Serum insulin-like growth factor-I adult reference values for an automated chemiluminescence immunoassay system

Analysis of insulin-like growth factor I (IGF-I) in serum is fundamental in order to aid in the diagnosis of growth hormone (GH)-related disorders, as well as in the diagnosis and follow-up of other diseases. Considering the importance of IGF-I local normal range, the aim of this study was to determine reference values for IGF-I (Immulite 2000) in a Brazilian adult population from the city of Rio de Janeiro. This study included samples of blood taken from 484 healthy subjects (251 men, 233 women) aged 18 to 70. The subjects agreed with this study, approved by the ethical committee of the Instituto Estadual de Hematologia Arthur de Siqueira Cavalcanti, Rio de Janeiro, Brazil. The samples were analyzed by an automated immunochemiluminometric assay (ICMA). For data analysis, age and sex-specific figures were fitted after transformation of IGF-I values. In adulthood, a slow age-dependent decrease was seen. IGF-I in women were significantly higher than in men. The present study established age-and sex-specific IGF-I reference values, for the healthy Brazilian adult populatoin from the city of Rio de Janeiro, determined with the currently most widely IGF-I assay used in Brazil (Immulite 2000).