Biomedical subjects

Aleid G van Wassenaer

Publications and source records attributed to Aleid G van Wassenaer.

8 recordsLinked to original sources

PubMed2006

Neonatal thyroxine supplementation for transient hypothyroxinemia of prematurity : beneficial or detrimental?

Extremely low birth-weight newborns (<1000g) experience low levels of thyroid hormone that vary inversely with the severity of neonatal illness and the extent of developmental immaturity with levels reaching a nadir at approximate, equals7 days after birth; this phenomenon can persist for several weeks. In the absence of transplacental passage, 30-50% of these neonates cannot generate sufficient quantities of thyroid hormone to meet postnatal demands, placing them at an increased risk for developmental delay and cerebral palsy. Population surveys and interventional trials suggest that a therapeutic opening exists during a 'window of opportunity' corresponding to this period of diminished capacity. Variables to consider before intervention focus on the consideration that supplementation of both the substrate thyroxine and the active hormone triiodothyronine may be necessary in quantities that do not suppress thyroid-stimulating hormone release, yet overcome the persistence of increased conversion to 3,3'5'-triodo-L-thyronine, terminal deiodination, and activity of the sulfation inactivation pathways, as well as the diminished capacity of the newborn to accommodate postnatal physiologic changes. Single daily replacement doses may suppress levels of converting enzymes in the brain, suggesting that physiologic 'mimicry' provided by a constant infusion may be the preferred dosing option. Properly powered clinical trials targeting long-term developmental outcomes are needed to discern whether these interventions will do more than simply elevate blood levels of thyroid hormones to the target values of either the fetus or developing neonate. Identifying the appropriate indications for supplementation may alleviate individual pain and distress due to disability for several hundred extremely low birth-weight neonates each year in the US alone, and save society a pro-rated lifetime cost of nearly $US1 million per child.

Humans↗

PubMed2005

Ten-year follow-up of children born at <30 weeks' gestational age supplemented with thyroxine in the neonatal period in a randomized, controlled trial.

BACKGROUND: Thyroid hormones are essential for brain development. We conducted a randomized, controlled trial with thyroxine (T4) supplementation in infants <30 weeks' gestation and with the last neurodevelopmental follow-up moment at the age of 5.5 years. T4 supplementation was associated with improved outcome of infants <28 weeks' gestation and worse outcome of infants of 29 weeks' gestation. We studied gestational age-dependent effects of T4 supplementation at the mean age of 10.5 years in children participating in our randomized, controlled trial. METHODS: Questionnaires regarding school outcome, behavior, quality of life, motor problems, and parental stress were sent to the parents and children and their teachers at the same time point for all surviving children (9-12 years of age). RESULTS: Seventy-two percent of the families responded to our questionnaires. Nonrespondents had more sociodemographic risk factors and worse development until 5.5 years. At the mean age of 10.5 years, T4 supplementation was associated with better school outcome in those who were <27 weeks' gestation and better motor outcome in those who were <28 weeks' gestation, whereas the reverse was true for those who were born at 29 weeks' gestation. No other gestational age-dependent outcomes were found. CONCLUSIONS: Gestation-dependent effects of T4 supplementation remain stable over time. These effects do not prove beneficial effects of T4 in infants <28 weeks but should be the background for a new randomized, controlled trial with thyroid hormone in this age group.

Brain↗

PubMed2005

Very preterm birth is associated with disabilities in multiple developmental domains.

OBJECTIVE: Follow-up studies in very preterm children usually present outcome for separate developmental domains. Presence of disabilities in more than one developmental domain will show a more serious outcome picture for extreme preterm infants and may be related to a different degree of perinatal problems. METHODS: At 5.5 years corrected age, outcome in the neurological, motor, cognitive, and behavioral domain was studied in 157 children born < 30 weeks gestation. The children were divided into a normal, a single, or a multiple disability group. Group differences in background, clinical characteristics, and neurodevelopmental outcome at 2 years were evaluated. RESULTS: Thirty-nine percent had a normal developmental outcome, 17% had a single disability, and 44% had multiple disabilities. Multiple disabilities were associated with lower birth weight, BPD, and difficulties according to neurodevelopmental assessments at 2 years. CONCLUSION: Assessments of different developmental domains show that most very preterm children had multiple disabilities.

Achievement↗

PubMed2005

Transient hypothyroxinemia in severe hypertensive disorders of pregnancy.

