The pituitary gland is a small, pea-sized structure located at the base of the brain, often called the “master gland” because it produces hormones regulating bodily functions like growth, metabolism, and reproduction. A pituitary tumor is an abnormal growth of cells within this gland that can disrupt the endocrine system. The vast majority of these growths are benign, meaning they are non-cancerous and do not spread. With modern medical management, most people diagnosed with a pituitary tumor can expect to live a full, normal lifespan.
Understanding the Nature of Pituitary Tumors
Pituitary tumors are overwhelmingly classified as pituitary adenomas, which are benign. Malignant pituitary carcinomas are exceedingly rare, accounting for less than 0.2 percent of all pituitary masses. Adenomas are categorized by size: microadenomas are smaller than 10 millimeters, while macroadenomas exceed this measurement.
The significance of a tumor depends on whether it is functional or non-functional. Functional tumors secrete an excess of pituitary hormones, leading to specific hormonal syndromes. Non-functional tumors do not secrete hormones; they cause symptoms primarily through their physical presence as they grow.
Pituitary adenomas are common, estimated to affect up to 17 percent of the general population. Most are small, non-secreting growths discovered accidentally during imaging for unrelated conditions, termed incidentalomas. These often remain asymptomatic and typically require observation rather than active intervention.
Impact on Body Systems and Daily Function
The effects of a pituitary tumor fall into two categories: hormonal imbalance and physical pressure on surrounding structures. Functional tumors cause hormone excess. For example, prolactinomas cause overproduction of prolactin, leading to infertility, irregular menstrual cycles, or unexpected milk discharge. Tumors secreting excess adrenocorticotropic hormone (ACTH) cause Cushing’s disease, characterized by weight gain, easy bruising, and thin skin.
Excessive growth hormone (GH) secretion causes acromegaly in adults, resulting in the enlargement of hands, feet, and facial features. If a tumor grows large, it can destroy normal pituitary tissue, leading to hormone deficiencies known as hypopituitarism. This condition requires lifelong hormone replacement to supplement low levels of cortisol, thyroid hormone, or sex hormones.
The physical size, or mass effect, of larger tumors (macroadenomas) is the other primary concern. Since the pituitary gland sits beneath the optic chiasm, tumor growth can compress the optic nerves. This compression often causes a progressive loss of peripheral vision, known as bitemporal hemianopsia. The physical bulk of a macroadenoma can also cause persistent headaches due to increased pressure.
Treatment Approaches for Management
Management is customized based on the tumor’s type, size, and whether it causes hormone excess or mass effect. For many functional tumors, especially prolactinomas, medication is the preferred first-line therapy. Dopamine agonists, such as cabergoline or bromocriptine, mimic dopamine to inhibit prolactin release.
These medications suppress prolactin synthesis and secretion, often causing significant tumor shrinkage and sometimes eliminating the need for surgery. Surgery is usually the primary intervention for other functional tumors or for non-functional tumors causing significant mass effect.
The most common surgical technique is transsphenoidal surgery, a minimally invasive procedure. Surgeons access the pituitary gland through the nasal cavity and the sphenoid sinus, a hollow space behind the nose. Using specialized tools, the surgeon removes the tumor without requiring an open craniotomy, thus avoiding contact with the brain.
Radiation therapy is reserved for tumors that cannot be completely removed, recur after treatment, or do not respond to medication. Techniques like stereotactic radiosurgery deliver a highly focused dose of radiation directly to the residual tumor. This focused approach provides excellent long-term tumor control, often exceeding 90 percent for hormone-secreting tumors, while minimizing damage to healthy brain tissue.
Outlook and Ongoing Care
The prognosis for individuals with a pituitary tumor is highly favorable, with a five-year survival rate exceeding 97 percent for most adenomas. Living a near-normal life hinges on consistent, long-term management. Lifelong monitoring is necessary after initial treatment to ensure the tumor does not recur or progress.
Ongoing care involves regular blood tests to check hormone levels and periodic MRI scans to monitor the tumor bed size. If treatment caused hypopituitarism, lifelong hormone replacement therapy for deficient hormones, such as cortisol or thyroxine, is instituted. Replacing these hormones restores normal function and prevents serious complications. Successful management requires establishing a stable, chronic plan with an endocrinologist and neurosurgical team.