Magnetic resonance imaging is a special form of imaging the body's internal structures, taken with the person enveloped in a huge and powerful magnet; a picture is built up of any cross-section, or series of cross-sections, through the body, using a technique that detects and pictures structures by their different content of atoms with certain resonances to induced magnetic fields. Particularly useful for investigation of the anatomy of the pituitary gland and hypothalamus when a tumor is suspected. More expensive and less widely available than a CT scan, which gives adequate results in most cases.

A special form of x-ray taken with the person enveloped in the x-ray apparatus, which builds up a particularly good image of any cross-section or series of cross-sections through the body, by a process of computed tomography. Particularly useful for investigation of the anatomy of the pituitary gland and hypothalamus when a tumor is suspected or needs to be excluded. More widely available than an MRI scan, which can give even clearer results.

A tumor, usually benign, of the pituitary gland, usually resulting in amenorrhea and anovulation. Often there is an increase (sometimes substantial) in serum prolactin. If the tumor is itself secreting prolactin it is called a prolactinoma. But other tumors can occur, some of which secrete other pituitary hormones. The tumor grows inside a confined space with walls of bone called the pituitary fossa: if it is still small and confined to the fossa we call the tumor a microadenoma; if it enlarges the fossa or pushes out of it, it is a macroadenoma, and is both more dangerous and capable of producing visual symptoms and headaches. Diagnosed on a CAT scan or a MRI scan. Prolactin-secreting microadenomas can usually be treated just with drugs.