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Several tests are useful in diagnosing and monitoring acromegaly. The most important are laboratory tests that measure the levels of growth hormone (GH) in the blood. Because these levels vary naturally depending on factors (age, the time of day, and when you last ate) there are 2 main approaches to measuring your GH.
- Random GH testing: To compensate for the variation in levels, your doctor may average the values from a series of "random" blood tests.
- Oral glucose tolerance test (OGTT): Alternatively, a way to get an accurate reading in a single measurement is to take the blood sample after you do an overnight fast, followed by an early morning drink of concentrated glucose solution.
Additionally, insulin-like growth factor-1 (IGF-1) levels can be measured, as acromegaly in the absence of elevated IGF-1 levels is rare. These levels vary by age and gender and need to be adjusted accordingly. The test for IGF-1 levels is a blood test.
- Blood test for IGF-1 levels: Because IGF-1 is released more evenly than GH, and these levels remain higher longer, IGF-1 levels can be taken at any time, with a blood test.
- After an OGTT, GH levels should be
- Without an OGTT, an average level of <2.5 ng/mL from multiple random samples is considered normal.
Levels of GH and IGF-1 are often measured in ng/mL, which stands for nanograms per milliliter. The reference numbers can be slightly different depending on the assays used for testing and on the laboratory your health care professional uses. Please talk to your health care professional about your test results and what they mean for you.
Tests for Acromegaly Diagnosis
After acromegaly has been diagnosed, other tests, such as head scans with magnetic resonance imaging (MRI) or computed tomography (CT), are designed to look for a pituitary growth or tumor, the most likely source of the excessive GH secretion. Normally, these tests are performed on an outpatient basis inside a hospital or clinic and involve no special preparation on your part. Head scans are a way to provide your health care provider with "photographs" of the inside of your head.
Additional Tests for Acromegaly Diagnosis
Still other tests, such as an electrocardiogram (ECG), chest X-ray, eye and visual field examination will help your doctor check your overall health. These tests also usually do not require hospitalization and are performed by health care specialists in different fields. These specialists and/or technicians will send all test results directly to your health care provider. Your health care professional will then provide you with your test results, as well as specific information regarding your current levels of GH and IGF-1. It's important to understand the results of all of your tests and learn your GH and IGF-1 levels so that you can become a more knowledgeable patient.