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Arginine Stimulation GH Response

HGH Response, Growth Hormone Response, Arginine Stimulation

Test Codes

EPIC: LAB1231286, SOFT: ASGHR

Department

Immunology

Instructions

• Stimulation Tests are performed by the Medical Short Stay unit. Contact 248-551-5490, option 2, to schedule an appointment.
• Patient must be fasting and at complete rest for 30 minutes before blood collection.

Specimen Collection Criteria

Collect: One Gold-top SST tube at 0 minutes (Baseline), and 30, 60, 90, and 120 minutes after the Arginine infusion. (Minimum Whole Blood: 2.0 mL)

Rejection Criteria

• Plasma specimens.
• Grossly hemolyzed, lipemic or icteric specimens.
• Non-frozen specimens.
• Specimens not collected and processed as indicated. 

In-Lab Processing

Let each specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Transfer 1.0 mL serum to a plastic aliquot tube and freeze (-20°C/-4°F or below) immediately. (Minimum Serum: 0.5 mL per specimen)

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers^® with Separator Gels
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers^® without Separator Gels
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 8 hours
Frozen (-20°C/-4°F or below): 2 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak Special Testing Laboratory

Performed

Stimulation Tests are performed by the Medical Short Stay Unit. Contact 248-551-5490, option 2, to schedule an appointment.

Reference Range

Normal baseline: Less than 3.7 ng/mL.
Normal response: Following an arginine infusion, serum HGH levels should rise to a value greater than 5.7 ng/mL.

Test Methodology

An indwelling intravenous line is maintained throughout the entire test for administering arginine and obtaining blood samples. A baseline HGH blood sample is drawn, an arginine infusion is administered and sequential serum HGH samples are drawn. The patient is assessed and monitored continuously. This test may be performed in sequence followed by an insulin tolerance test.

Interpretation

Contraindications:

Arginine stimulates the release of insulin and glucagon. Serum glucose usually remains normal but hypoglycemia can occur. Arginine should be given with caution to patients with severe hepatic or renal disease.

Clinical Utility

Stimulation tests are useful for the evaluation of a child with suspected growth hormone deficiency. They are also widely used to evaluate pituitary function and serve as indicators of destructive lesions of the pituitary or hypothalamus. Occasionally, these tests are used to evaluate the therapeutic response to treatment of acromegaly or gigantism. Simulation tests are often required because basal growth hormone is usually low. Its secretion can be stimulated physiologically or pharmacologically. Sleep or exercise tests are employed by some clinicians as screening tests for growth hormone deficiency. Definitive testing, however, is generally performed with pharmacologic agents. The most popular and reliable of these agents are insulin, arginine and L-dopa. Although all can elicit growth hormone increases in a majority of patients, a normal child may inexplicably fail to respond appropriately to any one of these tests. Therefore, an inadequate response to a single stimulation test cannot be considered diagnostic of growth hormone deficiency. At least two stimulation tests are recommended to confirm a diagnosis of growth hormone deficiency. The arginine infusion test is one option for assessment. It has been shown that a variety of amino acids given intravenously can stimulate growth hormone secretion. Arginine is the most commonly used of these preparations. Its mechanism of action is not entirely clear, but may involve adrenergic stimulation of the hypothalamus by circumventing the physiologic central nervous systems regulatory mechanisms in assessing end-organ function.

CPT Codes

80428
LOINC:  20637-5, 30062-4

Contacts

Last Updated

7/21/2024