When acromegaly is suspected, securing biochemical evidence is imperative. Diagnostic tools used to determine a diagnosis include the following:1
- Blood test to measure serum insulin-like growth factor-1 (IGF-1) — Acromegaly in the absence of elevated IGF-1 levels is rare, which is why according to the American Association of Clinical Endocrinologists (AACE) Acromegaly Guidelines, this test is ideal for diagnosis. It's also considered useful for measuring IGF-1 levels following treatment, such as surgery.2
- Oral glucose tolerance test (OGTT) –– For almost 40 years the measurement of growth hormone (GH) during an oral glucose test has been standard. Following ingestion of a glucose drink, GH levels in normal patients should fall below 1 ng/mL. In patients with acromegaly, oral glucose does not suppress GH.2
- Random GH testing –– While GH levels are usually elevated in the presence of acromegaly, serum concentrations can fluctuate, so a 24-hour sample is necessary to make this test useful.2
- Imaging –– Following a diagnosis of acromegaly by measuring GH or IGF-I levels, a magnetic resonance imaging (MRI) scan of the pituitary may be used to locate and detect the size of the tumor causing GH overproduction. If a patient cannot have an MRI, computerized tomography (CT) scans can be used as well, though an MRI is considered a more sensitive technique.1
References:
1.
National Institute of Diabetes and Digestive and Kidney Diseases. Acromegaly. Available at: www.endocrine.niddk.nih.gov/pubs/acro/Acromegaly.pdf - 06-10-2008. Accessed June 11, 2009.
2.
American Association of Clinical Endocrinologists Medical guidelines for clinical practice for the diagnosis and treatment of acromegaly. Endocrine Practice. 2004;10:213-225.
