Early Pregnancy Reference Intervals of Thyroid Hormone Concentrations in a Thyroid Antibody-Negative Pregnant Population

Männistö, Tuija; Surcel, Heljä‐Marja; Ruokonen, Aimo; Vääräsmäki, Marja; Pouta, Anneli; Bloigu, Aini; Järvelin, Marjo‐Riitta; Hartikainen, Anna-Liisa; Suvanto, Eila

doi:10.1089/thy.2010.0337

Cited by 134 publications

(103 citation statements)

References 36 publications

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“…In that study, BMI averaged 2.9 kg/m 2 higher (17 lb) in association with FT4 concentrations below the 2.5th centile. Other recent studies have documented similar relationships (4)(5)(6)(7). Depending upon the nature of this relationship across the broader BMI or weight spectrum, a maternal weight effect might partially explain variations among individual FT4 ranges, thereby accounting for a portion of overall population variability.…”

Section: Introductionmentioning

confidence: 57%

Impact of Adjusting for the Reciprocal Relationship Between Maternal Weight and Free Thyroxine During Early Pregnancy

Haddow

Craig

Palomaki

et al. 2013

Thyroid

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for the First and Second Trimester Risk of Aneuploidy (FaSTER) Research ConsortiumBackground: Among euthyroid pregnant women in a large clinical trial, free thyroxine (FT4) measurements below the 2.5th centile were associated with a 17 lb higher weight (2.9 kg/m 2 ) than in the overall study population. We explore this relationship further. Methods: Among 9351 women with second trimester thyrotropin (TSH) measurements between 1st and 98th centiles, we examine: (i) the weight/FT4 relationship; (ii) percentages of women in three weight categories at each FT4 decile; (iii) FT4 concentrations in three weight categories at each TSH decile; and (iv) impact of adjusting FT4 for weight-in the reference group and in 190 additional women with elevated TSH measurements. Results: FT4 values decrease steadily as weight increases ( p < 0.0001 by ANOVA) among women in the reference group (TSH 0.05-3.8 IU/L). TSH follows no consistent pattern with weight. When stratified into weight tertiles, 48% of women at the lowest FT4 decile are heavy; the percentage decreases steadily to 22% at the highest FT4 decile. Median FT4 is lowest in heaviest women regardless of the TSH level. In the reference group, weight adjustment reduces overall variance by 2.9%. Fewer FT4 measurements are at either extreme (below the 5th FT4 centile: 4.8% before adjustment, 4.7% after adjustment; above the 95th FT4 centile: 5.0% and 4.7%, respectively). Adjustment places more light weight women and fewer heavy women below the 5th FT4 centile; the converse above the 95th centile. Between TSH 3.8 and 5 IU/L, the FT4 percentage below the 5th FT4 centile is not elevated (3.8% before adjustment, 3.1% after adjustment). Percentage of FT4 values above the 95th centile, however, is lower (1.5% before adjustment, 0.8% after adjustment). Above TSH 5 IU/L, 25% of women have FT4 values below the 5th FT4 centile; weight adjustment raises this to 30%; no FT4 values remain above the 95th FT4 centile. Conclusions: During early pregnancy, TSH values are not associated with weight, unlike nonpregnant adults. Lower average FT4 values among heavy women at all TSH deciles partially explain interindividual differences in FT4 reference ranges. The continuous reciprocal relationship between weight and FT4 explains lower FT4 with higher weight. Weight adjustment refines FT4 interpretation.

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Section: Introductionmentioning

confidence: 57%

Impact of Adjusting for the Reciprocal Relationship Between Maternal Weight and Free Thyroxine During Early Pregnancy

Haddow

Craig

Palomaki

et al. 2013

Thyroid

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“…2 and Table 1), and both median TSH and upper and lower reference limits start decreasing (32,33,34,35,36). To emphasize that thyroid function test reference values are variable in pregnancy, but still keep evaluation somewhat simple, much focus has been Early pregnancy variation in test result in a woman who has no functional thyroid gland, but who was euthyroid on levothyroxine replacement therapy before becoming pregnant.…”

Section: Changes In Thyroid Function and Test Reference Limits In Prementioning

confidence: 99%

ENDOCRINOLOGY IN PREGNANCY: Pregnancy and the incidence, diagnosing and therapy of Graves’ disease

