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Somatomedin-C Blood Level (Insulin Like Growth Factor 1, Serum)

Somatomedin-C, Sm-C, IGF-1

Test Codes

EPIC: LAB3535, SOFT: IGF1, Antrim #19581

Department

Immunology

Specimen Collection Criteria

Collect: One Gold-top SST tube. (Minimum Whole Blood: 2.0 mL)

Send specimen to the Laboratory for processing immediately after collection. 

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube immediately. (Minimum Serum: 0.5 mL)

Preparation for Courier Transport

Transport: Centrifuged collection tube, refrigerated (2-8°C or 36-46°F). (Minimum Serum: 0.5 mL)

Rejection Criteria

• Plasma specimens. 
• Severely lipemic, icteric, or grossly hemolyzed specimens. 
• Specimens not collected and processed as indicated. 

In-Lab Processing

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

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers^® with Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
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): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 1 year

Specimen Storage in Department Prior to Disposal:

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

Laboratory

Royal Oak Special Testing Laboratory

Performed

Monday – Friday.
Results available within 2 business days.

Reference Range

Pediatric Reference Ranges (Central 95% Range)

Age (Years)	Male (ng/mL)	Female (ng/mL)
0-3	<15-129	18-172
4-6	22-208	35-232
7-9	40-255	57-277
10-11	69-316	118-448
12-13	143-506	170-527
14-15	177-507	191-496
16-18	173-414	190-429

Adult Reference Ranges

Age (Years)	Central 95% Range (ng/mL)
19-21	117-323
22-24	99-289
25-29	84-259
30-34	71-234
35-39	63-223
40-44	58-219
45-49	53-215
50-54	48-209
55-59	45-210
60-64	43-220
65-69	40-225
70-79	35-216
80-90	31-208

Tanner Stage Reference (Central 95% Range ng/mL)

Tanner Stage	Male	Female
1	63-271	71-394
2	114-411	122-508
3	166-510	164-545
4	170-456	174-480
5	161-384	169-400

 

 

Test Methodology

Siemens Imulite 2000 XPI platform.
Chemiluminescent Immunoassay.

Interpretation

Insulin like growth factor (IGF-1) is regulated by human growth hormone (GH) and nutritional intake. Much of the GH dependent, growth promoting activity in serum is due to IGF-1. The liver is the major source of IGF-1 in blood. The anabolic and growth promoting effects mediated by the IGFs include cell proliferation and protein synthesis. Plasma IGF-1 concentrations are relatively stable making them a reliable indicator of GH output. GH levels vary considerably and often require provocative testing to interpret.

Consistently low IGF-1 levels are seen in children with GH deficiency (hypopituitarism) and rise with GH injections. Generally, normal IGF-1 levels in a short child is strong evidence against the diagnosis of GH deficiency, particularly when the patient is 5-6 years old, a time at which abnormally low values can be discriminated from normal. Serum levels may be low in GH-deficient children who have a craniopharyngioma. A normal level suggests that GH deficiency is not present, however a low value in a growth-retarded child is not diagnostic of hypopituitarism.

Undernutrition is associated with low IGF-1 levels in children.

Elevated serum IGF-1 concentrations are seen in patients with acromegaly and in children with gigantism due to excess of pituitary GH. Elevated IGF-1 serum values in pubertal patients should be interpreted carefully because levels are normally increased at this time and may be as much as 4-5 times adult concentration. IGF-1 levels are also elevated during pregnancy.

Clinical Utility

Aids in evaluation of growth disorders. Decreased IGF-1 levels are also associated with malnutrition.

CPT Codes

84305
LOINC:  30 Minutes 47663-0, 1-Hour 47657-2, 2-Hour 47659-8, 3-Hour 47662-2, 4-Hour 29378-7, 5-Hour 27852-3

Contacts

Last Updated

11/1/2024