Thyroid Function in Very Preterm Newborns: Possible Implications

Wassenaer, Aleid G. van; Kok, Joke H.; Briët, Judy M.; Pijning, Arjan.; Vijlder, J J de

doi:10.1089/thy.1999.9.85

Cited by 42 publications

(28 citation statements)

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“…This transient hypothyroxinemia may influence certain brain structures, and the degree of postnatal thyroid hormone surge is influenced by gestational age. 17,18 Although the precise relationship with the STN and globus pallidus remains to be established, these maternal and fetal/infant hormones might play some role in the development of these structures and result in the signal intensity changes observed on MR imaging in the present study. Normal signal intensity changes also are seen in other parts of the brain such as anterior pituitary lobe that also depends on postnatal age.…”

Section: Discussionmentioning

confidence: 75%

Transient Hyperintensity in the Subthalamic Nucleus and Globus Pallidus of Newborns on T1-Weighted Images

Taoka¹,

Aida²,

Ochi³

et al. 2011

AJNR Am J Neuroradiol

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BACKGROUND AND PURPOSE:In the brains of newborns, changes in signal intensity in most structures can be explained by the development of myelination. However, there are some structures for which signal intensity changes cannot be accounted for by myelination alone. We examined the STN and globus pallidus signal intensities and tried to determine whether a relationship exists between the signal intensity and the postnatal age or the gestational age at the examination.

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Section: Discussionmentioning

confidence: 75%

Transient Hyperintensity in the Subthalamic Nucleus and Globus Pallidus of Newborns on T1-Weighted Images

Taoka¹,

Aida²,

Ochi³

et al. 2011

AJNR Am J Neuroradiol

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“…Preterm serum T 4 and FT 4 concentrations are lower than those of term infants, but the TSH concentrations are comparable to term infants. 49,50 Serum TBG concentrations are only slightly low in preterm infants and do not account for the degree of hypothyroxinemia. Consequently, the FT 4 is rarely as low as the total T 4 .…”

Section: Low T 4 and Normal Tsh Valuesmentioning

confidence: 99%

Update of Newborn Screening and Therapy for Congenital Hypothyroidism

Rose¹,

Brown²

2006

Pediatrics

582

301

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Unrecognized congenital hypothyroidism leads to mental retardation. Newborn screening and thyroid therapy started within 2 weeks of age can normalize cognitive development. The primary thyroid-stimulating hormone screening has become standard in many parts of the world. However, newborn thyroid screening is not yet universal in some countries. Initial dosage of 10 to 15 g/kg levothyroxine is recommended. The goals of thyroid hormone therapy should be to maintain frequent evaluations of total thyroxine or free thyroxine in the upper half of the reference range during the first 3 years of life and to normalize the serum thyroid-stimulating hormone concentration to ensure optimal thyroid hormone dosage and compliance.Improvements in screening and therapy have led to improved developmental outcomes in adults with congenital hypothyroidism who are now in their 20s and 30s. Thyroid hormone regimens used today are more aggressive in targeting early correction of thyroid-stimulating hormone than were those used 20 or even 10 years ago. Thus, newborn infants with congenital hypothyroidism today may have an even better intellectual and neurologic prognosis. Efforts are ongoing to establish the optimal therapy that leads to maximum potential for normal development for infants with congenital hypothyroidism.Remaining controversy centers on infants whose abnormality in neonatal thyroid function is transient or mild and on optimal care of very low birth weight or preterm infants. Of note, thyroid-stimulating hormone is not elevated in central hypothyroidism. An algorithm is proposed for diagnosis and management.Physicians must not relinquish their clinical judgment and experience in the face of normal newborn thyroid test results. Hypothyroidism can be acquired after the newborn screening. When clinical symptoms and signs suggest hypothyroidism, regardless of newborn screening results, serum free thyroxine and thyroidstimulating hormone determinations should be performed. INTRODUCTIONCongenital hypothyroidism (CH) is one of the most common preventable causes of mental retardation. In most cases, the disorder is permanent and results from an All clinical reports from the American Academy of Pediatrics automatically expire 5 years after publication unless reaffirmed, revised, or retired at or before that time.The guidance in this report does not indicate an exclusive course of treatment or serve as a standard of medical care. Variations, taking into account individual circumstances, may be appropriate.Key Words congenital hypothyroidism, thyroid hormone, thyroid-stimulating hormone, newborn screening Abbreviations CH-congenital hypothyroidism TH-thyroid hormone T 4 -thyroxine T 3 -triiodothyronine TSH-R-thyrotropin receptor TRBAb-thyrotropin receptor-blocking antibody FT 4 -free thyroxine TSH-thyroid-stimulating hormone TBG-thyroid-binding globulin LBW-low birth weight VLBW-very low birth weight L-T 4 -levothyroxine TRH-thyrotropin-releasing hormone PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).

