GROWTH HORMONE SUPPRESSION TEST
INTRODUCTION
This test is useful in confirming the presence of active acromegaly or gigantism, particularly in the early stages. In these conditions the normal suppression of growth hormone (GH) by food or glucose does not occur. Although the test appears similar to a full Glucose Tolerance Test the timing of samples are different and additional samples are collected for GH analysis. Urine samples are not required.
PRECAUTIONS
Please refer to the Trust’s phlebotomy procedure for sample collection precautions.
The patient should not be receiving GH stimulating drugs. The test should not be performed on seriously ill patients and those showing metabolic response to trauma and surgery.
PATIENT PREPARATIONS
The patient should fast overnight and during the test. Water is allowed. The patient should be at rest during the test and smoking is not permitted.
Glucose load: |
75g of glucose – available from Pharmacy, dissolved in 300ml of water. |
Children: 1.75g of glucose per kg body weight up to a maximum of 75g. |
PROTOCOL
After OVERNIGHT FAST
1. |
Insert indwelling intravenous cannula and wait at least 30 minutes |
|
2. |
Take basal blood sample for - |
glucose
(minimum 1ml in fluoride tube – grey top) |
3. |
Give the appropriate glucose load (see previous page) orally over a period of 5 minutes. Care should be taken to avoid vomiting. Timing of the test is from the beginning of the drink. |
|
4. |
Take further blood samples for - |
glucose
(minimum 1ml in fluoride tube – grey top) |
| N.B. AT THE END OF THE TEST THERE SHOULD BE 6 GREY TOP AND 6 YELLOW TOP TUBES | ||
INTERPRETATION
Normal Response: serum GH should suppress to <1.25 ug/L at some point during the test.
In patients with active disease, there is a failure of a high basal serum GH to suppress and there may be a paradoxical rise. Often there is evidence of decreased glucose tolerance. A paradoxical rise in GH may also occur in renal failure and diabetes mellitus. Failure of suppression is sometimes seen in advanced liver disease, heroin addiction and anorexia nervosa.
Reviewed by: Tony
Everitt, Consultant Biochemist
Last edited 07/08/08