Evolution of congenital hypothyroidism in a cohort of preterm born children

Abstract

Background: Congenital hypothyroidism (CH) is reported to be more common in preterm infants than in term infants, especially in sick preterm infants. Though a frequent possibility of transitory thyroidal alterations in this category of neonates, the evolution of CH to transient or permanent forms is unpredictable.

Methods: We retrospectively analyzed medical records of 28 preterm infants (<37 weeks gestation) who had exhibited a positive screening for CH at birth during the period 2000-2015 followed in our Center. Children were divided into three groups: permanent CH (PCH) with thyroid dysgenesis, PCH with eutopic normal-sized thyroid gland, and transient CH (TCH) with eutopic normal-sized thyroid gland. In all groups we described clinical and biochemical characteristics. Secondly, we analyzed the differences between patients with thyroid dysgenesis and patients with eutopic normal-sized gland and we compared PCH and TCH groups with normal-sized thyroid gland in order to identify clinical or biochemical data for early detection of transient forms.

Results: Of all patients, 21.4% showed thyroid dysgenesis while 78.6% presented eutopic normal-sized gland. Infants with thyroid dysgenesis had higher median (IQR) baseline s-TSH and levothyroxine (L-T4) dose per weight at 12 months (12 m-dose) than patients with eutopic normal-sized gland. At re-evaluation of the patients with eutopic normal-sized gland, 36% showed PCH and 64% had TCH. The age of the patients at the beginning of L-T4 treatment, gestational age (GA), birth weight, blood thyroid stimulating hormone levels (b-TSH) at first newborn screening (NBS), baseline serum thyroid stimulating hormone (s-TSH), and L-T4 12 m-dose were statistically different between the two groups.

Conclusions: Our results demonstrate that factors as GA, birth weight, b-TSH levels at first NBS, baseline s-TSH, L-T4 12 m-dose and age at the start of the treatment may be considered useful predictive elements for the evolution of CH.

Keywords: congenital hypothyroidism; prematurity; re-evaluation.