Serum insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 levels in severe iodine deficiency

Iodine deficiency is an important public health problem worldwide. It is well known that it has severe consequences such as brain damage, developmental delay, deficits in hearing and learning and lower intellectual attainment. It also has a negative impact on growth. In this study, we aimed to address this issue and we assessed height standard deviation scores of children living in an area of severe iodine deficiency in comparison to those living in a mild iodine deficiency area. Serum levels of insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), thyroxine (T₄), and thyroid stimulating hormone (TSH) were also analyzed to investigate the mechanisms by which iodine depletion leads to growth failure. Pubertal children in a severe iodine deficient SID area had lower height standard deviation scores (HSDS), IGF-I and IGFBP-3 levels than those living in mild iodine deficient MID area. Similar findings could not be elucidated in the prepubertal age group. The major determinants of HSDS were age, IGF-I, IGFBP-3 and TSH. IGF-I and IGFBP-3 were negatively correlated with T₄. These findings suggest that iodine deficiency has a negative impact on growth, as well as IGF-I and IGFBP-3 levels. This effect seems to be due to the derangements in thyroid hormone economy arising from iodine depletion. The degree of this impact may be related to the duration of iodine depletion or may be dependent on the developmental stage of the organism at the time of iodine depletion.