The OGTT is the primary test used for the diagnosis of GH hypersecretion. After an overnight fast, 75 to 100 g of oral glucose will cause a suppression of serum GH. Blood samples are obtained every 30 minutes for 2 hours. Using an ultrasensitive assay, failure of GH to suppress to below 0.4 ng/mL is diagnostic of acromegaly. However, because many GH assays do not have adequate accuracy to measure low GH levels, a cutoff for nadir GH during OGTT below 1 µg/L is acceptable for excluding the diagnosis

Includes: 3 tests