Serum concentrations of insulin, insulin-like growth factor-I and insulin-like growth factor binding proteins are different between white and African American girls.
OBJECTIVE
To determine whether serum insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP) concentrations are different between African American and white girls.


METHODS
Serum glucose and hormone concentrations were measured in blood samples collected after a 12-hour fast from 79 white and 57 African American healthy girls between 9 and 17 years of age. Tanner stages of pubic hair development were evaluated by physical examination, and body composition by dual energy x-ray absorptiometry.


RESULTS
The African American girls were older and sexually more mature and had higher fat mass, higher serum insulin and free IGF-I concentrations, higher serum free IGF-I to total IGF-I ratio, but lower serum IGFBP-1 concentrations than the white girls. After controlling for sexual maturation and fat mass, the serum concentrations of total IGF-I, bound IGF-I, and IGFBP-3 in the white girls became significantly higher than those in the African American girls. The higher concentrations of total IGF-I in the white girls were due to a proportional increase in the concentrations of bound IGF-I that coincided with a similar increase in serum IGFBP-3 concentrations.


CONCLUSIONS
Higher serum insulin concentrations in the African American girls are associated with lower serum IGFBP-1 concentrations and increased bioavailability of free IGF-I, which may contribute to their accelerated growth compared with their white counterparts.
Wong
W W
WW
US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Houston, Texas 77030, USA.
Copeland
K C
KC
Hergenroeder
A C
AC
Hill
R B
RB
Stuff
J E
JE
Ellis
K J
KJ
D015502:Absorptiometry, Photon; D000293:Adolescent; D000704:Analysis of Variance; D001682:Biological Availability; D044383:Black People / Q000235:genetics*; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition / Q000235:genetics / Q000502:physiology; D002648:Child; D005260:Female; D006128:Growth / Q000235:genetics / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000235:genetics*; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood* / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism*; D010808:Physical Examination; D011627:Puberty / Q000235:genetics / Q000502:physiology; D044465:White People / Q000235:genetics*; D001741:Black or African American
D001786:Blood Glucose; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I