text: Adenomas exceeding  in size are defined as macroadenomas, with those smaller than  referred to as microadenomas. Most pituitary adenomas are microadenomas and have an estimated prevalence of 16.7% (14.4% in autopsy studies and 22.5% in radiologic studies). A majority of pituitary microadenomas often remain undiagnosed, and those that are diagnosed are often found as an incidental finding and are referred to as incidentalomas.
  Pituitary macroadenomas are the most common cause of hypopituitarism.
  While pituitary adenomas are common, affecting approximately one in 6 of the general population, clinically active pituitary adenomas that require surgical treatment are more rare, affecting approximately one in 1,000 of the general population.
  Signs and symptoms
  Physical
  Hormone secreting pituitary adenomas cause one of several forms of hyperpituitarism. The specifics depend on the type of hormone. Some tumors secrete more than one hormone, the most common combination being GH and prolactin, which present as unexpected bone growth and unexpected lactation (in both men and women).
  A patient with pituitary adenoma may present with visual field defects, classically bitemporal hemianopsia. It arises from the compression of the optic nerve by the tumor. The specific area of the visual pathway at which compression by these tumours occurs is at the optic chiasma.