Reference ranges for newer thyroid function tests in premature infants

Adams, Linda M; Emery, Janet R.; Clark, Susan J.; Carlton, Esther; Nelson, Jerald C.

doi:10.1016/s0022-3476(95)70514-7

Cited by 124 publications

(58 citation statements)

References 31 publications

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“…Free T4 and TSH values were compared with normal values for gestational age. 18 For premature infants with a gestational age of 25 to 30 weeks, normal values of free T4 and TSH were 6.4 to 42.5 pM and 0.5 to 29 mU/l, respectively.…”

Section: Laboratory Analysismentioning

confidence: 90%

Parenteral Selenium Supplementation in Extremely Low Birth Weight Infants: Inadequate Dosage But No Correlation With Hypothyroidism

et al. 1999

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Section: Laboratory Analysismentioning

confidence: 90%

Parenteral Selenium Supplementation in Extremely Low Birth Weight Infants: Inadequate Dosage But No Correlation With Hypothyroidism

et al. 1999

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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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“…Transient hypothyroxinemia is common in premature and low birthweight infants (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). Apart from transient low serum concentrations of thyroxine (T 4 ) and free thyroxine (FT 4 ), low concentrations of triiodothyronine (T 3 ) are also found, whereas thyroidstimulating hormone (TSH) concentrations are in the normal range (1).…”

Section: Introductionmentioning

confidence: 99%

“…The reaction of TSH to stimulation by thyrotropin-releasing hormone (TRH) is described as normal (1,9). The degree of hypothyroxinemia is related to gestational age, birthweight and the severity of neonatal disease (1)(2)(3)(4)(5)(6)(7)(8)(9)(10).…”

Section: Introductionmentioning

confidence: 99%

Thyroxine administration to infants of less than 30 weeks gestational age decreases plasma tri-iodothyronine concentrations

Wassenaer¹,

Kok²,

Dekker³

et al. 1998

European Journal of Endocrinology

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Objective: To investigate the effect on thyroid hormone metabolism of the administration of thyroxine to very preterm infants. Design and methods: Two hundred infants of less than 30 weeks gestation were enrolled into a randomized, double-blind, placebo-controlled trial. Thyroxine (T 4 ) (at a fixed daily dose of 8 mg/kg birthweight) or placebo was started 12-24 h after birth and discontinued 6 weeks later. Plasma concentrations of T 4 , tri-idothyronine (T 3 ), reverse T 3 (rT 3 ), TSH, and thyroxine-binding globulin were measured weekly during trial medication and 2 weeks thereafter. Results: The T 4 and the placebo group each comprised 100 infants. Antenatal, perinatal, and postnatal clinical characteristics were comparable in both groups. T 4 and rT 3 were significantly increased in the T 4 group. TSH concentrations were depressed in the T 4 group and T 3 was significantly decreased, probably as a result of TSH depression. The T 4 /T 3 and T 4 /rT 3 ratios differed significantly between the two study groups. Conclusions: Daily T 4 administration during the first 6 weeks after birth to infants of less than 30 weeks gestation prevents hypothyroxinemia, but decreases plasma T 3 concentrations. Our finding possibly implies that very preterm infants should receive supplements of both T 4 and T 3 .

show abstract

Reference ranges for newer thyroid function tests in premature infants

Cited by 124 publications

References 31 publications

Parenteral Selenium Supplementation in Extremely Low Birth Weight Infants: Inadequate Dosage But No Correlation With Hypothyroidism

Parenteral Selenium Supplementation in Extremely Low Birth Weight Infants: Inadequate Dosage But No Correlation With Hypothyroidism

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

Thyroxine administration to infants of less than 30 weeks gestational age decreases plasma tri-iodothyronine concentrations

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