Treatment of iodine deficiency in school-age children increases insulin-like growth factor (IGF)-I and IGF binding protein-3 concentrations and improves somatic growth.
BACKGROUND
Iodine deficiency in utero impairs fetal growth, but the relationship between iodine deficiency and postnatal growth is less clear.


OBJECTIVE
The objective of the study was to determine whether iodine repletion improves somatic growth in iodine-deficient children and investigate the role of IGF-I and IGF binding protein (IGFBP)-3 in this effect.


METHODS
Three prospective, double-blind intervention studies were done: 1) in a 10-month study, severely iodine-deficient, 7- to 10-yr-old Moroccan children (n = 71) were provided iodized salt and compared with children not using iodized salt; 2) in a 6-month study, moderately iodine-deficient, 10- to 12-yr-old Albanian children (n = 310) were given 400 mg iodine as oral iodized oil or placebo; 3) in a 6-month study, mildly iodine-deficient 5- to 14-yr-old South African children (n = 188) were given two doses of 200 mg iodine as oral iodized oil or placebo. At baseline and follow-up, height, weight, urinary iodine (UI), total T4 (TT4), TSH, and IGF-I were measured; in Albania and South Africa, IGFBP-3 was also measured.


RESULTS
In all three studies, iodine treatment increased median UI to more than 100 microg/liter, whereas median UI in the controls remained unchanged. In South Africa, iodine repletion modestly increased IGF-I but did not have a significant effect on IGFBP-3, TT4, or growth. In Albania and Morocco, iodine repletion significantly increased TT4, IGF-I, IGFBP-3, weight-for-age z scores, and height-for-age z scores.


CONCLUSIONS
This is the first controlled study to clearly demonstrate that iodine repletion in school-age children increases IGF-I and IGFBP-3 concentrations and improves somatic growth.
Zimmermann
Michael B
MB
Laboratory for Human Nutrition, Swiss Federal Institute of Technology, LFV E19, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland. michael.zimmermann@ilw.agrl.ethz.ch
Jooste
Pieter L
PL
Mabapa
Ngoako Solomon
NS
Mbhenyane
Xikombiso
X
Schoeman
Serina
S
Biebinger
Ralf
R
Chaouki
Noureddine
N
Bozo
Maksim
M
Grimci
Lindita
L
Bridson
John
J
D000415:Albania; D002648:Child; D005260:Female; D006043:Goiter, Endemic / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism; D006130:Growth Disorders / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007455:Iodine / Q000008:administration & dosage* / Q000172:deficiency*; D008297:Male; D009018:Morocco; D010919:Placebos; D011446:Prospective Studies; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D013019:South Africa; D016896:Treatment Outcome
C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D010919:Placebos; D017673:Sodium Chloride, Dietary; C034024:iodized salt; D007334:Insulin-Like Growth Factor I; D007455:Iodine