Pituitary Macroadenoma

A pituitary macroadenoma is a noncancerous (benign) tumor that develops from hormone-producing cells in the anterior (front) portion of the pituitary, a pea-sized endocrine gland located at the base of the brain. Pituitary adenomas measuring 1 centimeter (10 mm) or larger are classified as macroadenomas, while smaller adenomas are classified as microadenomas.

Although pituitary macroadenoma does not spread (metastasize) to distant parts of the body, it can significantly affect health. As the tumor enlarges, it may compress nearby structures, particularly the optic chiasm where the optic nerves partially cross. The pressure may cause vision problems, headaches and other neurological symptoms. Some macroadenomas also produce excess hormones, which can disrupt normal endocrine function and contribute to conditions such as acromegaly, Cushing disease or hyperprolactinemia. Even a nonfunctioning macroadenoma, which does not produce excess hormones, can interfere with the pituitary’s ability to regulate essential hormones throughout the body.

Pituitary adenomas account for approximately 10% to 15% of all tumors that develop within the skull (intracranial tumors). Because these tumors often grow slowly, some remain undetected until they become large enough to cause symptoms or are discovered during imaging performed for an unrelated reason.

Causes and risk factors for pituitary macroadenoma

The exact cause of pituitary macroadenoma is unknown. Researchers believe that most tumors of this type develop after genetic changes occur within individual pituitary cells during a person’s lifetime rather than being inherited. These changes can disrupt normal cell growth, allowing pituitary cells to multiply and form a tumor.

There are no established modifiable risk factors for pituitary macroadenoma. No lifestyle habits or environmental exposures have been proven to increase the risk, and there are currently no known strategies for preventing these tumors.

Known or suspected nonmodifiable risk factors include:

• Inherited genetic factors – Rare hereditary conditions, including multiple endocrine neoplasia type 1 (MEN1), familial isolated pituitary adenoma (FIPA) and Carney complex, are associated with genetic alterations that can increase the likelihood of developing pituitary adenomas.
• Family history – Having one or more close relatives with pituitary adenomas or certain hereditary endocrine tumor syndromes may indicate an increased predisposition.

Signs and symptoms of pituitary macroadenoma

Pituitary macroadenoma symptoms can vary depending on the tumor’s size, growth rate, location and whether it produces excess hormones. Some tumors cause few or no symptoms until they become large enough to affect normal pituitary function or compress nearby structures.

Early signs of a pituitary macroadenoma

Early symptoms may be subtle and develop gradually, particularly when a macroadenoma grows slowly. These may include:

• Mild or intermittent headaches
• Fatigue or low energy
• Menstrual irregularities or infertility
• Decreased libido
• Erectile dysfunction
• Breast milk production unrelated to pregnancy or breastfeeding (galactorrhea)
• Enlargement of the hands or feet, facial changes and other symptoms associated with excess growth hormone
• Unexplained weight gain and other symptoms associated with excess cortisol
• Cold intolerance and other symptoms associated with reduced pituitary hormone production

Signs of a large or growing pituitary macroadenoma

As a macroadenoma enlarges, it may compress normal pituitary tissue, the optic chiasm and other nearby structures, potentially leading to:

• Progressive loss of side (peripheral) vision
• Blurred or double vision
• Persistent or worsening headaches
• Nausea or vomiting
• Symptoms associated with deficiencies of one or more pituitary hormones
• Facial numbness or weakness if certain nearby nerves are affected
• Sudden severe headache, vision loss or changes in consciousness due to pituitary apoplexy, a medical emergency that can occur when a pituitary tumor suddenly bleeds or loses its blood supply

How pituitary macroadenoma is diagnosed

Diagnosis of a pituitary macroadenoma often begins when symptoms such as headaches, vision changes or signs of a hormone imbalance prompt medical evaluation. Some tumors are discovered incidentally during brain imaging performed for another reason. If a pituitary tumor is suspected, the diagnostic process may include:

• Medical history and physical examination – The physician will evaluate symptoms and neurological function and check for signs of hormone excess or deficiency that may indicate a pituitary tumor.
• Blood testing – Blood tests can measure pituitary hormones and hormones regulated by the pituitary. The results can help determine whether the tumor is producing excess hormones or interfering with normal pituitary function.
• Urine testing – A 24-hour urine collection or other specialized testing may be used to measure cortisol levels if Cushing disease is suspected.
• Magnetic resonance imaging – MRI with contrast is the preferred imaging study for evaluating a suspected pituitary macroadenoma. It can show the tumor’s size and location and whether it is affecting nearby structures, such as the optic chiasm or cavernous sinuses.
• Computed tomography (CT) scan – A CT scan may be used if MRI is not feasible or additional evaluation of surrounding bone structures is needed.
• Visual field testing – Formal visual field testing can detect peripheral vision loss that may occur when a macroadenoma presses on the optic chiasm.
• Pathology evaluation – If surgery is performed, a pathologist will examine the removed tumor tissue and may perform additional testing to classify the adenoma based on its pituitary cell lineage and hormone expression. These findings can help guide follow-up care.

How pituitary macroadenoma is treated

Treatment for pituitary macroadenoma is individualized based on the tumor’s size, location, hormone-producing activity, growth pattern and impact on surrounding structures, as well as the patient’s symptoms and overall health. In many cases, specialists in endocrinology, neurosurgery, radiation oncology, neuroradiology, neuropathology and ophthalmology work together to develop a tailored treatment plan. Options may include:

• Active surveillance – A slow-growing macroadenoma that is not causing significant symptoms, hormone abnormalities or pressure on nearby structures may be monitored with periodic MRI scans, hormone testing and clinical follow-up.
• Surgery – Surgery is often the primary treatment for symptomatic macroadenomas, particularly those compressing the optic chiasm or other nearby structures or causing certain hormone abnormalities. Most pituitary adenoma surgeries can be performed through the nasal passages using a minimally invasive endoscopic transsphenoidal approach, although a different surgical approach may be necessary for a large or complex tumor.
• Medication – Medication may be the primary treatment for certain functioning macroadenomas or may be used when surgery does not fully control hormone production. Dopamine agonists are typically the first-line treatment for prolactin-producing macroadenomas because these drugs can lower prolactin levels and shrink the tumor. Other medications can help control excess growth hormone or cortisol associated with certain functioning tumors. Traditional chemotherapy and immunotherapy are not standard treatments for pituitary macroadenoma.
• Radiation therapy – Radiation therapy may be recommended for residual tumor that cannot be safely removed or for a tumor that continues to grow or recurs after surgery. Techniques such as stereotactic radiosurgery, fractionated stereotactic radiation therapy (FSRT) and intensity-modulated radiation therapy (IMRT) can precisely target the tumor while limiting radiation exposure to nearby healthy tissues.
• Clinical trials – Eligible patients may have access to clinical trials evaluating new medications, radiation delivery techniques and other innovative treatment strategies for complex or recurrent pituitary tumors.

The Moffitt Cancer Center difference for pituitary macroadenoma

Pituitary macroadenoma is a complex condition that can affect both neurological function and the body’s complex hormone system. At Moffitt, the specialists in our Endocrine Program collaborate to provide comprehensive evaluations, advanced imaging, individualized treatment planning and long-term follow-up care tailored to each patient’s needs.

To learn more about pituitary macroadenoma, you can request an appointment with a specialist in Moffitt’s Endocrine Program by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.