Low thyroxinaemia occurs in the majority of very preterm newborns

Rooman, Raoul; Caju, du Marc; Beeck, op de Lieve; Docx, M.; Reempts, van Patrick; Acker, van Karel J. M.

doi:10.1007/bf01953940

Cited by 99 publications

(97 citation statements)

References 25 publications

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“…Reference ranges for thyroid function tests in premature infants exist, but there are limitations. Some authors provide data for groups of gestational ages, 2,17,18 some restrict data to 'healthy' premature infants, 17,18 while others use unselected infants; 13 and some data are based on measurements taken at any point within the first week of life (although excluding the first 24 h) 17 (Table 1). So when should thyroid hormones, TSH and TBG be measured?…”

Section: Measurement Of Thyroid Hormones For Classification Of Transimentioning

confidence: 99%

The measurement, definition, aetiology and clinical consequences of neonatal transient hypothyroxinaemia

Williams

Hume

2010

Ann Clin Biochem

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This review focuses on neonatal transient hypothyroxinaemia, a condition characterized by temporary postnatal reductions in concentrations of Total T4 or Free T4, with normal or low concentrations of thyroid stimulating hormone (TSH). There is neither an agreed quantitative definition, nor an agreed mode of measurement for the condition. Transient hypothyroxinaemia is not routinely monitored yet it is thought to affect about 50% of preterm infants; it was thought to be without long-term sequelae but observational studies indicate that neurodevelopment may be compromised. The aetiology of transient hypothyroxinaemia is complex. There are significant contributions from the withdrawal of maternal -placental thyroxine transfer, hypothalamic-pituitary -thyroid immaturity, developmental constraints on the synthesis and peripheral metabolism of iodothyronines and iodine deficiency. It is not possible to distinguish clinically, or from laboratory measurements, whether transient hypothyroxinaemia is an independent condition or simply a consequence of non-thyroidal illness and/or drug usage. An answer to this question is important because studies of thyroid hormone replacement have been instigated, with mixed results. Until the aetiology of transient hypothyroxinaemia is better understood it would seem prudent not to routinely supplement preterm infants with thyroid hormones. Iodine deficiency, non-thyroidal illness and drug usage are the most modifiable risk factors for transient hypothyroxinaemia and are the clear choices for attempts at reducing its incidence. We suggest that transient hypothyroxinaemia in preterm infants is defined as a normal or low TSH concentration in conjunction with a concentration of Total T4, that is 10th percentile of cord Total T4 of the equivalent gestational age had the infant remained in utero.Ann Clin Biochem 2011; 48: 7-22.

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Section: Measurement Of Thyroid Hormones For Classification Of Transimentioning

confidence: 99%

The measurement, definition, aetiology and clinical consequences of neonatal transient hypothyroxinaemia

Williams

Hume

2010

Ann Clin Biochem

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“…Therefore, it was proposed to measure free T4 in all preterms with gestational age below 33 weeks during the second week of life. 26 After reviewing our results for CH, improvements in our program can be achieved through the following considerations: First, the frequency of abnormal TSH results can be reduced by almost half, if age-adjusted reference ranges are used, especially in the first 3 days of life. 27 Second, infants with non-elevated TSH and low thyroxine that might be missed by TSH testing alone can be prevented by clinical suspicion and re-screening using both TSH and T4.…”

Section: Hypothyroidismmentioning

confidence: 99%

A Neonatal Screening in Lebanon: Results of Five Years’ Experience

et al. 2003

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Background: Neonatal screening programs for common disorders like phenylketonuria, congenital hypothyroidism, and glucose-6-phosphate dehydrogenase (G6PD) deficiency are not fully established at the national level in Lebanon. Screening for the above disorders was carried out for newborns delivered at the American University of Beirut Medical Center over a period of five years. Subjects and Methods: Blood specimens collected 2-3 days after birth were applied to neonatal screening blood collection cards. A total of 9117 newborns were screened using phenylalanine, thyroid-stimulating hormone, and G6PD activity measurements on blood spots. Results: One case of phenylketonuria and another of hyperphenylalaninemia were detected. We also detected 5 cases of permanent type congenital hypothyroidism, giving an incidence of 5:9117 (1:1823). The age range at initiation of hormonal replacement therapy was 9-46 days. The overall incidence of G6PD was 106:9117 (1:86 or 1.16%), of which 84 had complete deficiency (1:109 or 0.92%), and 22 with intermediate activity. Conclusion:The incidence of these disorders found in this Lebanese sub-population warrants consideration of a comprehensive nationwide neonatal screening program.

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“…These neonates have a problem with autoregulation of thyroidal iodine uptake as well as an immature hypothalamic-pituitarythyroid axis resulting in an inability to compensate for the loss of maternal T4 supply in the short term (Rooman et al 1996, Ares et al 1997, Delbert & Fisher 1997a, Van Wassenaer et al 1997. Comparing free T4 concentrations of premature infants with intrauterine fetuses of similar gestational age revealed a 50% difference initially, a phenomenon not observed in term babies (Ares et al 1997).…”

Section: Intrauterine Growth Restriction and Prematurity In Human Prementioning

confidence: 99%

Thyroid hormone and central nervous system development

Chan¹,

Kilby²

2000

Journal of Endocrinology

187

115

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Low thyroxinaemia occurs in the majority of very preterm newborns

Abstract: Very preterm neonates have FT4 levels on day 14 that are much lower than is generally assumed while TSH remains in the normal range. We therefore propose to measure FT4 in all preterms with a GA below 33 weeks, during the 2nd week of life.

Cited by 99 publications

References 25 publications

The measurement, definition, aetiology and clinical consequences of neonatal transient hypothyroxinaemia

The measurement, definition, aetiology and clinical consequences of neonatal transient hypothyroxinaemia

A Neonatal Screening in Lebanon: Results of Five Years’ Experience

Thyroid hormone and central nervous system development

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