[Measurement IGF-I in human blood by immunoenzymometric assay].
Insulin-like growth factor-I (IGF-I) is the growth factor which binds to its specific binding proteins in plasma and mediates most of the actions of growth hormone (GH). In terms of this, measurement of IGF-I concentrations is considered to be important in the diagnosis and treatment of growth abnormalities. In the present report we describe a modified immunoenzymometric assay (IEMA) for IGF-I using monoclonal antibody and peroxidase conjugated polyclonal antibody, which was originally developed by Tamura et al. The minimum detection level was 3ng/ml and good linearity was obtained at a range of 3-50ng/ml. The recovery of added IGF-I was nearly quantitative, and cross reaction with human IGF-II was less than 1%. There was a significant positive correlation between the IGF-I values determined by IEMA and by RIA. We measured the levels of IGF-I by this IEMA in normal subjects and children with short stature. Serum or plasma samples were extracted by acid-ethanol method. In normal children IGF-I level was observed age-dependently. IGF-I values gradually increased and reached peak levels (101.2-473.2ng/ml) in pubertal period and thereafter decreased to adult levels (67.3-329.6ng/ml). In subjects with short stature older than 5 yrs, the percentages falling below the normal mean for chronological age by at least 2SD were 100% for complete GH deficiency (n = 5), 80.0% for partial GH deficiency (n = 15), 25.0% for GH neurosecretory dysfunction (n = 4), 40.0% for non-endocrine short stature (n = 60) and 25.0% for Turner syndrome (n = 4). In children younger than 4 yrs, it may be difficult to use IGF-I for diagnosis of GH deficiency because there was an overlap in IGF-I values with normal children. IEMA for IGF-I is shown to be a reliable method for measurement of IGF-I in blood and is appropriate for diagnosis of growth disorders with short stature in subjects older than 5 yrs.
Segawa
M
M
First Department of Internal Medicine, School of Medicine, Toho University.
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000911:Antibodies, Monoclonal; D002648:Child; D002675:Child, Preschool; D005260:Female; D006130:Growth Disorders / Q000097:blood / Q000175:diagnosis; D006801:Humans; D007124:Immunoenzyme Techniques; D007223:Infant; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D012016:Reference Values
D000911:Antibodies, Monoclonal; D007334:Insulin-Like Growth Factor I