Subclinical Hypothyroidism and Pregnancy Outcomes

Casey, Brian M.; Dashe, Jodi S.; Wells, C. Edward; McIntire, Donald D.; Byrd, William E.; Leveno, Kenneth J.; Cunningham, F. Gary

doi:10.1097/01.aog.0000152345.99421.22

Cited by 784 publications

(625 citation statements)

References 18 publications

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“…[4][5][6] Normal thyroid hormone levels promote normal growth and development in the fetus and prematurely born neonates. [7][8][9][10][11] The data provided in this article are taken from a randomized, double-blind clinical trial, which examined whether increased intravenous amino-acid supplementation would improve growth. In this trial, it was hypothesized that increased amino-acid supplementation would improve growth and well being and that normalization of serum amino acids would increase thyroxine levels.…”

Section: Introductionmentioning

confidence: 99%

The influence of amino-acid supplementation, gestational age and time on thyroxine levels in premature neonates

Kelleher¹,

Clark²,

Steinbach³

et al. 2008

J Perinatol

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Objective: Newborn screening laboratories vary in the values that are used to define congenital hypothyroidism. Defining congenital hypothyroidism is particularly complex in premature neonates because prematurely born infants often have a low free thyroxine value and low or normal TSH value, termed as transient hypothyroxinemia of prematurity. In a multicenter (n ¼ 11 sites) trial, we randomly allocated premature neonates with a gestational age of 23 to 29 and 6/7 weeks to one of two parenteral nutrition approaches. The primary objective of our trial was to measure the effect of two distinct strategies of parenteral nutrition on neonatal growth and blood amino acids. A protocol defined secondary aim of our clinical trial was the evaluation of the influence of gestational age, time and the degree of amino-acid supplementation on total thyroxine levels. We hypothesized that an increase of amino-acid supplementation would be associated with the normalization of serum amino acids and that this would improve thyroxine synthesis.Study Design: Premature neonates (23 to 29 and 6/7 weeks) were randomly allocated to one of two approaches to intravenous amino-acid administration. In one group, amino-acid supplementation started at 1.0 g kg À1 per day and advanced by 0.5 g kg À1 per day to a maximum of 2.5 g kg À1 per day (2.5 group). The other group received amino acids at 1.5 g kg À1 per day and advanced by 1.0 g kg À1 per day to a maximum of 3.5 g kg À1 per day (3.5 group). Filter paper blood spots were obtained on the day of randomization, and on days 7 and 28 of age to monitor laboratory values.Result: Enrollment included 122 neonates, 64 in the 3.5 group and 58 in the 2.5 group. There were no differences in demographics or baseline characteristics between the two treatment groups. There were no significant differences in thyroid levels at baseline, on days 7 and 28 between the two treatment groups. Growth was similar in both groups. It was noted that thyroxine levels changed over time and that the changes with time were greatest in the most preterm neonates. Conclusion:The degree of amino-acid supplementation does not influence thyroxine levels and both time from birth and gestational age do influence thyroxine levels.

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Section: Introductionmentioning

confidence: 99%

The influence of amino-acid supplementation, gestational age and time on thyroxine levels in premature neonates

Kelleher¹,

Clark²,

Steinbach³

et al. 2008

J Perinatol

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“…Prevalence rates are similar during pregnancy [2,5]. Three large studies have assessed the prevalence of hypothyroidism in pregnant women.…”

Section: Epidemiologymentioning

confidence: 99%

“…The severity, timing of onset and duration, as well as postnatal management, all influence fetal and neonatal brain development. It is now believed than even mild maternal hypothyroidism (from mild iodine deficiency, thyroid autoimmunity, or thyroid under-replacement) may affect fetal brain development [5,6] Adequate thyroid hormone is critical for cerebellar development. Developmental hypothyroidism induced by iodine deficiency during the perinatal period results in permanent impairments of cerebellar development with an unclear mechanism [52].…”