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“…In an earlier study, we found higher heart rates in children who received only T 4 (23). For studying the effects of T 3 plus T 4 administration on the cardiovascular system, intra-arterial blood pressure, heart rates, and cumulative doses of inotropic agents were measured in all infants included in the current study.…”

mentioning

confidence: 92%

A Randomized, Masked Study of Triiodothyronine Plus Thyroxine Administration in Preterm Infants Less Than 28 Weeks of Gestational Age: Hormonal and Clinical Effects

et al. 2004

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A randomized, placebo-controlled, masked study was conducted of the responses of thyroid parameters, cortisol, and the cardiovascular system to a single dose of triiodothyronine (T 3 ) 24 h after birth, followed by a daily dose of thyroxine (T 4 ) during 6 wk to infants Ͻ28 wk gestational age. Thirty-one infants were assigned to three groups: 1) group A: T 3 24 h after birth plus daily T 4 during 6 wk; 2) group B: placebo T 3 and T 4 during 6 wk; and 3) group C: placebo T 3 and placebo T 4 . T 4 , free T 4 , T 3 , free T 3 , reverse T 3 , thyroid-stimulating hormone, and cortisol were measured in cord blood and on days 1, 3, 7, 14, 21, 42, and 56. Data on pulse rate, blood pressure, and cumulative dose of inotropic agents were collected. T 3 (0.5 g/kg) resulted in a plasma increase until day 3. Thereafter, plasma T 3 levels were comparable between the groups. T 4 , free T 4 , and reverse T 3 were increased in groups A and B during the period of T 4 administration. Thyroid-stimulating hormone suppression was of shorter duration in group A. T 3 and T 4 administration did not have any effect on cortisol levels. We did not find any effects of T 3 or of T 4 administration on the cardiovascular system. A single injection of T 3 (0.5 g/kg) given 22-26 h after birth only leads to a 2-d increase of T 3 levels and does not have effects on the cardiovascular system. This study does not support the use of T 3 according to our regimen in preterm infants. Thyroid hormones play an important role in normal growth and development of the CNS (1, 2). In term infants, thyroxine (T 4 ) and triiodothyronine (T 3 ) increases shortly after birth. In premature infants, transient hypothyroxinemia after birth is a common finding (3-7). This hypothyroxinemia is characterized by low levels of T 4 and T 3 , which do not cause elevations in thyroid-stimulating hormone (TSH) above 20 mU/L. The degree of hypothyroxinemia is related to gestational age (GA) and the severity of neonatal disease. Low T 3 and T 4 levels in premature infants have been found to be associated with poor neurologic and developmental outcome (8 -11).Transient hypothyroxinemia is a multicausal phenomenon in which immaturity of thyroid hormone metabolism with high activity of deiodinase type 3 together with factors such as immaturity of the hypothalamo-pituitary-thyroid axis and the sudden interruption of the maternal contribution to fetal thyroid hormone pools are involved. Thyroid hormone supplementation in preterm infants has been the subject of several clinical studies with clinical and neurodevelopmental parameters as primary outcome (12)(13)(14). To date, no clear effect of supplemental T 4 treatment on neurodevelopmental outcome has been demonstrated. In an earlier study, however, we observed that a subgroup of T 4 -treated infants of Ͻ29 wk GA tended to have a better developmental outcome than infants of similar GA in the placebo group (13,15).T 4 administration to preterm infants of Ͻ30 wk GA did not result in increased plasma T 3 levels; in fact, it resulted in de...

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Thyroid Function in Very Preterm Newborns: Possible Implications

Cited by 42 publications

References 30 publications

Transient Hyperintensity in the Subthalamic Nucleus and Globus Pallidus of Newborns on T1-Weighted Images

Transient Hyperintensity in the Subthalamic Nucleus and Globus Pallidus of Newborns on T1-Weighted Images

Update of Newborn Screening and Therapy for Congenital Hypothyroidism

A Randomized, Masked Study of Triiodothyronine Plus Thyroxine Administration in Preterm Infants Less Than 28 Weeks of Gestational Age: Hormonal and Clinical Effects

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