Congenital hypothyroidism in preterm infants: a 3- to 8-year longitudinal study in southern Thailand

Follow-up study of preterm infants with thyroid dysfunction after medication

OBJECTIVES

To study the effect of levothyroxine sodium tablets on the growth and development and thyroid function in preterm infants with thyroid dysfunction.

METHODS

A retrospective analysis was performed for 82 preterm infants who were born in the Department of Obstetrics of the First People's Hospital of Yunnan Province, from January 1, 2013 to December 31, 2017, and these infants were hospitalized after birth in the Department of Neonatology of the hospital. They were regularly followed up to observe growth and development and thyroid function at the outpatient service of the Department of Neonatology. According to thyroid function test results, they were divided into an abnormal thyroid function group (observation group; n=31) and a normal thyroid function group (control group; n=51). The infants in the observation group were given oral administration of levothyroxine sodium tablets, while those in the control group were not given any treatment. The two groups were compared in terms of the physical and intelligence development and thyroid function of preterm infants with various gestational ages (28-<32 weeks, 32-<34 weeks, and 34-<37 weeks) after regular follow-up to the corrected age of 12 months.

RESULTS

There were no significant differences in physical development indices (body length, body weight, and head circumference) between the observation and control groups at various gestational ages after follow-up to the corrected age of 12 months (P>0.05). There were no significant differences between the two groups in the scores of each functional area of the Gesell Developmental Scale among the preterm infants with a gestational age of 28-<32 weeks and 32-<34 weeks after follow-up to the corrected age of 12 months (P>0.05). For the preterm infants with a gestational age of 34-<37 weeks, compared with the control group, the observation group had a significantly lower score of gross motor ability at the age of 3 and 12 months, significantly lower scores of fine motor ability, language ability, and adaptation ability at the age of 12 months (P<0.05), and a significantly lower score of personal-social ability at the age of 3 months (P<0.05). However, the score of personal-social ability in the observation group was not significantly different from the control group at the age of 12 months (P>0.05). After 2-4 weeks of treatment with levothyroxine sodium tablets, the thyroid function of the 31 preterm infants with thyroid dysfunction returned to normal. Among the 31 infants, 21 (68%) achieved complete drug withdrawal, with normal results of neonatal screening (100%); 10 infants (32%) failed to achieve drug withdrawal, and only 2 (20%) out of the 10 infants had normal neonatal screening results (P<0.05).

CONCLUSIONS

Early diagnosis and reasonable treatment can reduce the impact on growth and development in preterm infants with thyroid dysfunction. Most preterm infants tend to have transient thyroid dysfunction, while those with positive results of neonatal screening are more likely to develop permanent thyroid dysfunction.

Long-Term Course of Hypothyroidism Detected through Neonatal TSH Screening in a Population-Based Cohort of Very Preterm Infants Born at Less than 32 Weeks of Gestation

After several decades of successful newborn screening (NBS) for congenital hypothyroidism, the optimal hypothyroidism NBS algorithm for very preterm infants is still controversial. Due to concerns about an elevated risk of a false-negative initial thyroid-stimulation hormone (TSH) screening, repeat NBS has been implemented for this group. While transient hypothyroidism is known to be more frequent among very preterm infants, the prevalence of permanent hypothyroidism is generally assumed to be the same as in more mature newborns. This study analyses screening and long-term follow-up data from the population-based cohort of 51 infants born from 1999-2017 at less than 32 weeks of gestation and diagnosed with hypothyroidism after NBS in the German Federal State of Bavaria (total number of infants screened 2,107,864). Severe permanent hypothyroidism was always detected at initial TSH screening unless there was a known confounding factor. Cases detected by repeat screening after a negative initial screen most frequently proved to be transient, less frequently mild permanent, or a definitive diagnosis was not possible because of inadequate re-evaluation of the thyroid axis. The prevalence of both permanent and transient hypothyroidism was elevated compared to a cohort of children from the same region born at a higher gestational age. The results seem to support the need for the repeated NBS of very preterm infants. However, as the recommendation to treat mild hypothyroidism is not based on high quality evidence, important issues for future research include treatment outcome studies or even a general review of whether this diagnosis meets the screening criteria. Meanwhile, involving a paediatric endocrinologist in treatment decisions is crucial for optimising the benefit of hypothyroidism screening for this particularly vulnerable group.

Evolution of congenital hypothyroidism in a cohort of preterm born children

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.

Frequency of thyroid dysfunction in pediatric patients with congenital heart disease exposed to iodinated contrast media - a long-term observational study

Background The thyroid gland of patients with congenital heart disease may be exposed to large doses of iodine from various sources. We assessed the thyroid response after iodine exposure during conventional angiography in cardiac catheterization and angiographic computer tomography in childhood. Methods Retrospective mid- to long-term follow-up of 104 individuals (24% neonates, 51% infants, 25% children) with a median age and body weight of 104 days [0-8 years] and 5.3 kg [1.6-20]. Serum levels of thyroid-stimulating hormone, free triiodthyronine and free thyroxine were evaluated at baseline and after excess iodine. We also assessed risk factors that may affect thyroid dysfunction. Results Baseline thyroidal levels were within normal range in all patients. The mean cumulative iodinate contrast load was 6.6 ± 1.6 mL/kg. In fact, 75% had experienced more than one event involving iodine exposure, whose median frequency was three times per patient [1-12]. During the median three years follow-up period [0.5-10], the incidence of thyroid dysfunction was 15.4% (n=16). Those patients developed acquired hypothyroidism (transient n=14, long-lasting n=2 [both died]) with 10 of them requiring temporary replacement therapy for transient thyroid dysfunction, while four patients recovered spontaneously. 88 individuals (84.6%) remained euthyroid. Repeated cardiac interventions, use of drugs that interfere with the thyroid and treatment in the intensive care unit at the index date were strong predictors for acquired thyroid dysfunction. Conclusions The incidence of acquired hypothyroidism after iodine excess was 15.4%. However, most patients developed only transient hypothyroidism. Systemic iodine exposure seems to be clinically and metabolically well tolerated during long-term follow-up.