Section: Influence Of Maternal Thyroid Disease On Fetal Developmentmentioning

confidence: 99%

“…It is now well established that OH is associated with an increased risk of adverse pregnancy complications, as well as detrimental effects upon fetal neurocognitive development [4]. However, data regarding SCH are controversial [4,5] In the past several years, there has been a debate about the universal screening of thyroid disorders. There is until now insufficient evidence to recommend for or against evaluating thyroid function in all pregnant women.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

11 Hypothyroidism in Pregnancy

Lazarus¹,

Pīrāgs²,

Butz³

2009

The Thyroid and Reproduction

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“…The study can only answer what to expect concerning development of thyroid function tests if you choose to treat women with different concentrations of serum TSH. That does not, however, indicate whether or not the treatment was beneficial since no control group was included and no outcome variables of pregnancy or neurocognitive development of the baby were included [6,7].…”

mentioning

confidence: 99%

Subclinical hypothyroidism in pregnancy: to treat or not to treat

Feldt‐Rasmussen

2013

Endocrine

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The published study [1] aimed to observe the pattern of thyroid function in pregnant women with subclinical hypothyroidism treated with levothyroxine (LT4) throughout pregnancy and to obtain the optimal dosages of LT4 for pregnant women with subclinical hypothyroidism. The authors screened 4,102 pregnant women from 10 hospitals of the Shenyang region, northeast China, and enrolled 89 women among 938 with subclinical hypothyroidism defined by serum thyrotropin [2.5 mU/L and ''normal'' free thyroxine (T4), but ended by including 56 compliant women. They were divided in three groups based on different serum TSH concentrations, given three different dosages of LT4 and followed with 4-week intervals by measuring thyroid function tests until week 36 of gestation. Ten of the patients had to be dose adjusted to remain within target, the others stayed on the same dose.The authors conclude that different LT4 doses can be chosen according to the baseline TSH levels of pregnant women, and maintain serum TSH levels of 79.3-90 % patients in the ideal range. 20 % need adjustment of therapy during second and third trimester. Careful monitoring of serum TSH and free T4 each month is, therefore, advocated.The study is thus a small descriptive contribution to demonstrating the biochemical pattern during different LT4 dosages during pregnancy of women with subclinical hypothyroidism. However, the study leaves a lot of caveats and unanswered questions.In 2011, the ATA guidelines [2] mentioned that subclinical hypothyroidism has been associated with adverse maternal and fetal outcomes, and recommended that women with positive antibodies against thyroid peroxidase or thyroglobulin and subclinical hypothyroidism should be treated with LT4. The same guidelines also recommended LT4 replacement in women with antibody negative subclinical hypothyroidism, although the evidence levels were very low both for obstetrical and neonatal neurological outcome. The current study [1] does not mention any measurement of thyroid antibodies, and the etiology of subclinical hypothyroidism is, therefore, quite unclear; the study does not include an untreated control group, which would have been advantageous for comparison of the biochemical evolution of the thyroid function tests, considering in particular that serum TSH is very often lowered in early pregnancy due to an effect from human chorionic gonadotropin [3]; the study does mention the use of trimester-specific reference concentrations for serum TSH and free T4, but do not take into account the high degree of intraindividual variation of the concentrations, even in pregnancy [4]; the strict cut-off concentrations necessary for conducting the study are very dependent on method and laboratory [5], which should have been discussed in the paper. Even though the study mentions cut-off concentrations for TSH and free T4, the authors do not mention, how many were outside target in each method, which would have been useful information for the clinician.One of the important points for discussion within this...

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Subclinical Hypothyroidism and Pregnancy Outcomes

Abstract: II-2.

Cited by 784 publications

References 18 publications

The influence of amino-acid supplementation, gestational age and time on thyroxine levels in premature neonates

The influence of amino-acid supplementation, gestational age and time on thyroxine levels in premature neonates

11 Hypothyroidism in Pregnancy

Subclinical hypothyroidism in pregnancy: to treat or not to treat

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