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Pituitary Adenoma

What You Should Know About Pituitary Tumor (Adenoma)

The UCLA Pituitary Tumor Program offers comprehensive management of pituitary adenomas

  • Pituitary adenomas are typically benign, slow-growing tumors that arise from cells in the pituitary gland.
  • The pituitary gland is considered to be the master gland that regulates the body's hormones. 

  Illustration showing the relationship of a pituitary tumor to the optic nerve. The hypothalamus, the part of the brain just above the pituitary gland, regulates pituitary function

General facts about pituitary tumors

  • Pituitary adenomas are relatively common, accounting for approximately 15 percent of primary brain tumors.
  • Most pituitary tumors are benign and are called adenomas.
    • Pituitary adenomas are typically slow growing, but can invade adjacent structures (the cavernous sinus, an area where the carotid arteries run)
    • Pituitary carcinomas, a malignant tumor, are rare.
  • Pituitary adenomas have separate names based on their size
    • A microadenoma are less than 1 cm in diameter
    • A macroadenoma is larger than 1 cm in size

  Midline, side-view MRI images from three different patients with pituitary adenomas. The images on the right side have colorized to better show the tumor in red. The upper pair of images demonstrates how a small microadenoma can be difficult to detect. In this case, the 3-T MRI study performed at UCLA demonstrated this tiny tumor in a Cushing's disease patient that was not seen on MRI scans performed at a different hospital. The middle and lower panels show how larger pituitary adenomas can grow upward toward the brain, and sometimes additionally into the nasal cavity. 

  • Most pituitary adenomas occur spontaneously, meaning they are not inherited.
    • Cases of familial pituitary tumors, or inherited tendencies to develop pituitary adenomas, are rare.
    • Multiple Endocrine Neoplasia type 1 (MEN 1) is a rare condition characterized by simultaneous tumors of the pituitary, pancreas and parathyroid glands. Pituitary adenomas develop in 25 percent of patients with MEN 1.

 

Symptoms Caused by Pituitary Adenomas

Pituitary adenomas are generally thought of as either hormone-producing or hormone-inactive tumors

  1. Hormone-producing pituitary adenomas produce an active hormone in excessive amounts. Patients usually present with symptoms related to the hormonal imbalance
  2. Hormone-inactive (non-functional) pituitary adenomas typically cause problems related to the size of the tumor pushing on surrounding brain structures
    • Large pituitary tumors can compress the normal pituitary gland and cause pituitary failure. This is why is it important to obtain a comprehensive evaluation of pituitary function if a pituitary tumor is diagnosed.
    • Large hormone-producing pituitary tumors can also cause problems related to compression of brain structures.

Hormone-producing pituitary adenomas

The three most common hormone-producing (called endocrine-active) adenomas are:

  • Prolactin-secreting pituitary adenoma (prolactinoma): over-production of prolactin by the pituitary tumor causes loss of menstrual periods and breast milk production in women.
  • Growth hormone-secreting pituitary adenoma: excessive growth hormone (GH) production causes acromegaly in adults or gigantism in children.
  • ACTH-secreting pituitary adenoma: excessive ACTH hormone produced by the pituitary gland causes Cushing's disease.

Other hormone producing pituitary tumors are very rare

  • Thyroid stimulating hormone (TSH) producing pituitary adenomas cause hyperthyroidism

Symptoms related to the mass effect from large pituitary adenomas

  • Visual Loss
    • When large pituitary adenomas ("macroadenomas") grow upward, the tumor can elevate and compress the optic chiasm.
    • A progressive loss of the outer peripheral vision occurs (called a "bitemporal hemianopsia")
    • When severe, a patient can only see what is directly in front of them
    • Other visual problems can include:
      • Loss of visual acuity (blurry vision), especially if the macroadenoma grows forward and compresses an optic nerve.
      • Changes in color perception
  • Pituitary Failure
    • Compression of the normal pituitary gland can lead to various degrees of pituitary failure (hypopituitarism): Symptoms can include:
      • Sexual dysfunction and/or loss of sex drive
      • Inadequate body cortisol levels, causing low blood pressure, fatigue, and inability to handle stressful situations
      • Low thyroid functioning (hypothyroidism)
  • The "Stalk Effect"
    • Compression of the pituitary stalk, the structure that connects the brain to the pituitary gland, can cause a mild elevation in the hormone prolactin. This can cause irregular menstrual periods. It is important to distinguish "stalk effect" from a prolactinoma.
  • Headache
  • Pituitary Apoplexy
    • Pituitary adenomas can suddenly bleed internally, leading to an abrupt increase in size. In other cases, the tumor can outgrow its blood supply, leading to swelling of the dead tissue. These scenarios are termed "pituitary apoplexy." Pituitary apoplexy generally presents with sudden onset headache and visual loss, and is a surgical emergency.

 

Diagnosis

The diagnosis of a pituitary adenoma is made based on a combination of pituitary function testing (blood hormone levels) and pituitary imaging

  • Pituitary Function Testing
    • The diagnosis of a hormone-producing pituitary adenoma may require the assistance of a pituitary endocrinologist
    • The medical diagnosis of Cushing's disease can be very difficult to make and may require highly specialized tests not available in most hospitals.
  • Imaging
    • Adenomas larger than 4 mm can be reliably detected by MRI scans (using a special pituitary protocol)
    • In some cases, a powerful 3-Tesla MRI scanner may detect smaller tumors not visible using lower magnet strength scanners
    • Although larger adenomas can be seen on computed tomography (CT), an MRI scan is preferred.

 

 

 

 

 

 

 

 

 

Treatment

The optimal treatment of a pituitary adenoma depends on multiple factors, including:

  • Hormone production by the tumor (if present)
  • Size of the tumor
  • How invasive the tumor is into surrounding structures
  • The age and health of the patient

Typically, more than one specialist is involved in the management of pituitary adenomas. The UCLA Pituitary Tumor Program has experts in each of the specialties who work closely together to provide patients the most comprehensive, state-of-the-art medical and surgical treatments

 

  

 

Medical Management

  • Hormone-producing pituitary adenomas should be treated in conjunction with an endocrinologist.
    • Prolactinomas often require only medical (nonsurgical) therapy.
    • Medical therapy can play an important role in the management of Cushing's disease and acromegaly.
  • It may be equally important to address pituitary failure (hypopituitarism), especially prior to surgery
    • Inadequate cortisol or thyroid levels can be life-threatening if not recognized prior to surgery
  • UCLA has world-class endocrinologists who are available for consultation

 

Surgical Management

  • The vast majority of pituitary adenomas that require surgery are best removed through the nose. This minimally-invasive technique leaves no facial scar
  • UCLA neurosurgeons are experts in advanced endoscopic techniques, that are generally more effective in removing all the tumor while at the same time minimizing complications, hospitalization time, and discomfort. Our surgeons also have extensive experience with traditional techniques using the operating microscope
  
Radiation therapy
  • Stereotactic radiotherapy is a technique in which a high dose of radiation can be delivered to the tumor target. Remarkably, the surrounding brain structures receive only a fraction of the radiation dose and are typically unharmed (with the exception of the normal pituitary gland).
  • UCLA uses the advanced Novalis TX Shaped Beam radiation delivery system, which allows treatment of irregularly shaped tumors that are close to critical brain structures.
  • One of the main drawbacks of radiation treatment is that it leads to delayed pituitary failure. This typically occurs several years after treatment, necessitating complete hormone replacement.
  • Radiation therapy is typically reserved for pituitary tumors that cannot be cured surgically and are not controlled with medical drug therapy
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