A macroadenoma is a growth that develops in the pituitary gland, a small, pea-sized organ located at the base of the brain, behind the nose. These growths are noncancerous and do not spread to other parts of the body. While slow-growing, their presence can lead to various health issues depending on their size and whether they produce hormones. This article covers their nature, symptoms, diagnosis, and management strategies.
What is a Macroadenoma?
A macroadenoma is defined by its size, measuring greater than 10 millimeters (1 centimeter) in diameter. This differentiates it from a microadenoma, which is smaller than 10 millimeters. These growths originate from the glandular tissue of the pituitary gland itself. The pituitary gland, often called the “master gland,” produces and releases hormones that regulate many bodily functions, including growth, metabolism, blood pressure, and reproduction. While macroadenomas are tumors, they are almost always noncancerous and do not spread. They can, however, still cause health problems by pressing on surrounding structures in the brain or by secreting an excess of hormones.
Recognizing the Signs
The symptoms of a macroadenoma can vary widely depending on its size and whether it produces hormones. One category of symptoms arises from the tumor’s physical presence, known as a “mass effect.” As a macroadenoma grows, it can press on nearby brain structures, leading to headaches, dizziness, nausea, or even seizures. Compression of the optic chiasm, where optic nerves cross, can cause vision problems, including loss of side (peripheral) vision or double vision.
Another set of symptoms results from hormonal imbalances if the macroadenoma is “functioning,” meaning it secretes excess hormones. For instance, a tumor producing too much prolactin (a prolactinoma) can lead to irregular menstrual periods or milk production in women and erectile dysfunction in men. Excess growth hormone can cause acromegaly in adults, characterized by enlarged hands, feet, and facial features, along with joint pain and increased sweating. If the tumor produces too much adrenocorticotropic hormone (ACTH), it can lead to Cushing’s disease, presenting with weight gain, a rounded face, thin skin, and muscle weakness. Conversely, a large macroadenoma can also disrupt normal pituitary gland function, leading to a deficiency in one or more hormones, resulting in symptoms like fatigue, weight changes, or sensitivity to cold.
Confirming a Diagnosis
Identifying a macroadenoma involves a combination of medical evaluations. A healthcare provider will begin by discussing a person’s symptoms and conducting a physical examination. Imaging techniques are important for visualizing the tumor.
Magnetic Resonance Imaging (MRI) of the brain is the preferred imaging method to detect a pituitary tumor, providing detailed images of its location and size. Blood tests are also an important part of the diagnostic process, as they can reveal abnormal levels of various hormones, such as prolactin, growth hormone, cortisol, and thyroid hormones. These hormone levels help determine if the tumor is functioning and which specific hormone it might be overproducing. In some cases, a 24-hour urine test may be used to measure cortisol levels, particularly if Cushing’s disease is suspected. Specialists like endocrinologists, who focus on hormone disorders, and neuro-ophthalmologists, who specialize in vision problems related to the nervous system, often collaborate in the diagnostic process.
Managing the Condition
Management of a macroadenoma depends on several factors, including the tumor’s size, the type of hormones it produces (if any), the symptoms it causes, and the patient’s overall health. Surgical removal is a common approach, particularly for larger tumors or those causing mass effect symptoms like vision problems. Transsphenoidal surgery, a minimally invasive procedure performed through the nasal cavity, is frequently used to remove the tumor, aiming to relieve symptoms and restore hormone function.
Medical management is often the primary treatment for certain types of macroadenomas, especially prolactinomas. Dopamine agonists like cabergoline or bromocriptine are effective in reducing prolactin levels and shrinking these tumors, often making surgery unnecessary. Cabergoline is preferred due to its more effective and fewer side effects compared to bromocriptine. For other functioning tumors, such as those producing growth hormone or ACTH, medications may be used to control hormone levels, sometimes in conjunction with surgery.
Radiation therapy, including stereotactic radiosurgery, may be considered as a supplementary treatment after surgery or if surgery is not an option. This therapy uses focused radiation beams to target the tumor and control its growth.