Thyroid Function and Thyroid Hormone Requirements of Very Preterm Infants

Preterm birth is frequently associated with altered thyroid hormone levels in the newborn period. Recent data suggest a role of prematurity independent of birth size also in childhood thyroid dysfunction. Whether the high-risk population of former very preterm infants (VPI) is particularly susceptible to thyroid hormone alterations is currently unknown. The aim of the present study was to assess whether former VPI display changes in thyroid hormone status in comparison to term-born controls at a preschool age. Free triiodothyronine (fT3), free thyroxine (fT4), and thyroid stimulating hormone (TSH) concentrations were determined in former VPI and same-aged children born at term at five to seven years of age. 31 former term infants and 82 former VPI were included in the study. In comparison to children born at term, former VPI had lower fT4 (16.1±1.8 versus 17.0±2.1 pmol/l), higher fT3 (6.8±0.7 versus 6.5 pmol/l), and higher TSH levels (3.0±1.4 versus 2.3±1.0 μU/l), independent of major neonatal morbidities. As subclinical changes in thyroid hormone status are potentially associated with adverse health profiles, close follow-up of these children is warranted.

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Dynamic Change of Thyroid Hormones With Postmenstrual Age in Very Preterm Infants Born With Gestational Age <32 Weeks: A Multicenter Prospective Cohort Study

Frontiers in Endocrinology ◽

10.3389/fendo.2020.585956 ◽

2021 ◽

Vol 11 ◽

Author(s):

Ranran Shi ◽

Ming Zhang ◽

Yao Chen ◽

Meiying Han ◽

Ping Xu ◽

...

Keyword(s):

Cohort Study ◽

Preterm Infants ◽

Thyroid Function ◽

Gestational Age ◽

Prospective Cohort ◽

Term Infants ◽

Very Preterm Infants ◽

Very Preterm ◽

Postmenstrual Age ◽

The Relationship

BackgroundAt present, the relationship between thyrotropin (TSH) and free thyroxine (FT4) in relation to postmenstrual age (PMA) in preterm infants is still unclear, and there is no reliable standard thyroid hormone reference ranges, resulting in different diagnostic criteria for congenital hypothyroidism been used by different newborn screening programs and different countries.ObjectivesTo investigate the relationship between TSH/FT4 and PMA in very preterm infants (VPIs) born with gestational age (GA) <32 weeks and to derive thyroid function reference charts based on PMA.MethodsA prospective cohort study was performed on VPIs born with GA<32 weeks and born in or transferred to the 27 neonatal intensive care units from January 1, 2019 to December 31, 2019. Serial TSH and FT4 values were measured at the end of each week during the first month after birth and also at PMA36 weeks, PMA40 weeks and at discharge, respectively. The 2.5th, 5th, 50th, 95th, and 97.5th percentiles of TSH and FT4 of different PMA groups were calculated to draw the percentile charts based on PMA.Results1,093 preterm infants were included in this study. The percentile charts of TSH and FT4 levels based on PMA were drawn respectively, and the result indicated that the percentile charts of TSH values were gradually increased initially and then decreased with increasing PMA. The 97.5th percentile chart reached the peak at PMA30 weeks (17.38μIU/ml), and then decreased gradually, reaching the same level as full-term infants (9.07μIU/ml) at PMA38–40 weeks. The 2.5th percentile chart of FT4 was at its lowest point at PMA26–27 weeks (5.23pmol/L), then increased slowly with PMA and reached the same level as full-term infants at PMA38–40 weeks (10.87pmol/L). At PMA36 weeks, the reference intervals of the 2.5th to 97.5th percentiles of TSH and FT4 were 1.18–12.3μIU/ml and 8.59–25.98pmol/L, respectively.ConclusionThe percentile charts of TSH and FT4 in VPIs showed characteristic change with PMA. The results prompt that age-related cutoffs, instead of a single reference range, might be more useful to explain the thyroid function of VPIs. And repeated screening is necessary for preterm infants.

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