Pathology tests database

Sample and container requirements

Serum

Minimum volume required

300 µL serum

Special requirements

None

Patient preparation

For a single random sample, fast the patient overnight and collect the blood sample while the patient is resting and unstressed. For dynamic function tests the patient should be fasted overnight and sampling commence between 9am and 10am. Repetitive sampling should be via an indwelling venous catheter inserted 30 minutes before the commencement of the test. Dynamic function tests may be dangerous and should always be carried out under medical supervision. The assay is affected by pegvisomant (a highly selective GH receptor antagonist) and is therefore not suitable for patients under pegvisomant treatment. There is no interference with Octreotide (somatostatin analogue) or Cabergoline (dopamine agonist). The assay is not suitable for the determination of GH in samples from pregnant women. This is due to cross-reactivity to placental hGH. Placental GH is a variant of pituitary hGH36 and its serum levels increase during the course of pregnancy. Samples from patients receiving high biotin doses (i.e. >5 mg/day) should be taken at least 8 hours post-dose. In rare cases, interference due to extremely high titres of antibodies to analyte‑specific antibodies, streptavidin or ruthenium can occur. These effects are minimized by suitable test design.

Sample viability

Turnaround time

7 days

Reference range

No reference range for growth hormone is quoted, as levels can depend upon the time of day, medication and exercise.

Clinical guidance

Please refer to LabTestsOnlineUK to learn more about growth hormone. https://labtestsonline.org.uk/tests/growth-hormone

Notes

GH secretion is pulsatile and random samples are of little diagnostic value. IGF-1 can be used to investigate for GH deficiency. GH testing is usually provocative, using either a GH stimulation test or a GH suppression test to track GH levels over time. A series of specimens for GH may also be sent, as part of a “Dynamic function test” (DFT), for investigation of GH excess or deficiency.