Growth Hormone Testing Care

To prepare for the procedure, most patients will need to:

• Fast for 10-12 hours before the test.
• Reduce physical activity for 10-12 hours before the test.
• If instructed by your doctor, stop taking regularly prescribed medicine before the test.
• Ninety minutes before the test, rest and relax. Avoid physical activity.

The injection site will be cleaned. An elastic tie will be placed around the upper arm. A needle will be inserted into the vein. The blood will be collected in a vial. Once the vials are full, the needle will be removed from the skin. Pressure will be put on the puncture site.

A blood sample will be taken between 6 am and 8 am. You will be asked to drink a water and glucose (sugar) solution. The glucose should make the GH level in the blood lower. Two more blood samples are taken within one to two hours after you have consumed the solution. In each blood sample, the GH level will be measured. IGF-1 levels may also be measured since they do not vary so much.

Blood samples will be drawn five times at different intervals. A first sample for blood glucose, cortisol, and growth hormone will be taken between 6 am and 8 am. Then, insulin will be given through the IV. The insulin should make the blood glucose level go down, which should make the GH level go up. Blood samples will be collected at 30, 60, 90, and 120 minutes for glucose, cortisol, and growth hormone.

If the blood sugar has not dropped to a certain level after 45 minutes, a repeat dose of insulin will be given. The blood sample will be collected 75 minutes and 150 minutes later. If the blood sugar levels fall too low, a high dose of sugar will be given by IV, followed by a sugar infusion.

The blood sample will be drawn five times at different intervals. The first sample will be taken between 6 am and 8 am. Arginine or GH-releasing peptide will be given through the IV for 30 minutes. Once the arginine or GH-releasing peptide has been administered, GH-releasing hormone will be given by IV. This should stimulate the pituitary to release GH. The last four blood samples will be drawn every 30 minutes following both infusions.

You will be able to leave after the test is done.

The procedure often takes at least three hours.

There may be some minor discomfort when the needle is inserted in the skin and during the infusions. A doctor will supervise the insulin tolerance, as insulin can cause a very low blood sugar level in the blood.