Race/ethnic variation in serum levels of IGF-I and IGFBP-3 in US adults.
OBJECTIVE
The IGF axis plays a significant role in normal growth and development and variation in IGFs is associated with health outcomes. Past studies report variation in IGF levels among race/ethnic groups known to differ in disease incidence. This paper reports on race/ethnic variation in serum levels of IGF-I and IGF-BP3 in a nationally representative and ethnically diverse sample of US adults.


METHODS
Serum IGF-I and IGFBP-3 levels from the fasting subsample (n = 6061) of respondents to the US National Health and Nutrition Examination Survey III (NHANES III) were analyzed using an IGF-I ELISA (Diagnostic Systems Laboratory (DSL) 10-5600) and an IGFBP-3 IRMA (DSL 6600). The NHANES is a combined examination and interview survey of a nationally representative sample of US adults. Regression analyses were used to estimate cross-sectional associations between the IGF axis and demographic variables.


RESULTS
In unadjusted analyses, serum IGF-I levels were higher in males than in females, and IGFBP-3 levels were higher in females than in males. Both analytes were lower in older adults. Univariate analyses indicate that serum levels of IGF-I are lower in female Non-Hispanic Whites (NHW) (256 [4.9]) and Hispanics (249 [6.6]) than in Non-Hispanic Blacks (NHB) (281 [4.9]). However, in males, IGF levels in NHWs (287 [3.6]) and NHBs (284 [4.3]) are similar and levels in Mexican-Americans are only moderately reduced (265 [3.4]). Notably, NHB's have the highest molar ratio of IGF-I:IGFBP-3 at all ages. After adjustment for age and BMI, gender and race/ethnicity differences persist.


CONCLUSIONS
These cross-sectional data support exploration of the IGF axis as an explanation for some race/ethnic differences in cancer incidence.
Berrigan
David
D
Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Executive Plaza North MSC 7344, Bethesda, MD 20892-7344, USA. berrigad@mail.nih.gov
Potischman
Nancy
N
Dodd
Kevin W
KW
Hursting
Stephen D
SD
Lavigne
Jackie
J
Barrett
J Carl
JC
Ballard-Barbash
Rachel
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D016208:Databases, Factual; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D044469:Racial Groups; D012737:Sex Factors; D014481:United States; D055815:Young Adult
D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I