Levels of Neonatal Thyroid Hormone in Preterm Infants and Neurodevelopmental Outcome at 5½ Years: Millennium Cohort Study

Abstract

Our findings do not support the view that the hypothyroxinemic state, in the context of this analysis, is harmless in preterm infants. Many factors contribute both to the etiology of hypothyroxinemia and neurodevelopment; strategies for correction of hypothyroxinemia should acknowledge its complex etiology and not rely solely on one approach.

Transient hypothyroxinemia of prematurity: Does it have clinical relevance?

“…The brain volume of an infant at 36 weeks GA is only about 60% of that for a term infant [5]. Reduced number of sulci and gyri reflect an anatomic in maturity that is defined by the white matter, myelination and cortical migration of neuronal cells.…”

“…Motor and cognitive deficits are seen in these children despite early thyroxine replacement. Thus, even transiently low thyroxine levels are considered to be a potent risk factor for adverse neurodevelopmental outcome in preterm infants and have been the subject of many elegant long-term studies [1][2][3][4][5]. All cohorts have documented a measure of abnormal mental development in children with THOP.…”

“…In fact, for preterm infants more appropriate levels for comparison of thyroxine values are T 4 /free T 4 levels in cord blood corrected for an equivalent gestational age had the infant remained in utero [5]. Using a cut-off of 10 th centile of cord T 4 corrected for gestational age, Delahunty, et al, [5] found that 20% of all infants born at <34 weeks gestation were hypothyroxinemic, with only 10% being between 31-34 weeks, and rest more premature. Reuss, et al [2] found a 15% incidence of THOP in infants born at <33 weeks gestation using a cut-off of -2.6 SD.…”

Wrodzona niedoczynność tarczycy — polskie rekomendacje dotyczące leczenia, monitorowania terapii i badania przesiewowego w specjalnych kategoriach noworodków z wysokim ryzykiem niedoczynności tarczycy

“…In the study groups with a positive effect of L-thyroxine on the development of preterm babies, a dose of 6-8 μg/kg body weight was used, slightly improving mental development after 5-10 years. However, the greatest problem with decision making is a lack of universal reference values for fT4 and fT3 in preterm newborns [42][43][44][45][46][47][48][49][50][51]. Venous blood TSH values in preterm babies in the first week of life determined with a TSH third-generation test oscillating between 0.7 mIU/l and 27.0 mIU/l [52].…”

“…W dotychczas obserwowanych grupach, w których stwierdzono pozytywny wpływ leczenia L-tyroksyną na rozwój wcześniaków, stosowano dawkę 6-8 μg/kg masy ciała, co powodowało nieco lepszy rozwój umysłowy widoczny po 5-10 latach. Jednak największym problemem przy podejmowaniu decyzji jest brak jednolicie opracowanych wartości referencyjnych fT4 i fT3 u noworodków przedwcześnie urodzonych [42][43][44][45][46][47][48][49][50][51]. Wartości TSH w surowicy krwi żylnej u wcześniaków w pierwszym tygodniu życia oznaczane testem trzeciej generacji oscylują pomiędzy 0,7 mIU/l a 27,0 mIU/l [52].…”