Pituitary tumors are abnormal growths that develop in the pituitary gland, a small, pea-sized organ located at the base of the brain, behind the nose. This gland plays a central role in the body’s endocrine system, producing hormones that regulate numerous bodily functions, including growth, metabolism, and reproduction. Most pituitary tumors are benign, meaning they are non-cancerous and do not spread to other parts of the body. Understanding how these growths typically behave is important for individuals diagnosed with them, as their growth rate can influence symptoms and management strategies.
Typical Growth Patterns
Most pituitary tumors are slow-growing and are medically referred to as pituitary adenomas. Many individuals can have a pituitary adenoma without experiencing any symptoms, often discovering the tumor incidentally during imaging scans performed for unrelated health concerns. These incidentally found tumors, sometimes called incidentalomas, can remain small and inactive for long periods, potentially never requiring treatment. Their growth typically occurs over years rather than weeks or months, with some studies indicating an average growth rate of approximately 0.33 milliliters per year.
Factors Influencing Growth Rate
The rate at which a pituitary tumor grows can be influenced by several factors. Pituitary tumors are primarily classified as functional (producing excess hormones) or non-functional. Functional tumors can cause symptoms from hormone imbalance even when small. Non-functional tumors cause symptoms by pressing on surrounding structures as they grow.
Tumor size at diagnosis also plays a role; tumors are classified as microadenomas (smaller than 10 millimeters) or macroadenomas (larger than 10 millimeters). Macroadenomas are more likely to cause symptoms due to pressure effects. Different types of functional tumors, such as prolactinomas (producing prolactin), somatotropinomas (producing growth hormone), and corticotropinomas (producing ACTH), can have varying growth tendencies and responses to treatment. Null cell adenomas, which are non-functional, are often the most common type and primarily cause issues through mass effect. Individual patient factors like age or overall health may also contribute to the tumor’s behavior.
Symptoms of Tumor Growth
As a pituitary tumor grows, it can manifest symptoms in two main ways: through pressure on nearby structures or through hormonal imbalances. Growing tumors can exert pressure on surrounding brain tissues, particularly the optic nerves located directly above the pituitary gland. This pressure can lead to vision problems, such as a loss of peripheral vision, blurred vision, or double vision. Headaches are also a common symptom that may arise from the tumor’s increasing size.
If the tumor is functional, its growth and activity can lead to an excess or deficiency of specific hormones, causing a range of symptoms throughout the body. For instance, an overproduction of prolactin can cause irregular menstrual cycles in women or lactation in non-pregnant individuals. Excess growth hormone can lead to enlarged hands, feet, and facial features in adults, a condition called acromegaly. Conversely, a large tumor can also disrupt normal pituitary function, leading to a deficiency in hormone production, which might result in fatigue, unexplained weight changes, or changes in menstrual periods.
Tracking Tumor Growth
Monitoring pituitary tumor growth is a standard practice to assess its behavior and determine the need for intervention. Magnetic Resonance Imaging (MRI) scans are the primary method used to visualize the tumor and track any changes in its size over time. Regular follow-up MRI scans allow healthcare providers to observe the tumor’s growth pattern and its relationship to surrounding structures. For small, asymptomatic tumors, active monitoring with periodic MRI scans is often recommended.
In addition to imaging, blood tests are essential for tracking tumor activity, especially for functional tumors. These tests measure the levels of various hormones produced by the pituitary gland or other glands influenced by it, such as prolactin, growth hormone, cortisol, and thyroid hormones. Changes in hormone levels can signal tumor growth or increased activity, even before significant changes are visible on an MRI. The frequency of these scans and blood tests depends on the tumor type, size, symptoms, and whether treatment has been initiated.