TG and congenital heart disease: The suppressed thyroid hormone levels in preterm infants could be attributed to several factors, including but not limited to immature hypothalamic-pituitary-thyroid regulation, loss of maternal thyroid hormone transfer in PTB, disease states in which cytokine elevation inhibiting the thyroid function, dopamine use for inotropic support, repeated iodine-based contrast computer-tomography use in infants with congenital heart diseases, and inadequate iodine intake postnatally (188, 189).