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Non-functioning tumors - Clinical Presentation

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Patients with non functioning pituitary tumors present with symptoms due to the size and location of the tumor, symptoms due to deficiency of pituitary hormones, or a combination of these two effects:

Symptoms due to the size and location of the tumor. Any pituitary tumor (or any other tumor or other disease affecting the pituitary region) can cause headaches. Headaches may vary from mild to severe, and the severity is not always proportional to the size of the tumor. The headaches may be localized behind the eyes, or be more generalized, and can be mistaken for other types of headaches such as tension or migraine headaches. Since these tumors are usually slow growing, and often become quite large before they are discovered, the headaches are often present for many years.

Another common symptom due to the size and location of the tumor is decreased vision. This tends to be a decrease in peripheral vision (termed "temporal visual field defects"), although other types of visual loss may also occur. This is due to the tumor growing upward and pressing on the optic chiasm, a nerve that carries visual information from the eyes to the brain. The decrease in peripheral vision may be quite extensive without the patient realizing it, since people tend to rely on central, rather than peripheral, vision for most daily activities. Other, less common vision problems due to pituitary tumors include double vision when looking up, down, or to the side. This is due to the tumor growing outward to the side and pressing on the nerves that control eye muscle movement.

Symptoms due to loss of normal pituitary hormones. As nonfunctioning pituitary tumors grow, they compress the pituitary gland and interfere with normal pituitary hormone production. This can lead to deficiencies in the hormones that control sexual and reproductive function, the thyroid gland, the adrenal glands, and (rarely) water balance. Deficiencies of these hormones cause specific symptoms that are described in a separate section (see "hypopituitarism").

One pituitary hormone that can be increased, rather than decreased, by nonfunctioning tumors, is prolactin. It is not unusual to see mild to moderate elevations in blood prolactin levels (up to 200 ng/ml) (normal 5-20 ng/ml)in patients with large nonfunctioning pituitary tumors. The source of the prolactin in this case is not the tumor, but normal pituitary tissue that increases its prolactin production when the inhibitory effects of the brain are interrupted by the growing tumor. This can cause confusion among care providers who are not experienced in the evaluation of patients with pituitary tumors. The patient with a large nonfunctioning tumor and a mildly elevated prolactin level can be misdiagnosed as having a prolactin-secreting pituitary tumor. This is an important mistake, because prolactin-secreting tumors are treated with medication, rather than surgery. The medication used for prolactin-secreting tumors will also lower blood prolactin levels in patients with nonfunctioning tumors, but the medication will not treat the tumor itself. In that case, the tumor may continue to grow while the patient and care provider are falsely reassured by the lower prolactin levels in the blood. For this as well as other reasons, it is recommended that patients with large pituitary tumors be evaluated by endocrinologists experienced in pituitary tumors.