OBJECTIVE: Assess whether and to what extent thyroid function is affected in pregnant women with early and severe hypertensive disorders and in their newborns. METHODS: Patients were 80 women with preeclampsia, hemolysis, elevated liver enzymes, and low platelet count syndrome or gestational hypertension combined with fetal growth restriction in the 24th to 34th week of singleton pregnancies. Maternal thyroid hormone levels and thyroid peroxidase antibodies were determined at admission and 3 months postpartum. Neonatal levels were determined from cord blood at delivery. Maternal hypothyroxinemia was defined as free T(4) (fT(4)) value below 9 pM. RESULTS: At admission 26 (33%) women in the study group had fT(4) levels below 9 pM, with spontaneous normalization during pregnancy. There were no statistically significant differences between thyroid hormone values in women in the study group and 10 normotensive pregnant women in their third trimester. Three months postpartum, 97.5% of patients had normal thyroid hormone levels. Thyroid peroxidase antibodies were elevated in 10% of women postpartum. Their infants, born at a median gestational age of 30 6/7 weeks, had lower cord blood fT(4) and thyroid-stimulating hormone values compared with preterm infants of the comparison group, appropriate for gestational age. Cord blood fT(4) had no correlation with gestational age or maternal fT(4), but there was a significant correlation of cord blood fT(4) with umbilical artery pH. CONCLUSION: Women with severe hypertensive disorders of pregnancy may have transiently lower fT(4) levels, without evidence of a thyroid disorder. Their neonates have lower fT(4) levels at birth unrelated to maternal fT(4), but related to prenatal acidosis. LEVEL OF EVIDENCE: II-2.

Adult↗

PubMed2004

Hypothyroxinaemia and thyroid function after preterm birth.

The concentration of thyroid hormone in preterm infants is lower than that in term infants. This phenomenon is referred to as transient hypothyroxinaemia of prematurity. Low thyroid hormone levels after very preterm birth are associated with worse developmental outcome in childhood, but only one randomized controlled trial has been carried out in the surfactant era to find out whether thyroid hormone supplementation is beneficial for developmental outcome. More studies are required to find out whether thyroid hormone supplementation is beneficial, and if so, for which preterm group.

Drug Administration Schedule↗

PubMed2003

A randomized, masked study of triiodothyronine plus thyroxine administration in preterm infants less than 28 weeks of gestational age: hormonal and clinical effects.

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 <28 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 microg/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 microg/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.

Drug Therapy, Combination↗

PubMed2002

The quantity of thyroid hormone in human milk is too low to influence plasma thyroid hormone levels in the very preterm infant.

BACKGROUND: Thyroid hormone is crucial for brain development during foetal and neonatal life. In very preterm infants, transient low levels of plasma T4 and T3 are commonly found, a phenomenon referred to as transient hypothyroxinaemia of prematurity. We investigated whether breast milk is a substantial resource of thyroid hormone for very preterm neonates and can alleviate transient hypothyroxinaemia. Both the influence of breast feeding on plasma thyroid hormone levels and the thyroid hormone concentration in preterm human milk were studied. METHODS: Two groups were formed from the placebo group of a randomized thyroxine supplementation trial in infants born at < 30 weeks' gestational age on the basis of the mean breast milk intake during the third, fourth and fifth weeks of life. One group received more than 50% breast milk (mean breast milk intake 84%, n = 32) and the other group less than 25% breast milk (mean breast milk intake 3.3%, n = 25). Plasma thyroid hormone concentrations were compared between the two groups. Breast milk was collected from mothers of infants participating in the same trial and the thyroxine concentration in breast milk was measured with RIA after extraction. RESULTS: No significant differences were found between both groups in plasma concentrations of T4, free T4, T3, TSH, rT3 and thyroxine-binding globulin (TBG), which were measured once a week. Thyroxine concentration in breast milk ranged between 0.17 microg/l and 1.83 microg/l (mean 0.83, SD 0.3 microg/l) resulting in a maximum T4 supply of 0.3 microg/kg via ingested breast milk. In formula milk, the T4 concentration was equally low. Protease treatment did not influence the measured T4 concentrations. CONCLUSIONS: No differences in plasma thyroid hormone between breast milk-fed and formula-fed infants were found. The amount of T4 present in human milk and formula milk is too low to alter the hypothyroxinaemic state of preterm infants.

Adult↗

PubMed2002

Free thyroxine levels during the first weeks of life and neurodevelopmental outcome until the age of 5 years in very preterm infants.

BACKGROUND: We have conducted a randomized trial with thyroxine (T4) in 200 infants <30 weeks' gestation. T4 treatment was associated with better 5-year outcome in infants <29 weeks' gestation, but with worse outcome in infants of 29 weeks. These effects could be related to low, respectively high free thyroxine (FT4) levels METHODS: For each infant, the average FT4 of 5 scheduled measurements was calculated between day 3 and day 28. Infants of the placebo and the T4 group separately were divided in 2 groups. The placebo group consisted of a group of infants with average FT4 in the lowest quartile and a group in the upper 75%. The T4 group consisted of a group of infants with average FT4 in the upper quartile and a group in the lower 75%. Developmental outcome (mental/cognitive, motor, and neurologic) at 2 and 5.7 years was compared between high and low FT4 groups, and then compared separately for the T4 and placebo group. RESULTS: In the placebo group, low FT4 was associated with worse outcome on all domains at both time points. After correction for confounding variables, mental and neurologic outcome remained significantly different at 2 years, and motor outcome at 5 years. In the T4 group, high FT4 was not associated with worse outcome, neither at 2 nor at 5 years. CONCLUSIONS: In untreated infants, low FT4 values during the first 4 weeks after birth in infants born at <30 weeks' gestation are associated with worse neurodevelopmental outcome at 2 and 5 years. In T4-treated infants, high FT4 is not associated with worse outcome. Other factors than high FT4 concentrations must play a role in the worse outcome of the T4-treated group of 29 weeks' gestational age.

Child Development↗