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Acromegaly - Diagnosis

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How is Acromegaly Diagnosed?

With acromegaly, you have higher than normal levels of growth hormone circulating in your blood due to continual overproduction by a tumor. To diagnose the condition, physicians must test your level of growth hormone. There are two ways this is commonly done.

IGF Test
Growth hormone secretion by the pituitary gland into the bloodstream leads to the production and release of insulin-like growth factor-one (IGF-I) from the liver and other tissues. If GH levels are high, IGF-I levels will also be high. Because IGF-I levels are much more stable over the course of a day than GH levels, this is often a more reliable test. The IGF-I test can be done with a single blood draw at any time of day, and need not be a fasting sample. For these reasons, it has become the first test ordered to investigate excessive growth hormone secretion in many cases.

Glucose Tolerance Test
Growth hormone production fluctuates widely throughout the day but is normally suppressed after sugar-containing food or drink is eaten or drunk. For patients with acromegaly, sugar consumption will not reduce the high levels of the hormone, as it does for patients without acromegaly. The glucose tolerance test is very reliable and is usually done in initial investigations for the condition. You will take a sugary drink and the doctor will then take and test blood for sugar and growth hormone at intervals over 2 hours.

Click on the graph to compare non-acromegalic and acromegalic GH levels.

Acromegalic and non-acromegalic GH levels

Pituitary Function
If acromegaly is confirmed from the results of the tests above, the doctor will want to check that the non-tumor part of your pituitary gland is still functioning correctly. To do this he or she tests your blood for other pituitary hormones. If some are low or missing altogether they will be replaced with specific hormones – pills or injections that may need to be taken for the rest of your life.

Scan
Next, the doctor will want to see exactly where and how big the pituitary tumor is. To do this an MRI scan is used. This type of brain scan is not painful. However, it requires the patient to lie in the tunnel-like scanner for about half an hour. A sedative can be provided if you are claustrophobic or anxious about it.