Results of controlled double-blind study of thyroid replacement in very low-birth-weight premature infants with hypothyroxinemia. Randomised trial of iodine intake and thyroid status in preterm infants. L-thyroxine treatment of preterm newborns: clinical and endocrine effects. Effects of increased thyroxine dosage pre-conception on thyroid function during early pregnancy. Thyroid hormone early adjustment in pregnancy (the THERAPY) trial. A randomized, masked study of triiodothyronine plus thyroxine administration in preterm infants less than 28 weeks of gestational age: hormonal and clinical effects. Thyroid hormone response to moderate hypothermia in severe brain injury. Pulmonary effects of triiodothyronine (T3) and hydrocortisone (HC) supplementation in preterm infants less than 30 weeks gestation: results of the THORN trial--thyroid hormone replacement in neonates. Neurodevelopmental outcomes in congenital hypothyroidism: comparison of initial T4 dose and time to reach target T4 and TSH.
The nature of hypothyroxinemia in sick very low-birth-weight (VLBW) infants was evaluated by assessment of the hypothalamic-pituitary axis and by the clinical response to thyroxine (T4) therapy. Twenty-three very low-birth-weight infants of gestational age 26 to 28 weeks, whose serum T4 concentrations were 4 micrograms/dL on two occasions, and thyrotropin less than 20 microU/mL, were included in a double-blind study. Following a thyrotropin-releasing hormone stimulation test, babies were given either T4 or placebo. Nine babies were thyrotropin-releasing hormone tested prior to therapy; four babies, two from each group, were tested 1 to 2 weeks after therapy. In 11 untreated babies, mean base line serum thyrotropin of 7.0 +/- 1.4 rose to 23.7 +/- 4.1 microU/mL in 30 minutes. This response was not significantly greater than the observed response in full-term babies, 23.7 +/- 4.1 v 16.6 +/- 0.97 microU/mL, respectively, P greater than .05. In two babies treated with T4 the thyrotropin response to thyrotropin-releasing hormone was completely suppressed. Serial serum T4 determinations showed normalization in both groups after a similar time interval. There was no beneficial effect of T4 therapy on growth of head circumference, length, or weight. Developmental data revealed no significant differences in the mental, motor, or gross neurologic outcome in the treated and nontreated infants after 1 year of follow-up. These observations imply that hypothyroxinemia in sick preterm infants is not a direct consequence of hypothyroidism. Despite the lack of demonstrable short-term beneficial effects of T4 therapy, follow-up studies are necessary to resolve the question of long-term benefits. Low levels of circulating thyroid hormones have been associated with poorer general and neurodevelopmental outcome in preterm babies and it has been speculated that the association is causal. Low levels of circulating thyroid hormone have been reported after inadequate intake of iodine in preterm infants being fed milk formula.
                To investigate whether increased iodine intake from supplemented preterm formula would improve thyroid hormone levels in preterm babies (this study) and hence improve neurodevelopmental status (planned subsequent study).
                A total of 121 preterm infants were entered into a randomised controlled trial of standard (68 microg/l) versus increased (272 microg/l) iodine in preterm formula.
                The two groups were comparable at recruitment. No evidence of an effect of the intervention on thyroid hormone levels was seen up to 41 weeks after conception.
                Calls for increased iodine content of preterm infant formulas are not justified by this study. Preterm newborns have low serum thyroxine (T4) levels compared with late-gestational fetuses. Low thyroid hormone levels are associated with increased severity of neonatal illness and neurodevelopmental dysfunction. We assessed the endocrine and clinical effects of increasing serum T4 levels in preterm newborns with a gestational age <31 wk. Forty newborns were randomized in a double blind protocol: 20 infants received a daily dose of 20 microg/kg L-T4 for 2 wk, whereas 20 control infants received saline. Serum concentrations of T4, triiodothyronine (T3), reverse T3 (rT3), thyroglobulin (TG), and TSH were measured weekly as well as serum levels of GH, prolactin, and IGF-I. After 2 wk, a TSH-releasing hormone (TRH) test was performed. Neonatal illness and outcome was evaluated by noting heart rate, oxygen requirement, duration of ventilation, development of chronic lung disease, oral fluid intake, and weight gain; a Bayley score was done at the corrected age of 7 mo. L-T4 administration induced a marked increase in serum T4 without apparent change in T3 levels, whereas the postnatal decline in serum rT3 was more gradual. L-T4 treatment was associated with a decrease in serum TG and TSH levels. TRH injection induced a definite rise in serum TSH and T3 in controls, but not in L-T4 treated newborns. Neither L-T4 treatment, nor TRH administration appeared to alter circulating levels of prolactin, GH, or IGF-I. In contrast to the pronounced endocrine effects, no clinical effects of L-T4 administration were detected. To compare the effects of pregnancy on the serum free thyroxine (FT4) levels in two cohorts of primary hypothyroid women treated with different levothyroxine (L-T4) doses before gestation.
