Hyperglycemia suppresses GH secretion in normal individuals. This principle is used in evaluating individuals with abnormally elevated levels and those who are believed to be hypersecreting GH but who show normal levels on routine serum GH determinations. Administration of a glucose load that produces hyperglycemia should decrease serum GH levels within 1 to 2 hours. In individuals who are hypersecreting GH, a decrease in serum GH will not occur in response to hyperglycemia. Note that the test may require repetition to confirm results.

• Factors that may affect serum GH determinations may also alter results of GH suppression tests.

• Elevated serum GH levels
• Signs of GH hypersecretion with serum GH levels within normal limits
• Confirmation of GH hypersecretion as indicated by decreased response to GH suppression

Nursing Care Before the Procedure

Initial client preparation is the same as that for serum GH determinations.

• The client should be informed that it will be necessary to drink an oral glucose solution and that two blood samples will be obtained.

A venipuncture is performed and a sample collected in a red-topped tube. The sample is handled gently to avoid hemolysis and sent to the laboratory immediately.

The glucose solution (usually 100 g) is administered orally. If the client is unable to drink or retain the glucose solution, the physician is notified. IV glucose may be administered, if necessary, to perform the test.

After 1 to 2 hours, depending on laboratory procedures, a second blood sample is collected in a red-topped tube and sent to the laboratory immediately.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for serum GH determinations.

• Complications and precautions: Monitor for hyperglycemia after ingestion of the glucose solution.