Newcastle Laboratories

Growth Hormone, serum

Clinical Background:

Growth hormone (GH) is a polypeptide hormone secreted by the anterior pituitary gland. Secretion is episodic and is associated with exercise, the onset of deep sleep prandial status and in response...

Growth hormone (GH) is a polypeptide hormone secreted by the anterior pituitary gland. Secretion is episodic and is associated with exercise, the onset of deep sleep prandial status and in response to low glucose levels. Synthesis and release is under the control of hypothalamic releasing peptides and inhibitory peptides such as somatostatin. Insulin-like growth factor (IGF-1) exerts an inhibitory effect through negative feedback mechanisms. Circulating GH consists of several molecular isoforms, with 22000 Dalton GH being the most abundant, followed by a 20000 Dalton GH variant. GH is physiologically important in 2 main areas. Firstly, it has an integral role in skeletal growth which is demonstrated in either excess or deficiency in childhood. The action of GH in part is mediated through IGF-1 as well as promoting protein synthesis and the uptake of amino acids into cells. Secondly, GH influences intermediary metabolism by stimulating lypolysis and is antagonistic to the insulin mediated uptake of glucose. GH secretion is stimulated by hypoglycaemia, and suppressed by hyperglycaemia.

GH is commonly measured in the investigation of GH excess or insufficiency. Random samples may be of limited diagnostic utility due to the episodic nature of GH secretion. Diagnosis or exclusion of GH deficiency or excess often requires measurement of GH response to dynamic function testing, for example the oral glucose tolerance test in investigation of GH excess or stimulation tests in investigation of GH insufficiency.

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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

  • Sample Stability:

    Unseparated: Same day
    Separated: 7 days at 4-8°C, 2 months at -20°C

    Unseparated: Same day
    Separated: 7 days at 4-8°C, 2 months at -20°C

  • Transport Requirements:

    Ambient

    Ambient

  • Interpretation:

    Provision of diagnostic cut-offs for GH during dynamic function testing is difficult due to a lack of normative data that are age, gender and BMI adjusted and also due to variability between GH ass...

    Provision of diagnostic cut-offs for GH during dynamic function testing is difficult due to a lack of normative data that are age, gender and BMI adjusted and also due to variability between GH assays. The following recommendations are made in the Endocrine Society Clinical Practice Guidelines:

    Investigation of acromegaly:

    Single random GH measurements are not recommended for diagnosis due to inherent episodic GH secretion from normal and adenomatous pituitary glands. A nadir serum GH concentration <1 µg/L within 2 hours of 75g oral glucose load usually excludes acromegaly. Increasing age and elevated BMI may be associated with abnormal post-glucose GH suppression.

    Investigation of growth hormone insufficiency:

    According to a multi-centre study cut-offs of 5.1 µg/L for the insulin tolerance test and 4.1 µg/L for the GHRH-arginine tests had sufficient specificity and sensitivity for the diagnosis of adult growth hormone deficiency. However, the appropriate cut-offs are related to BMI, with lower cut-offs required for those with higher BMIs compared to those with lower.

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  • Reference Ranges:

    No reference ranges are provided due to the pulsatile nature of growth hormone secretion.

    No reference ranges are provided due to the pulsatile nature of growth hormone secretion.

  • 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:

    Lithium Heparin anticoagulated samples are acceptable

    Lithium Heparin anticoagulated samples are 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

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

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