Neonatal Med.  2019 Nov;26(4):204-212. 10.5385/nm.2019.26.4.204.

Risk Factors for Delayed Hyperthyrotropinemia in Late Preterm Infants

• Jeong MH
• Lee N
• Bae MH
• Han YM
• Park KH
• Byun SY

• KMID: 2466640
• DOI: http://doi.org/10.5385/nm.2019.26.4.204

Abstract

PURPOSE
This study aimed to investigate the prevalence of delayed thyroid dysfunction based on iodine disinfectant use and to analyze associated risk factors.
METHODS
A retrospective study was conducted on late preterm infants admitted to the neonatal intensive care unit between January 2010 and June 2018, who underwent neonatal thyroid screening (NTS) and ≥2 thyroid function tests (TFTs). NTS was performed 3 days after birth, with at least two TFTs 1 week and 2 to 4 weeks after birth. To distinguish between normal and dysfunctional thyroid levels, we reviewed TFT results at 2 to 4 weeks and examined possible risk factors for the development of thyroid dysfunction.
RESULTS
Of 295 late preterm infants, 262 were enrolled with a mean gestational age and birth weight of 34.8±0.7 weeks and 2,170±454 g, respectively. A total of 7.6% developed hyperthyrotropinemia at the age of 24.3±14.6 days (range, 12 to 69). The incidence of hyperthyrotropinemia during iodine use was approximately 12.6%, while that during discontinuation was 2.4% (P=0.002). Multivariate analysis revealed that small for gestational age (SGA), iodine disinfectant use, and abnormal NTS results were significant risk factors for delayed hyperthyrotropinemia (adjusted odds ratio [AOR]: 4.27, P=0.008; AOR: 8.24, P=0.003; and AOR: 7.80, P=0.002, respectively).
CONCLUSION
Delayed hyperthyrotropinemia was prevalent in late preterm infants exposed to topical iodine and those identified as being SGA. Secondary TFTs should be considered 2 to 4 weeks after birth for this population at risk.

Keyword

Congenital hypothyroidism; Iodine; Infant, premature; Small for gestational age; Thyrotropin

MeSH Terms

Birth Weight
Congenital Hypothyroidism
Gestational Age
Humans
Incidence
Infant, Newborn
Infant, Premature*
Intensive Care, Neonatal
Iodine
Mass Screening
Multivariate Analysis
Odds Ratio
Parturition
Population Characteristics
Prevalence
Retrospective Studies
Risk Factors*
Thyroid Function Tests
Thyroid Gland
Thyrotropin
Iodine
Thyrotropin

Figure

• 

  Figure 1. Flowchart of study population selection. Abbreviations: VACTERL association, associated vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities; NTS, neonatal thyroid screening; FT4, free thyroxine; TSH, thyroid-stimulating hormone (thyrotropin).

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