Normal values of serum IGF-1 in adults: results from a Brazilian population

Objective: To determine the normal values of serum IGF-1 (Immulite 2000) in a Brazilian adult (21-70 years) population. Subjects and methods: Healthy volunteers were divided into 10 groups according to age (5-year intervals), with 100 subjects (50 men and 50 women) per group. One-hundred participants were selected for repetition of the test after 12 weeks. Results: No difference in IGF-1 values was observed between men and women, but a progressive reduction of serum IGF-1 with age was seen. The reference values provided by the manufacturer of the assay, although discretely higher, were very close to the values found in this study. A second measurement of IGF-1 after 12 weeks revealed a variation <= 20% in 99% of subjects. Conclusions: This study established the reference range for IGF-1 determined with the Immulite 2000 assay for a large number of healthy Brazilian adults stratified according to age, and suggests that variations > 20% in IGF-1 levels within an interval of 12 weeks cannot be attributed to inter-assay variability. Arq Bras Endocrinol Metab. 2010,54(5).477-81