Thyroid Hormone Function in Small for Gestational Age Term Newborns.

OBJECTIVE: To test the hypothesis that term-born small for gestational age (SGA) neonates have elevated thyroid-stimulating hormone (TSH) concentrations and an increased incidence of congenital hypothyroidism compared with non-SGA term neonates. STUDY DESIGN: This retrospective cohort study included all term neonates screened in Wisconsin in 2015 and 2016. The cohort was divided based on SGA status, defined as birth weight <10th percentile as calculated from the World Health Organization's sex-specific growth charts for age 0-2 years. TSH concentration on first newborn screening performed between birth and 96 hours of life and incidence of congenital hypothyroidism were compared between the SGA and non-SGA groups. RESULTS: A total of 115 466 term neonates, including 11 498 (9.96%) SGA neonates, were included in the study. TSH concentration and incidence of congenital hypothyroidism was significantly higher in the SGA group, but only TSH concentration remained significant when adjusted for potential confounding variables. CONCLUSIONS: Our data do not support a higher incidence of congenital hypothyroidism in term SGA neonates after adjusting for potential confounders. However, TSH concentrations were higher in term SGA neonates compared with term non-SGA neonates. The effects of mild thyroid hormone dysfunction on neurodevelopmental outcomes and development of chronic medical conditions merit long-term study.

Treatment Discontinuation within 3 Years of Levothyroxine Initiation among Children Diagnosed with Congenital Hypothyroidism.

OBJECTIVES: To measure the rates of thyroid gland imaging and levothyroxine (L-T4) discontinuation and to assess whether discontinuation was monitored with thyroid-stimulating hormone testing in subjects with congenital hypothyroidism. STUDY DESIGN: This is a retrospective analysis of claims data from the IBM MarketScan Databases for children born between 2010 and 2016 and continuously enrolled in a noncapitated employer-sponsored private health insurance plan or in Medicaid for ≥36 months from the date of the first filled L-T4 prescription. RESULTS: There were 263 privately insured and 241 Medicaid-enrolled children who met the inclusion criteria. More privately insured than Medicaid-enrolled children had imaging between the first filled prescription and 180 days after the last filled prescription (24.3% vs 12.9%; P = .001). By 36 months, 35.7% discontinued L-T4, with no difference by insurance status (P = .48). Among those who discontinued, 29.1% of privately insured children and 47.7% of Medicaid-enrolled children had no claims for thyroid-stimulating hormone testing within the next 180 days (P = .01). CONCLUSIONS: Nearly one-third of children with suspected congenital hypothyroidism discontinued L-T4 by 3 years and fewer Medicaid-enrolled than privately insured children received timely follow-up thyroid-stimulating hormone testing. Future studies are indicated to understand the quality of care and developmental outcomes for children with congenital hypothyroidism and barriers to guideline adherence in evaluating for transient congenital hypothyroidism.

Increased Congenital Hypothyroidism Detection in Preterm Infants with Serial Newborn Screening.

OBJECTIVES: To determine the incidence of congenital hypothyroidism in preterm infants and to identify associated risk factors. STUDY DESIGN: A population-based cohort study was performed in preterm infants born at <32 weeks of gestational age between 2012 and 2016 in Wisconsin. Newborn screening (NBS) results and demographic data were obtained from the Wisconsin State Laboratory of Hygiene. Congenital hypothyroidism was subdivided to early TSH elevation (eTSH) and delayed TSH elevation (dTSH). Multivariate logistic regression analyses were performed to identify demographic factors associated with dTSH. RESULTS: A total of 3137 preterm infants born at 22-31 weeks of gestational age were included in the study. Mean gestational age was 28.4 ± 2.4 weeks and mean birth weight was 1191 ± 399 g. Forty-nine infants were diagnosed with congenital hypothyroidism. The overall incidence of congenital hypothyroidism was 1.56%, including a 0.13% incidence of eTSH and a 1.43% incidence of dTSH. Birth weight <1000 g, multiple gestation, and initial TSH level were identified as independent predictors for dTSH. CONCLUSION: Targeted serial NBS in Wisconsin led to a higher rate of diagnosis of congenital hypothyroidism in preterm infants than has been reported previously. The majority (92%) of congenital hypothyroidism cases were diagnosed with dTSH. Birth weight <1000 g, multiple gestation, and elevated initial TSH level were associated with increased risk for development of dTSH. We recommend obtaining targeted serial NBS in preterm infants (<32 weeks of gestational age) to improve the detection of congenital hypothyroidism.