Macroadenomas

Macroadenomas are pituitary adenomas with a greatest diameter of 10 millimeters or more. They are classified as functioning (hormone-secreting) or nonfunctioning, depending on the presence of excess pituitary hormones. Macroadenomas arise from the adenohypophysis and may extend beyond the sella turcica, sometimes compressing surrounding structures such as the optic chiasm, leading to visual disturbances.

Clinical features reflect both mass effect and hormonal activity. Mass effect can cause headaches and visual field defects, most commonly bitemporal hemianopia due to optic chiasm compression. Hypopituitarism may result from loss of normal pituitary tissue. Functioning macroadenomas produce excess hormones, with prolactin-secreting tumors (prolactinomas) being the most common; growth hormone–secreting tumors can cause acromegaly or gigantism; adrenocorticotropic hormone–secreting tumors can cause Cushing’s disease; thyrotropin-secreting tumors are rare. Hyperprolactinemia may also occur due to stalk effect, even when the tumor is not a prolactinoma.

Diagnosis relies on imaging and endocrine testing. Magnetic resonance imaging (MRI) identifies tumor size, extent, and relationship to the optic apparatus. Endocrine evaluation includes measurements of prolactin, IGF-1, cortisol with ACTH, thyroid function, and other pituitary axes, with dynamic testing as needed to determine functionality.

Management typically involves transsphenoidal surgical resection to relieve mass effect and remove tumor. Medical therapy is used for functioning tumors, most notably dopamine agonists (e.g., cabergoline) for prolactinomas, and may be part of treatment for residual or recurrent disease. Radiotherapy or stereotactic radiosurgery can be adjunctive in residual, recurrent, or in patients unsuitable for surgery. Long-term follow-up with MRI and pituitary function tests is recommended to assess response and detect recurrence.