
  • Bleeding (pituitary apoplexy): This condition develops over hours to several days from hemorrhage and/or infarction of pituitary adenoma (typically a macroadenoma). Symptoms may include headache, nausea, visual loss, double vision and confusion. Most patients have undiagnosed hormone insufficiency prior to the apoplectic event. Apoplexy is best confirmed by MRI. A head CT will also show areas of bleeding or a mass in the sella in the majority of cases. Other conditions that can mimic pituitary apoplexy are a ruptured aneurysm, meningitis, a stroke, intracerebral hemorrhage and migraine headache. The treatment for most patients with pituitary apoplexy is urgent endonasal transsphenoidal surgery and replacement of the stress hormone cortisol.


Pituitary adenomas are best diagnosed by imaging studies and hormonal testing.

  • Imaging: The imaging study of choice is an MRI of the pituitary gland without and with gadolinium (a contrast agent). A brain MRI or CT scan will also reveal most pituitary macroadenomas but may not reveal smaller microadenomas. In a minority of patients it may be difficult to distinguish an adenoma of the pituitary from other masses which may include Craniopharyngioma, Rathke’s Cleft Cyst, Meningioma, Hypophysitis (pituitary inflammation), Glioma of the suprasellar region, Metastatic Tumor or Chordoma.
  • Hormonal Testing: Evaluation of Pituitary Gland Function either for under-production (hypopituitarism, or pituitary failure) or over-production of hormones should include blood levels of ACTH, cortisol, TSH, free T4 (thyroid function), LH (luteinizing hormone), FSH (follicle-stimulating hormone), estradiol in women, testosterone in men, GH (growth hormone), IGF-1 (insulin-like growth factor, growth hormone's target hormone, also known as somatomedin-C), and prolactin. Given that some tests need to be performed at a certain time of the day, and stimulation tests may be needed to diagnose some endocrine-active tumors (Cushing’s disease or acromegaly), this testing should be overseen by an endocrinologist.
  • Ophthalmological Evaluation: Patients with visual complaints or those whose tumors that contact the optic nerves or optic chiasm should receive a full ophthalmological evaluation. This evaluation should include acuity (vision quality) testing of each eye and formal visual field testing to determine if there is loss of peripheral vision.


  • Endonasal Endoscopic Surgery: The first-line treatment for all pituitary adenomas except prolactinomas (as discussed below), as well as RCCs and many craniopharyngiomas is endonasal transsphenoidal surgery. Because of improved tumor visualization, the endonasal endoscopic approach is rapidly becoming the preferred method for removal of the great majority of pituitary adenomas, RCCs, most craniopharyngiomas and chordomas as well as many midline meningiomas. Surgical success rates are generally quite high (80-90%) with smaller and non-invasive pituitary tumors, and lower with larger and/or invasive tumors (30-70%). Major surgical complications such as vision loss, bleeding, stroke, cerebrospinal fluid leak and meningitis are low when performed by experienced endonasal transsphenoidal neurosurgeons who often work collaboratively with a Head & Neck surgeon. The success rates of surgery are described further in the sections below for specific tumor types.
  • Transcranial surgery: A craniotomy is required in less than 1% of cases for pituitary adenoma.
  • Medical and Radiation therapies: Please see specific tumor types. Acromegaly, Cushing’s Disease, Prolactinoma, Endocrine-Inactive.

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