Glucose Tolerance Test to exclude Acromegaly

Availability:
North Devon District Hospital (Mon-Fri)

Target Turnaround Time
5 working days

Clinical Indication
Clinical suspicion of acromegaly or gigantism

Procedure
Prepare a solution of glucose to drink – adults are given a 75g anhydrous solution (1.75g/kg body weight if this is being performed on a child). A pre-prepared solution may be available from pharmacy for this purpose.
The patient should remain at rest throughout the duration of the test.
- Collect a basal sample for growth hormone (gold top) and glucose (grey top)
- Ensure the patient drinks the solution within 5 minutes.
- Take paired samples (1 gold top, 1 grey top) at 30 minutes, 60 minutes, 90 minutes and 120 minutes after the glucose drink has been consumed.
- Send all samples together to the laboratory with one request form for the series. Please indicate the time of sampling on each bottle e.g. 0/30/60/90/120

Clinical Report
Reported as a series of results in conjunction with glucose results. Normal response is to suppress GH production during the test.
Fasting growth hormone may be normal in 8% of acromegalic subjections, but growth hormone does not suppress to undetectable values during the test.

Special Requirements & Notes
The patient is advised to fast for 10-12 hours prior to the test. Small quantities of water are permissible.

Factors affecting result interpretation
This test is contraindicated in patients with diabetes
GH may fail to suppress for a range of reasons. These include: chronic renal failure, liver failure, active hepatitis, anorexia nervosa, malnutrition, hyperthyroidism, diabetes and adolescence.