Endocrine Abstracts

Insulin-like growth factor-1 (IGF-I) is a 70-amino acid peptide hormone which is the principal mediator of the effects of growth hormone (GH). Pituitary GH is secreted in a pulsatile manner and is subjected to various environmental and physiological stimuli. In contrast, IGF-I is synthesised in a more stable manner and has a longer half-life therefore it is a more reliable biomarker of GH status. Hence IGF-I measurements are essential for the diagnosis and treatment of GH deficiency and GH-excess conditions such as acromegaly. Traditionally, IGF-I has been measured by using commercial immunoassays but an alternative platform for serum IGF-I quantification is liquid-chromatography mass spectrometry (LC-MS). Nevertheless the mainstay for IGF-I analyses in the UK remains the use of automated immunoassays supplied from principally three manufacturers: Siemens Healthineers, DiaSorin and Immunodiagnostic Systems (IDS). Although a WHO international standard (IS) for IGF-I (IS 02/254) is available for the calibration of IGF-I immunoassays, there are still significant method related differences observed for IGF-I results. This short presentation will use clinical examples to highlight factors that contribute to IGF-I assay differences such as; the effect of insulin-like growth factor binding proteins (IGFBPs), the need for establishing appropriate reference values etc to demonstrate their impact on IGF-I result interpretation and patient care.