Pathophysiology
Clinical meaning
Pituitary adenomas are benign tumors of the anterior pituitary gland that cause disease through hormone hypersecretion, mass effect, or both. Functioning adenomas produce excess hormones: prolactinomas (most common, 40%) cause galactorrhea and amenorrhea; GH-secreting adenomas cause acromegaly (adults) or gigantism (children); ACTH-secreting adenomas cause Cushing disease; and TSH-secreting adenomas cause central hyperthyroidism. Non-functioning adenomas (30%) present with mass effect symptoms: compression of the optic chiasm causes bitemporal hemianopsia (loss of peripheral vision in both eyes), while compression of the normal pituitary causes hypopituitarism. Macroadenomas (โฅ10 mm) are more likely to cause visual field defects and headaches, while microadenomas (<10 mm) typically present with hormonal symptoms alone.