The pituitary is a small, pea-sized gland that hangs from the hypothalamus, a structure at the base of the brain, by a thread-like stalk that contains both blood vessels and nerves. It controls a system of hormones in the body that regulate growth, metabolism, the stress response, and functions of the sex organs via the thyroid gland, adrenal gland, ovaries, and testes.
A pituitary tumor is an abnormal growth of cells within the pituitary gland. Most pituitary tumors are benign, which means they are non-cancerous, grow slowly and do not spread to other parts of the body. However, these cells can make the pituitary gland produce too many hormones, which can cause problems in the body. Tumors that make hormones are called functioning tumors, and they can cause a wide array of symptoms depending upon the hormone effected. Tumors that don’t make hormones are called non-functioning tumors.
As tumors enlarge, normal pituitary function is destroyed. This produces various hormonal deficiencies, since the pituitary controls the action of other endocrine glands. Pressure on near-by structures produce headaches, vision problems, nausea, and vomiting. The optic nerves are directly above the pituitary gland and upward growth of pituitary tumors frequently causes progressive visual loss. This visual loss typically begins from each side of the field of vision leading to tunnel vision.
Pituitary tumors often go undiagnosed because their symptoms resemble those of many other common diseases.
Gamma Knife radiosurgery is usually prescribed for a patient left with a small amount of residual tumor following surgical removal. This is particularly important for the patient who has persistent excessive hormone production. Gamma Knife radiosurgery may also be used to treat a small residual non-functioning tumor, particularly if it has recurred. Gamma Knife is usually considered as “adjunctive therapy” – given after surgical removal of as much tumor as possible. The size of the residual tumor is the limiting factor in selecting a patient for this treatment – the tumor cannot be too close to the optic chiasm (eye nerves) because of the risk of damage to vision. A recent MRI study must be reviewed before deciding if the patient is a candidate for Gamma Knife.
Gamma Knife radiosurgery is suitable for the treatment of pituitary adenomas (a benign tumor of glandular origin). Further, treatment given in a single session is more convenient for the patient and is cost effective.