IGF-1 Levels and Diagnosing Acromegaly

Physicians can also measure IGF-1 levels in patients with suspected acromegaly. Elevated GH levels increase IGF-1 blood levels. Because IGF-1 levels are much more stable over the course of the day, they are often a more practical and reliable measure than GH levels. Elevated IGF-1 levels almost always indicate acromegaly. However, a pregnant woman's IGF-1 levels are two to three times higher than normal. In addition, physicians must be aware that IGF-1 levels decline in aging people and may be abnormally low in patients with poorly controlled diabetes mellitus.

 

Imaging Tests Used in Diagnosing Acromegaly

After acromegaly has been diagnosed by measuring GH or IGF-1 levels, imaging techniques, such as computed tomography (CT) scans or magnetic resonance imaging (MRI) scans of the pituitary, are used to locate the tumor that is causing GH overproduction. Both techniques are excellent tools to visualize a tumor without surgery. If scans fail to detect a pituitary tumor, the physician should look for non-pituitary tumors in the chest, abdomen, or pelvis as the cause for excess GH. The presence of such tumors usually can be diagnosed by measuring growth hormone-releasing hormone (GHRH) in the blood and by a CT scan of possible tumor sites.