1Lithuanian University of Health Sciences, Academy of Medicine, Faculty of Medicine
Congenital hypothyroidism is the most common cause of avoidable mental retardation in children. Congenital hypothyroidism can be caused by either a defect in the thyroid gland formation (dysgenesis) or by a defect in the synthesis of thyroid hormones (dyshormonogenesis). The disease is usually diagnosed during a neonatal screening by taking a dry blood spot sample of the newborn at the age of 3-5 days. However, in premature infants, due to the immaturity of the hypothalamic-pituitary-thyroid axis, a neonatal screening result may be false negative. For this reason, preterm infants should be tested twice: during the neonatal screening and two weeks after the birth. It is also important to differentiate congenital hypothyroidism from transient hypothyroxinemia of prematurity and from transient congenital hypothyroidism, as the tactics and duration of treatment depend on it.
Aim: to determine the etiology, symptomatic, epidemiology and diagnostics of congenital hypothyroidism, their differences between term and preterm infants.
Methods: a systematic review of the literature was performed using the PubMed medical database. Selected articles examining the etiology, symptomatic, epidemiology, and diagnosis of congenital hypothyroidism and their differences between preterm and preterm infants. English word combinations were used for search: congenital hypothyroidism, premature neonate, transient congenital hypothyroidism, transient hypothyroxinemia of prematurity.
Conclusions. Preterm infants should be tested twice for congenital hypothyroidism- during the neonatal screening and then additionally at the age of two weeks, thus avoiding false negative results. Also, when assessing preterm neonate’s T4 and TSH levels, it is necessary to consider medications given to the infant, neonate’s gestational age at birth, maternal illnesses and medications taken during pregnancy, in order to differentiate between transient hypothyroxinemia of prematurity and transient congenital hypothyroidism.
Keywords: congenital hypothyroidism, premature neonate, preterm infant, transient neonatal hypothyroidism, thyroid.