IGF-I - serum

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Specimen: 5 mL blood in a plain tube.

Method: Immunoassay.

Reference Interval: Varies with age, gender and pubertal status. Adult: 13-50 nmol/L.

Application: Diagnosis of acromegaly or gigantism. Diagnosis of Laron dwarfism. Limited value in the assessment of growth hormone deficiency or nutritional status.

Interpretation: Levels are increased in acromegaly, and the test is used in the initial assessment of patients, prior to a growth hormone suppression test. Its diagnostic value is limited at the time of puberty and in malnutrition and severe illness. In Laron dwarfism, a rare disease, growth hormone is not reduced but IGF-I is reduced. Low IGF-I has been used as a test for protein malnutrition, but interpretation is difficult in view of changes in plasma IGF-binding proteins.

Reference: Le Roith D et al. Ann Intern Med 1992; 116: 854-862.

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