Insulin-like Growth Factor I (IGF-I)

Clinical use
1 Diagnosis and monitoring treatment of acromegaly.

When measured in a random sample, serum insulin-like growth factor I (IGF-I) concentration correlates more closely with disease status than does serum growth hormone concentration.

2 Investigation of short stature in children.

Measurement of IGF-I in conjunction with the assay of growth hormone during a stimulation test, may assist in establishing the cause of retarded growth.

3 Differential diagnosis of spontaneous hypoglycaemia.

When suppressed concentrations of insulin, C-peptide, ketone and GH are associated with severe hypoglycaemia, the measurement of IGF-I and IGF-II is indicated. An elevated IGF-II to IGF-I molar ratio is consistent with the diagnosis of a non-islet cell tumour.

Patient preparation
1,2 Investigation of acromegaly and short stature.

Collect blood (10 mL) into a plain vacutainer or syringe.

3 Differential diagnosis of spontaneous hypoglycaemia.

Collect blood (10 mL) during a hypoglycaemic episode (see Insulin and C-peptide).

Sample preparation
Transfer the blood to a plain tube and allow to clot. Separate the serum promptly and store at -200C.

1, 2 Investigation of acromegaly and short stature.

Send serum (2 mL) to the SAS laboratory. Record on the SAS request form the following details: age and sex; clinical information on evidence of hypothyroidism; diabetes; nutritional status; liver function; details of current treatment.

3 Differential diagnosis of spontaneous hypoglycaemia.

Send the frozen serum (5 mL) to the SAS laboratory, (see Insulin and C-peptide, page 75). Ensure the sample remains frozen during transport.

Serum amples for IGF-1 alone (Birmingham, radioimmunoassay) can be sent by first class post.

Reference range
Where details of the patients age and gender are provided the relevant reference will be quoted with the results.

Centres offering this assay
Birmingham University Hospital Endocrine Laboratory
Guildford RSH Peptide Hormone Laboratory
Newcastle Royal Infirmary Endocrine Laboratory

Beastall GH. Insulin-like Growth Factor-1: assay and clinical significance. Proc. UK NEQAS meeting 1994; 1: 144-8.

Hindmarsh PC, Brook CGD. Short stature and growth hormone deficiency. Clin Endocrinol (Oxf) 1995; 43: 133-42.

Shakespear RA, Lynch SS, Rudd BT, Williams JW, White DA. Serum IGF-1 assays: which sample preparation method? Proceedings of the ACB National Meeting 1993; C11.

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