Oral Glucose Suppression Test for Growth Hormone Secretory Dynamics

Indication: The oral glucose tolerance test is used for the diagnosis of Acromegaly and to determine remission after surgery. In normal individuals, hyperglycemia suppresses growth hormone secretion.

Procedure:

1. Patient NPO after midnight if possible
2. Insert saline lock into peripheral vein
3. Obtain baseline serum levels for growth hormone, glucose and somatomedin-c using red top tubes
4. Inject 3cc 0.9 NaCL to prevent blood from clotting
5. Administer glucose (100g) orally as glucola over 5 minutes
6. Waste 5cc of blood prior to each blood draw and administer 3cc 0.9 NaCL after obtaining samples
7. Obtain serum blood levels for growth hormone and glucose at 30, 60, 90 and 120 minutes using red top tubes
8. Discontinue saline lock

Interpretation: in normal individuals, glucose suppresses below 2 ng/ml after ingesting 100g of glucola. More sensitive assays require a growth hormone level below 1 ng/ml to rule out acromegaly.

* False positive results can occur in patients with diabetes mellitus, anorexia, liver failure, tall adolescents and individuals with growth hormone resistance disorders.