الفهرس 
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Abstract
Thyroid hormone plays an essential role in brain development in fetal and neonatal life, and hypothyroidism during this critical period of early life can lead to adverse neurodevelopmental sequelae. Patients with congenital heart disease (CHD) commonly receive large intravenous contrast loads during cardiac catheterization and undergo surgical procedures where topical iodine-containing antiseptics and dressings are frequently applied. Iodine is an essential micronutrient for thyroid hormone synthesis, and iodine can result in thyroid dysfunction with potential adverse neurocognitive sequelae in children, particularly in those <3 years of age in whom brain development is thyroid hormone-dependent. Aim of the work: The aim of the present study was to identify the effect of iodine exposure (either during cardiac catheterization as contrast media for imaging or antiseptic) on thyroid function in patients with CHD in pediatric age group and analyze the risk factors for development of hypothyroidism. Materials and Methods: Serum TSH and FT4 levels assay were done for 50child with CHD who underwent cardiac catheterization 24 hour before iodine exposure, 24hours, one week and two weeks after exposure .patients developed subclinical hypothyroidism (high serum TSH level above 4.5mI /L and normal FT4 levels), received thyroxin replacement therapy and was followed up for 6 months. Results: The incidence of hypothyroidism in the included children was 0% at admission, 5 cases (10%) at 24 hours after cardiac catheterization, 12 cases (24 %) at 1 week and 6 cases (12%) at 2 weeks. Those 6 cases received treatment and was followed up for 6 months. In the current study, patients with obstructive CHD showed higher frequency of hypothyroidism after cardiac catheter as compared with left to right shunt cases (p= 0.036). In this study, longer fluoroscopy time was significantly correlated to development of hypothyroidism following cardiac catheterization with cutoff point of 23.5 minutes. In the current study, with univariate regression analysis, Obstructive CHD cases, AS cases and iodine dose were shown as risk predictors for hypothyroidism. However, with multivariate regression analysis, iodine dose was shown as an independent risk factor for development of hypothyroidism. Conclusion: Children with CHD are vulnerable to development of hypothyroidism after exposure to iodine. Children with obstructive CHD who underwent cardiac catheterization with increased duration of fluoroscopy showed higher incidence for development of hypothyroidism.