Median nerve conduction velocity and central conduction time measured with somatosensory evoked potentials in thyroxine-treated infants with Down syndrome

Prospective study of thyroid function in the first year of life in infants with Down syndrome

Current American Academy of Pediatrics (AAP) Guidelines recommend monitoring thyroid function in infants with Down syndrome (DS) at birth, 6 and 12 months, and annually thereafter. This study aimed to determine whether these guidelines are optimal for early diagnosis and treatment of (subclinical) hypothyroidism. Enrolled infants with DS less than age 7 months, born at ≥ 30 weeks gestation to monitor thyroid function test (TFT). A filter paper (FP) blood sample was analyzed for TSH and total T4 at ages 2 and 4 weeks and monthly thereafter until 12 months. Subjects with abnormal FP sample and confirmatory serum TFT for hypothyroidism promptly started treatment. Subjects with thyroid dysfunction identified had thyroid antibodies measured at diagnosis and 12 months. Descriptive statistics determined average time to diagnosis of abnormal TFT. Sixteen (30%) of 54 subjects were diagnosed with a thyroid disorder, the majority with subclinical hypothyroidism (SH) and 1 with hyperthyroidism. Diagnosis occurred in 6 (11%), 9 (17%), and 12 (22.2%) infants in the first 30, 60, and 90 days of life (DOL), respectively. Eight infants had an abnormal NBS and half were diagnosed with a thyroid disorder by DOL 8 and the remainder prior to 4 months. Among subjects with a normal NBS, four were diagnosed at a mean of 104 days and three at a mean of 101 days prior to the 6-month and 12-month routine screens, respectively.  Conclusion: Based on current AAP guidelines, thyroid disorder diagnosis would have been delayed in nearly 20% of the subjects. An additional TFT screen at 1 and 3 months can lead to earlier diagnosis and treatment. What is Known: • Current American Academy of Pediatrics (AAP) Guidelines recommend thyroid function tests (TFT) in infants with Down syndrome (DS) at birth and 6 and 12 months. • Peer- reviewed retrospective studies report an increased incidence of hypothyroidism in infants with DS undetected by the newborn screen (NBS) and prior to 6 months. What is New: • This prospective study monitored TFT in infants with DS at age 2 weeks and monthly throughout the first year of life. • The findings in this study support additional TFT screens at 1 and 3 months in infants with DS.

Increased neonatal thyrotropin in Down syndrome

AIM

Down syndrome (DS) is frequently associated with thyroid dysfunction. The aim of this study was to investigate the blood concentration of thyrotropin (TSH) observed at neonatal screening of infants with DS and its possible association with development of hypothyroidism during childhood.

METHODS

TSH levels from neonatal screening of 73 children (34 F) with DS born in 1986-1996 were studied retrospectively and compared with those of controls. The DS children were followed up regarding thyroid function to the age of 10 years in this descriptive study.

RESULTS

The DS infants had a higher mean TSH level and a higher TSH standard deviation score (SDS) than controls (7.0 +/- 7.45 mU/L vs. 3.9 +/- 2.43 mU/L and 1.1 +/- 2.67 vs. 0, respectively). The differences were mainly attributable to higher values in the male DS children. The TSH level at screening did not predict thyroid dysfunction during childhood.

CONCLUSION

Infants with DS, especially boys, showed elevated levels of TSH at neonatal screening, indicating the occurrence of mild hypothyroidism already in early life. The TSH levels could not predict development of manifest thyroid disease later in childhood.