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

• Published in: The journal of clinical endocrinology and metabolism 2007-02, Vol.92 (2), p.437-442
• Main Authors: Zimmermann, Michael B., Jooste, Pieter L., Mabapa, Ngoako Solomon, Mbhenyane, Xikombiso, Schoeman, Serina, Biebinger, Ralf, Chaouki, Noureddine, Bozo, Maksim, Grimci, Lindita, Bridson, John
• Format: Article
• Language: English
• Subjects: Albania; Biological and medical sciences; Child; Endocrinopathies; Female; Fundamental and applied biological sciences. Psychology; Goiter, Endemic - complications; Goiter, Endemic - drug therapy; Goiter, Endemic - metabolism; Growth Disorders - drug therapy; Growth Disorders - etiology; Growth Disorders - metabolism; Humans; Insulin-Like Growth Factor Binding Protein 3; Insulin-Like Growth Factor Binding Proteins - blood; Insulin-Like Growth Factor I - metabolism; Iodine - administration & dosage; Iodine - deficiency; Male; Medical sciences; Morocco; Placebos; Prospective Studies; Sodium Chloride, Dietary - administration & dosage; South Africa; Treatment Outcome; Vertebrates: endocrinology
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2006-1901

Context: 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. Design, Participants, and Interventions: 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 μg/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. Conclusion: 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.