EFFECTS OF IODINE DEFICIENCY ON INSULIN-LIKE GROWTH-FACTOR-I, INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-3 LEVELS AND HEIGHT ATTAINMENT IN MALNOURISHED CHILDREN

OBJECTIVE The expression and synthesis of IGF-1 and IGFBP-3 have been shown to be regulated by hormones and nutrition. We study the effects of malnutrition and iodine deficiency on these growth factors and the height attainment of a group of children. DESIGN We measured serum IGF -1 and IGFBP-3 levels in a group of Malaysian aborigine children from three jungle settlements; Sinderut and Pos Lanai are known for iodine deficiency and endemic goitre, and Gombak is an iodine replete area wi th better socioeconomic status. PATIENTS A total of 246 children were studied, 188 in the age group 4-10 years and 88 in the age group 11-15 years. MEASUREMENTS All children were assessed anthropometrically and height standard deviation score (SDS) were calculated using the CDC A nthropometric Software package. Malnutrition was confirmed clinically and according to the WHO definition of malnutrition. IGF-1 and IGFBP-3 were determined by radioimmunoassay, and T4 and TSH by immunoradiomet ric assay. RESULTS Based on the height SDS, Sinderut and Pos Lanai chi ldren were significantly more malnourished and stunted than the Gombak children (P = 0.0001). T4 levels were significantly lower (P = 0.0001 ) amongst the 4-10-years old Sinderut (81 +/- 2 nmol/l) than in Pos La nai (101 +/- 3 nmol/l) or Gombak (123 +/- 3 nmol/l) children. Similar findings were also seen in the older children; mean T4 levels of those from Sinderut and Pos Lanai (83 +/- 3 and 88 +/- 4 nmol/l respectivel y), were low (P = 0.0001) compared to Gombak (118 +/- 3 nmol/l). Conve rsely, TSH levels in both age groups of Sinderut children were signifi cantly elevated (P = 0.0001) (3.5 +/- 0.2 and 3.9 +/- 0.3 mU/l respect ively) compared to age-matched groups from Pos Lanai (2.1 +/- 0.1 and 2.2 +/- 0.2 mU/l respectively) and Gombak (1.5 +/- 0.1 and 1.5 +/- 0.2 mU/l respectively). IGF-1 and IGFBP-3 correlated significantly with t he height SDS of the children, in both the 4-10 (r = 0.400, P = 0.0001 and r = 0.365, P = 0.0001 respectively) and 11-15 years age groups (r = 0.324, P = 0.002 and r = 0.533, P = 0.0001 respectively). Correlati on between IGFBP-3 and T4 levels was more significant in the younger c hildren (r = 0.412, P = 0.0001). Association between IGF-1 and T4 leve ls was significant only in the 4-10 years age group (r = 0.237, P = 0. 001).CONCLUSIONS Varying duration and degree of exposure to malnutriti on and iodine deficiency resulted in different mean levels of T4, TSH, IGF-1 and IGFBP-3 in the three areas. The strong positive association s between IGF-1 and IGFBP-3 levels and height SDS suggest that these b iochemical measurements are indeed useful indicators of growth and nut ritional status in children. The significant correlations between T4 a nd IGFBP-3 and IGF-1 suggests the importance of thyroid hormones in re gulating the synthesis of these growth factors. The age-related increa se of these growth factors even amongst malnourished, iodine deficient children implies that age-matched reference ranges are essential for proper evaluation of laboratory results.