25-hydroxyvitamin D, insulin-like growth factor-I, and bone mineral accrual during growth.
BACKGROUND
The extent to which 25-hydroxyvitamin D [25(OH)D] and IGF-I influence bone mineral content (BMC) accrual from early to mid-puberty is unclear. OBJECTIVE, SETTING, AND PARTICIPANTS: This study sought to determine relationships among 25(OH)D, IGF-I, and BMC in community-dwelling prepubertal females (n = 76; aged 4-8 yr at baseline) over a period of up to 9 yr.


METHODS
The hypothesis that changes in IGF-I vs. 25(OH)D are more strongly associated with BMC accrual was formulated after data collection. 25(OH)D and IGF-I were log-transformed and further adjusted using two-way ANOVA for differences in season and race. Linear mixed modeling (including a random subject-specific intercept and a random subject-specific slope on age) was employed to analyze the proportion of variance the transformed 25(OH)D and IGF-I variables explained for the bone outcomes.


RESULTS
IGF-I was more strongly associated with BMC accrual than 25(OH)D at the total body (R(2) = 0.874 vs. 0.809), proximal femur (R(2) = 0.847 vs. 0.771), radius (R(2) = 0.812 vs. 0.759), and lumbar spine (R(2) = 0.759 vs. 0.698). The rate of BMC accrual was positively associated with changes in IGF-I but negatively associated with 25(OH)D. When IGF-I and 25(OH)D were included in the same regression equation, 25(OH)D did not have a significant predictive effect on BMC accrual above and beyond that of IGF-I.


CONCLUSIONS
These prospective data in early adolescent females indicate that both 25(OH)D and IGF-I have a significant impact on bone mineral accrual; however, the positive association of IGF-I and BMC accrual is greater than the negative association of 25(OH)D and BMC accrual.
Department of Foods and Nutrition, The University of Georgia, Athens, Georgia 30602, USA.
M E
ME
Breen
E M
EM
Laing
D B
DB
Hall
D B
DB
Hausman
R G
RG
Taylor
C M
CM
Isales
K H
KH
Ding
N K
NK
Pollock
M W
MW
Hamrick
C A
CA
Baile
R D
RD
Lewis
D000704:Analysis of Variance; D001823:Body Composition; D015519:Bone Density / Q000502:physiology*; D002113:Calcification, Physiologic / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D004032:Diet; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D016014:Linear Models; D011446:Prospective Studies; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
D014807:Vitamin D; D007334:Insulin-Like Growth Factor I; C104450:25-hydroxyvitamin D