Pituitary adenomas are common benign tumors of the pituitary gland. It is said that up to 10% of people will have a pituitary adenoma by the time of their death. Some tumors secrete one or more hormones in excess. Non-invasive and non-secreting pituitary adenomas are considered to be benign. Adenomas which exceed 10 millimetres in size are defined as macroadenomas, with those smaller than 10 mm referred to as microadenomas.