                Twenty-five women with compensated hypothyroidism of different aetiology (thyroidectomized and Hashimoto's thyroiditis) were enrolled in this prospective study. The women were receiving substitutive doses of L-T4 and were anticipating pregnancy. They were assigned to two groups: 14 patients (group I) were switched to partially suppressive treatment while 11 patients (group II) continued the same therapeutic regimen.
                Pre-conceptional thyroid function evaluation demonstrated significantly higher FT4 and lower TSH in group I (P<0.001, for both hormones) and comparable free 3,5,3'-triiodothyronine (FT3) levels. The first post-conception thyroid function evaluation occurred at a median time of 6 (5-8) and 7 (5-9) weeks of gestation, for groups I and II respectively (P<0.05); all women in group I showed adequate serum FT4 levels while three patients in group II showed low-normal FT4 levels and one case was below normal levels. Statistical analysis demonstrated significantly higher frequencies (0% vs 36.4%; P<0.05) of low-normal FT4 levels in patients receiving substitutive doses of L-T4. None of the Hashimoto's-affected patients showed low or low-normal serum FT4 levels regardless of their therapeutic regimen.
                Our results suggest that in hypothyroid women anticipating pregnancy (with serum TSH in the lower quartile of normal range), the pre-conception adjustment of L-T4 doses may result in adequate maternal thyroid function up to the first post-conception evaluation. The procedure seems safe and inexpensive; it may be a worthwhile treatment, at least in thyroidectomized women, in view of the well-known potential effects of even marginal maternal thyroid hypofunction on the subsequent IQ of the progeny. Thyroid hormone requirement increases 20-40% during gestation. Women with treated hypothyroidism must increase their l-T(4) in pregnancy to prevent maternal hypothyroidism, although how this should be accomplished is unclear.
                We prospectively enrolled 60 women with treated hypothyroidism seeking pregnancy. Once pregnant, women were randomized to increase l-T(4) by either two tablets/wk (group A) or three tablets/wk (group B). Thyroid function was tested biweekly through midpregnancy and at 30 wk gestation. Levothyroxine was adjusted to maintain goal TSH concentrations. The primary objective was to assess efficacy in preventing maternal hypothyroidism and the safety of this intervention.
                Forty-eight women completed the protocol. Increasing the l-T(4) dose once pregnant (regardless of study arm) prevented TSH elevation over 5.0 mIU/liter throughout the first trimester and replicated physiological changes of pregnancy. The early l-T(4) increase caused TSH suppression below 0.5 mIU/liter in eight of 25 women in group A compared with 15 of 23 women in group B (P < 0.01). This risk was significantly increased in athyreotic patients [odds ratio (OR) = 3.3; 95% confidence interval (CI) = 1.1-11.1], those with prepregnancy TSH less than 1.5 mIU/liter (OR = 4.6; 1.3-16.2), and those receiving prepregnancy l-T(4) doses of 100 microg/d or more (OR = 7.2; 1.7-30.6). However, if a trimester-specific TSH lower reference range of 0.1 mIU/liter was used, only two patients (8%) in group A required dose reduction. TSH testing every 4 wk identifies 92% of abnormal values.
                A two-tablet increase in l-T(4) initiated at confirmation of pregnancy significantly reduces the risk of maternal hypothyroidism during the first trimester and mimics normal physiology. Monitoring TSH every 4 wk through midgestation is recommended. 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. To examine the effect of controlled moderate hypothermia on thyroid response in head-injured patients.
