Thyroid function in preterm infants and neurodevelopment at 2 years

Abstract

ObjectivesPostnatal thyroid dysfunction is common in preterm infants but the relationship between mild dysfunction and neurodevelopment is unclear. Our aim is to describe the relationship between thyroid function and neurodevelopment.DesignCohort analysis.Patients1275 infants born under 31 weeks’ gestation; there were no exclusion criteria.SettingThe infants were part of a UK daily iodine supplementation trial.Main outcomesThyroid-stimulating hormone, thyroid-binding globulin and total thyroxine levels were measured in dried blood spots on postnatal days 7, 14, 28 and the equivalent of 34 weeks’ gestation. Neurodevelopment was measured using the Bayley-III Scales of infant development at 2 years of age.ResultsNo infant was identified as hypothyroid through routine screening. The 3% of infants consistently in the top decile of gestationally age-adjusted thyroid-stimulating hormone levels had a reduction in cognitive score of 7 Bayley units when compared with those not in the top decile (95% CI –13 to –1). A reduction in motor composite score of 6 units (95% CI −12 to <−0.1) and fine motor score of 1 unit (95% CI –2 to –0.1) was also identified. The 0.7% of infants consistently in the bottom decile of age-adjusted thyroxine levels had a reduction in motor composite score of 14 units (95% CI –25 to –2) and its two subset scores, fine and gross motor, of 2 units (95% CI respectively −4.5 to <−0.1 and –4.3 to –0.3).ConclusionsPreterm infants with consistent ‘mild’ thyroid dysfunction score less on neurodevelopmental tests at 2 years of age. Many of these infants will not be detected by current clinical protocols or screening programmes.

Postnatal Serum Total Thyroxine of Very Preterm Infants and Long-Term Neurodevelopmental Outcome

“…Importantly, Flores-Robles et al suggested that preterm infants may require lower TT4 cutoff values when undergoing newborn screenings [32]. Preterm infants with consistent thyroid dysfunction should be assessed using multipoint analyses [6,17]. In brief, the authors of this study concluded that the time series of thyroxine concentration screenings, with cutoff values specific to VPIs, is crucial, regardless of whether TT4 or FT4 is chosen as the screening marker.…”

“…For thyroid hormone screenings in very preterm infants, the choice between total thyroxine and free thyroxine (FT4) following national newborn screenings is still under debate. To the best of our knowledge, there is a lack of large-scale research that addresses whether total thyroxine [17,28] or free thyroxine [13,[29][30][31] is optimum for use in postnatal screening, even if free thyroxine is a more active component than total thyroxine. For detecting delayed TSH elevation, in this study, we chose total thyroxine with TSH as the additional marker to be used between the two phases of the national screening policy.…”

“…Recently, Williams et al carried out an extensive study of the role of postnatal total thyroxine (TT4) levels obtained at four time-points without a consideration of morbidities of prematurity. Preterm infants with consistent and mild thyroid dysfunction scored less on neurodevelopmental tests at 24 months of age [17]. Altogether, there are still many unanswered questions about the thyroxine concentrations of VPIs and the long-term neurodevelopmental outcomes.…”

“…However, in those VPIs with TSH < 10.0 µIU/mL, few studies have investigated the level of thyroxin that necessitates thyroxin supplementation. Williams et al voiced concerns regarding the current clinical screening protocols [17]; however, relatively little is known about the optimal timing of extra postnatal screening beyond national newborn screening policies. Furthermore, the effect of any renewal protocol on long-term neurodevelopmental outcomes should be further investigated along with the neonatal morbidities of prematurity [7,9].…”

Impact of iodine supplementation during preconception, pregnancy and lactation on maternal thyroid homeostasis and offspring psychomotor development: protocol of the IodineMinho prospective study

“…This instrument is one of the most reliable and widely used to evaluate children development at 1-42 months. Our group and others have previously used licensed Bayley Scales to address infants' psychomotor performance in the context of maternal hypothyroxinemia [6,20,21]. It includes three subscores: cognitive (information processing, information processing speed, problem-solving, play skills and numbers concepts); language communication (expressive, which is the ability to communicate, and receptive, which includes the abilities to hear, understand and respond) and motor development (fine and gross motor abilities, including movement quality, sensory and perceptual-motor integration and basic locomotion milestones).…”