Newcastle Laboratories

Insulin-like growth factor 1, serum

Clinical Background:

IGF-1 is a 70 amino acid straight chain peptide of molecular weight 7649 Daltons. It is part of a family of growth factors which include IGF-1 and IGF-2 . IGF-1 is highly basic in nature and circul...

IGF-1 is a 70 amino acid straight chain peptide of molecular weight 7649 Daltons. It is part of a family of growth factors which include IGF-1 and IGF-2 . IGF-1 is highly basic in nature and circulates bound to high molecular weight IGF-binding proteins (IGFBP-1 to -6), which help to modulate IGF-1 action. IGF-1 mediates the growth promoting action of growth hormone (GH), being released from a variety of body tissues (predominantly the liver) in response to GH. <br /> IGF-1 is used as an index of GH secretion in the diagnosis of GH-deficiency and excess, as well as monitoring of treatment of these disorders. The half-life of IGF-1 is approximately 15 hours and so is not affected by short-term variation in GH secretion. IGF-1 is recommended as an initial screening test for acromegaly but has limitations as a standalone diagnostic test, particularly in the diagnosis of growth hormone deficiency and dynamic function tests are often required to confirm or exclude GH deficiency/excess. Other than GH, the most important factors influencing IGF-1 concentration are age and gender. Peak levels occur during adolescence and are lowest at birth. It is therefore important to use gender and age related reference ranges

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Test Documents

Test Details

  • Discipline:

    Biochemistry

    Biochemistry

  • Specimen Container Adult:

    serum/lithium heparin plasma/EDTA plasma

    serum/lithium heparin plasma/EDTA plasma

  • Specimen Container Paediatric:

    serum/lithium heparin plasma/EDTA plasma

    serum/lithium heparin plasma/EDTA plasma

  • Minimum Volume Adult:

    2 mL blood

    2 mL blood

  • Minimum Volume Paediatric:

    1 mL blood

    1 mL blood

  • Special Requirement:

    If samples are not to be despatched within 24 hours, suggest store at -20°C.

    If samples are not to be despatched within 24 hours, suggest store at -20°C.

  • Sample Stability:

    Unseparated: Same day (ideally separate within 2 hours)
    Separated: 3 days at 20-25°C, 3 days at 2-8°C, 1 month at -20°C

    Unseparated: Same day (ideally separate within 2 hours)
    Separated: 3 days at 20-25°C, 3 days at 2-8°C, 1 month at -20°C

  • Transport Requirements:

    Ambient

    Ambient

  • Interpretation:

    The majority of patients with acromegaly have a raised serum IGF-1 concentration (when appropriate age-related reference ranges are used). However, false positives can occur particularly in pregnan...

    The majority of patients with acromegaly have a raised serum IGF-1 concentration (when appropriate age-related reference ranges are used). However, false positives can occur particularly in pregnancy and late adolescence. Importantly IGF-1 concentrations may be affected by hepatic or renal failure, hypothyroidism, malnutrition, severe infection and poorly controlled diabetes. Confirmation of a biochemical diagnosis of growth hormone excess requires measurement of GH in response to the oral glucose tolerance test. Measurement of IGF-1 also has a role in monitoring patients treated for acromegaly with normalised IGF-1 concentrations often one of the treatment goals.

    Although a low IGF-1 (in the absence of factors such as liver disease, poorly controlled diabetes) provides evidence of growth hormone deficiency, an IGF-1 concentration within the reference range cannot be used to exclude the diagnosis. GH measurement during dynamic function testing is usually required to diagnose/exclude growth hormone deficiency.

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  • Reference Ranges:

    Detailed age-related reference ranges are available. Relevant ranges will be included with reports.

    An IGF-1 SD-score spreadsheet is available, which can be used to calculate age/gender specific SD...

    Detailed age-related reference ranges are available. Relevant ranges will be included with reports.

    An IGF-1 SD-score spreadsheet is available, which can be used to calculate age/gender specific SD-scores and percentiles. (here)

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  • Factors Affecting Result:

    Gross haemolysis, lipaemia or icterus may interfere.
    Heterophilic antibodies can interfere with immunoassays.

    Gross haemolysis, lipaemia or icterus may interfere.
    Heterophilic antibodies can interfere with immunoassays.

  • Other Info:

    EDTA and Lithium heparin anticoagulated sampes are also acceptable.

    EDTA and Lithium heparin anticoagulated sampes are also acceptable.

  • Routine Contact Name:

    Duty Biochemist

  • Routine Telephone:

    Freeman: 0191 244 8889

    RVI: 0191 282 9719

    Freeman: 0191 244 8889

    RVI: 0191 282 9719

  • Routine Email:

  • Specialist Test:

    Yes

    Yes

  • Specialist Contact Name:

    Endocrine Lab

    Endocrine Lab

  • Specialist Telephone:

    0191 282 4025

    0191 282 4025

Availability:

Assayed Twice weekly

Site of analysis: RVI

Turn Around:

Within 2 weeks.

Send To:

Department of Blood Sciences – RVI

Level 3
Leazes Wing
Royal Victoria Infirmary
Queen Victoria Road
Newcastle upon Tyne
NE1 4LP

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