                Prospective, controlled, randomized study.
                University hospital intensive care unit (ICU).
                Twenty-eight patients with severe blunt head injury (Glasgow Coma Scale < or =9).
                Patients were randomly assigned to a hypothermia or a normothermia group. Hypothermia (32-33 degrees C) was induced within 8 h after trauma and maintained for a mean of 36 h. All patients were sedated and mechanically ventilated.
                Thyroid-stimulating hormone( TSH), free and total triiodothyronine (FT3/TT3), reverse triiodothyronine (RT3) and thyroxine (FT4/TT4) were measured during the hypothermia or corresponding normothermia period, after regaining normothermia and 4-6 days later. Of 28 patients included in the study, 11 subjects were treated with hypothermia and 13 patients with normothermia. Four patients had to be excluded. In both groups, serum concentrations of TT3 and FT3 were just below the lower normal range whereas RT3 serum concentrations were near the upper limit of the normal range. TSH serum concentrations were not increased. No statistically significant intra- or inter-group differences were observed.
                Thyroid hormone patterns during moderate hypothermia in head-injured patients did not differ from the well known "low T3 state" which is observed in other forms of severe illness. The THORN trial was a multicenter, randomized, double-blind, placebo-controlled clinical trial to test the hypothesis that administration of triiodothyronine (T(3)) and hydrocortisone would decrease mortality and respiratory morbidity in preterm infants of less than 30 wk gestation. Two hundred fifty-three infants were randomized to receive either 6 micro g.kg(-1).d(-1) of T(3) with 1 mg.kg(-1).d(-1) of hydrocortisone or 5% dextrose (placebo) as a continuous i.v. infusion for 7 d. The dose was halved on d 5. Our first primary outcome was death or ventilator dependence at 1 wk, and the second was death or oxygen dependence at 2 wk. The overall mortality rate for both groups was 11.4%. Relative risk of death or ventilator dependence at 1 wk, treated versus placebo, was 0.87, p = 0.2, and death or oxygen dependence at 2 wk, 1.00, p = 0.9. We examined the relationship between free T(3) (FT(3)) and free thyroxine (FT(4)) levels in the first 7 d and the primary outcome death or ventilator dependence at 1 wk in all 253 babies. We found significant positive correlations of p = 0.05 for FT(3) and p = 0.002 for FT(4). Thus the higher the FT(3) and FT(4) levels, the better the outcome. No beneficial effects of T(3) and hydrocortisone were shown. In this study, although FT(3) levels were doubled by the treatment infusion, FT(4) levels were significantly suppressed. The lack of any beneficial effect of T(3) in our study may be explained by suppression of FT(4) in the treatment group. To compare neurodevelopmental outcomes in severe and moderate congenital hypothyroidism (CH) among 3 different initial L-thyroxine doses and to examine the effect of the time to thyroid function normalization on neurodevelopmental outcomes.
                Neurodevelopmental assessments of 31 subjects included the Mullen Scales of Early Learning, Wechsler Preschool and Primary Scale of Intelligence-Revised, Wechsler Intelligence Scale for Children, Wide-Range Achievement Test, and Child Behavioral Checklist.
                Subjects started on higher initial L-thyroxine doses (50 mug) had full-scale IQ scores 11 points higher than those started on lower (37.5 mug) initial doses. However, verbal IQ, performance IQ, and achievement scores did not differ among the 3 treatment cohorts. Subjects with moderate CH had higher full-scale IQ scores than subjects with severe CH, regardless of the initial treatment dose. Subjects who took longer than 2 weeks to normalize thyroid function had significantly lower cognitive, attention, and achievement scores than those who achieved normal thyroid function at 1 or 2 weeks of therapy.
                Initial L-thyroxine dose and faster time to normalization of thyroid function are important to optimal neurodevelopmental outcome. In severe CH, it is important to choose an initial dose at the higher end of the recommended range to achieve these goals.
There is insufficient evidence to determine whether use of thyroid hormones for treatment of preterm infants with transient hypothyroxinaemia results in changes in neonatal morbidity and mortality, or reductions in neurodevelopmental impairments. Further research is required.