Adenomas are classified radiographically by size. Microadenomas are considered to be less than lcm, and macroadenomas, greater than lcm.
Microadenomas are often functional and come to clinical attention due to signs and symptoms of excess hormone secretion (i.e. prolactin, ACTH, or growth hormone).
Adenomas in some patients may undergo haemorrhagic infarction. The enlarged haemorrhagic gland may be dysfunctional and compress adjacent structures, producing pituitary apoplexy.
