How is an overactive pituitary diagnosed?
Your doctor will ask you about your medical history and any symptoms you are having. He or she may order laboratory tests to measure the levels of hormones in your blood or urine. Various diagnostic tests will be performed depending on the underlying disorder that may be present.
- If a prolactinoma is suspected, tests will be performed to measure prolactin levels in the blood. Hypothyroidism (an underactive thyroid) can also cause elevated prolactin levels, so tests should be done to rule out this possibility.
- In the case of acromegaly, blood levels of growth hormone are usually elevated. GH levels can change over time because the pituitary gland secretes the hormone in spurts. Often an oral glucose tolerance test is performed to diagnose acromegaly. Healthy people experience a drop in blood GH levels after drinking glucose, unlike people with acromegaly.
- In the case of Cushing’s syndrome, tests may be ordered to rule out other causes, such as a tumor on the adrenal gland or the use of glucocorticoid drugs. Other tests include the high-dose dexamethasone suppression test and specialized blood sampling, in which a blood sample is taken from the veins of the sinuses that drain blood from the pituitary gland.
- If laboratory diagnostic tests suggest that a tumor is present, radiologic imaging tests will be performed to determine the size and location of the tumor. Usually magnetic resonance imaging (MRI) is more sensitive in this case than a computerized tomography (CAT) scan. CAT scans may be used with patients who cannot undergo MRI, such as those with pacemakers or other implants.