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Arginine (Growth-Hormone-Stimulation Test)
Arginine (Growth-Hormone-Stimulation Test)
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Arginine (Growth-Hormone-Stimulation Test)
Category: Hormones.
Subcategory: Pituitary hormones.
Material studied: Blood.
Estimated cost of test: $52.00.
Patient time for test: 5-10 minutes.
Reliability of test results: Good.
Available as home self-test? No.
Note: Test measures changes in growth hormone after endocrine system is stimulated by arginine. Test is used commonly to study children with retarded growth.
BEFORE THE TEST
Purpose of test:
Confirms growth-hormone deficiency in children and infants.
Helps confirm diagnosis of pituitary tumors*.
Where is test performed?
Commercial laboratory, hospital, doctor's office.
Who performs test?
Lab technician, nurse, doctor.
Risks and precautions:
If tourniquet is applied on the arm too long (over 1 minute), it may cause an inaccurate test result. Request another sample to be collected to ensure accuracy.
Patient preparation:
Activity--Limit physical activity for 10 to 12 hours before the test. You will be asked to lie down and relax for 90 minutes before the test.
Diet--Don't eat any food or drink any liquid for at least 12 hours before the test.
Medicines--Inform the person performing the test if you have recently taken any medications listed under Taking these drugs may affect test results. You may be asked not to take this medication before the test.
Disrobing--None required. Roll up sleeve only.
THE TEST
Sensory factors:
Touching--You will feel mild discomfort when the needle is inserted into the vein or when the lancet pricks a finger, heel or ear lobe.
Seeing--You will see the technician, nurse or doctor, the basket or tray to hold the equipment, the needles, syringes, collecting tubes and bandages.
Feeling--Some degree of apprehension or fear is normal and should be expected. Discomfort disappears when the test is finished.
Other senses (taste, smell, hearing)--Not affected.
Equipment used:
Needles, syringes and heparinized* collecting tubes. Sterile, disposable equipment prevents contamination or spread of infection. There is no risk of becoming infected with the hepatitis virus, AIDS virus or any other infecting germ.
In-dwelling venous catheter.
Arginine for injection.
Description of test:
Technician, doctor or nurse applies a tourniquet or blood-pressure cuff to the upper arm if blood is collected from a vein.
Skin over the vein to be stuck is cleaned with alcohol or other antiseptic on a piece of cotton.
When blood is drawn from a vein, the operator feels the vein to be used then punctures both the skin and vein in one quick stroke. The needle used is a sterile, disposable needle attached to a sterile, disposable syringe.
Operator withdraws the needle and transfers sample from the collecting syringe into sterile tubes (identified with your name) before sending samples to the laboratory for analysis. Tubes are treated with an anti-coagulant chemical to prevent clotting.
Operator collects a baseline blood sample.
An intravenous catheter is inserted to avoid repeated venepunctures.
Arginine is started intravenously in a different vein and continues for 30 minutes.
After 30 minutes, solution is discontinued.
Operator collects three additional blood samples at 30-minute intervals from the in-dwelling catheter.
AFTER THE TEST
Immediate post-test care:
Apply pressure to the puncture site with cotton provided by the laboratory.
If a vein has been punctured, raise your entire arm over your head while applying pressure.
Some discoloration, soreness or swelling may develop at the venepuncture site. This responds well to moist, warm compresses applied every 2 to 4 hours.
Activity after test:
Resume taking any medications that were withheld before the test.
Return to pretest activities right away.
Use warm compresses if blood collects under the puncture site or if the area becomes tender, red or painful.
Time before test results available: 2 days.
TEST RESULTS
Test values:
Test results are determined by ion- exchange chromatography*.
Normal values:
Men--Over 10ng/ml.
Women--Over 15ng/ml.
Children--Over 48ng/ml.
Increase may appear in first sample drawn 30 minutes after arginine infusion is discontinued or in samples drawn at 60 and 90 minutes.
What ABNORMAL may indicate:
In children, pituitary dwarfism*.
In adults, decreased pituitary functions, sometimes caused by tumors*.
What HIGH or INCREASED may indicate:
No growth-hormone deficiency.
Taking these drugs may affect test results:
Amphetamines.
Beta-blockers.
Calcium gluconate.
Estrogens.
Glucocorticoids.
Methamphetamines.
Pituitary-based drugs.
Progestogen.
Spironolactone.
Steroids.
Other factors that may affect test results:
Ethanol.
Failure to follow diet restrictions, medication restrictions and limitations of physical activity
*See Glossary.
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From Complete Guide to Medical Tests by H. Winter Griffith, M.D. Copyright by Fisher Books. Electronic rights by Medical Data Exchange.
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