Reference ranges for an automated chemiluminescent assay for serum insulin-like growth factor I (IGF-I) in a large population of healthy adults from Buenos Aires.
OBJECTIVE
Insulin-like growth factor I (IGF-I) represents an essential tool in the diagnostic work-up and in the monitoring of treatment efficacy for somatotrophic axis disorders both in children and adults. A large number of factors including, but not limited to, age, sex and weight as well as analytical variables influence IGF-I serum levels; therefore, reliable normative data are essential for a correct interpretation of results. The aim of the present study was to establish reference range values for serum IGF-I, in a large population of healthy adults from Buenos Aires city.


METHODS
The study included serum samples from 1044 healthy subjects aged 21-87 years (423 females and 621 males) divided into groups by sex at 5-year intervals from 21 to >75 years. Serum IGF-I concentrations were determined by a fully automated two-site, solid-phase, enzyme-labeled chemiluminescent immunometric assay (Immulite 2000, Siemens Healthcare Diagnostics). IGF-BP interferences are circumvented by blocking IGF-BP binding sites with excess IGF-II in the on-board predilution step.


RESULTS
Results show the age dependence of circulating IGF-I levels, with a smooth and steady decrease in levels with age. No sex differences were found in subjects >26 years; however, in the group aged 21-25 years, IGF-I levels were significantly higher in females. In conclusion, this study provides age- and gender-adjusted normal reference ranges for IGF-I levels obtained with an automated immunometric chemiluminescent assay Immulite 2000 in healthy adult subjects.
División Endocrinología, Hospital Carlos G Durand, Buenos Aires, Argentina.
M
M
Guitelman
F
F
Smithuis
N
N
Garcia Basavilbaso
C
C
Aranda
B
B
Fabre
A
A
Oneto
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001118:Argentina; D005260:Female; D006130:Growth Disorders / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008163:Luminescent Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012737:Sex Factors; D055815:Young Adult
D007334:Insulin-Like Growth Factor I