TG and cyclic hematopoiesis: Several studies have highlighted the elevated risk of CH in preterm infants due to their increased survival rates [8] and their unique and dynamic pattern of thyroid hormone levels, explained by the immaturity of the hypothalamic–pituitary–thyroid (HPT) axis; the withdrawal of maternal thyroxine (T4) after birth, exposure to iodine especially in iodine deficient areas; medications; birth weight, and the persistence of fetal metabolism [22].