Laurberg

Andersen

2016

European Journal of Endocrinology

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Thyroid hormones are essential developmental factors, and Graves' disease (GD) may severely complicate a pregnancy. This review describes how pregnancy changes the risk of developing GD, how early pregnancy by several mechanisms leads to considerable changes in the results of the thyroid function tests used to diagnose hyperthyroidism, and how these changes may complicate the diagnosing of GD. Standard therapy of GD in pregnancy is anti-thyroid drugs. However, new studies have shown considerable risk of birth defects if these drugs are used in specific weeks of early pregnancy, and this should be taken into consideration when planning therapy and control of women who may in the future become pregnant. Early pregnancy is a period of major focus in GD, where pregnancy should be diagnosed as soon as possible, and where important and instant change in therapy may be warranted. Such change may be an immediate stop of anti-thyroid drug therapy in patients with a low risk of rapid relapse of hyperthyroidism, or it may be an immediate shift from methimazole/carbimazole (with risk of severe birth defects) to propylthiouracil (with less risk), or maybe to other types of therapy where no risk of birth defects have been observed. In the second half of pregnancy, an important concern is that not only the mother with GD but also her foetus should have normal thyroid function.Thyroid hormones are essential developmental factors as first shown by Gudernatsch when he, in 1912, fed tadpoles thyroid tissue and observed metamorphosis (1). In mammals, thyroid hormones are especially of importance for brain development (2, 3), and even a few months with lack of thyroid hormones in infant life may lead to irreversible brain damage. This is the background for the universal screening for congenital hypothyroidism performed in many countries. However, thyroid hormones are also important for normal pregnancy, and maternal thyroid disease may severely increase the risk of pregnancy complications, including Invited author's profile Peter Laurberg was Clinical Professor of Internal Medicine and Endocrinology, Department of Endocrinology, Aalborg University Hospital, Aalborg, Denmark. His research mainly focused on thyroid disease prevention, epidemiology, diagnosing and therapy, including studies on iodine and thyroid, and pregnancy and thyroid. He had special research interest on the risk from and optimal management of autoimmune hypo-and hyperthyroidism in pregnancy and post-partum, management of Graves' disease in general, and how the burden of thyroid disease can be minimized by adjusting the population's iodine intake. He has coauthored several international guidelines on thyroid disease management, including management of thyrotoxicosis, and thyroid disease in pregnancy. Peter Laurberg died June 20, 2016.

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“…In the near future, tandem mass spectrometry, which has shown a very good correlation with equilibrium dialysis during gestation (76), may be the technique to be used for such purposes. Another factor to consider during pregnancy is the observed inverse relationship between FT 4 and weight (127,128). In this regard, the recent work of Medici et al (129) has shown a decrease in the weight of children born to mothers with FT 4 in the upper limit of normality.…”

Section: European Journal Of Endocrinologymentioning

confidence: 99%

CONTROVERSIES IN ENDOCRINOLOGY: On the need for universal thyroid screening in pregnant women

Vila

Velasco

González

et al. 2014

European Journal of Endocrinology

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There is a well-known controversy among scientific societies regarding the recommendation to screen for thyroid dysfunction (TD) during pregnancy. Although several studies have shown an association between maternal subclinical hypothyroidism and/or hypothyroxinemia with obstetric problems and/or neurocognitive impairment in the offspring, there is only limited evidence on the possible positive effects of thyroxine (T 4 ) treatment in such cases. Despite the scarcity of this evidence, there is a widespread agreement among clinicians on the need for treatment of clinical hypothyroidism during pregnancy and the risks that could arise due to therapeutic abstention. As maternal TD is a quite prevalent condition, easily diagnosed and for which an effective and safe treatment is available, some scientific societies have proposed to assess thyroid function during the first trimester of pregnancy and ideally before week 10 of gestational age. Given the physiologic changes of thyroid function during pregnancy, hormone assessment should be performed using trimester-specific reference values ideally based on locally generated data as geographic variations have been detected. Screening of TD should be based on an initial determination of TSH performed early during the first trimester and only if abnormal should it be followed by either a free or total T 4 measurement. Furthermore, adequate iodine supplementation during pregnancy is critical and if feasible it should be initiated before the woman attempts to conceive.

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Early Pregnancy Reference Intervals of Thyroid Hormone Concentrations in a Thyroid Antibody-Negative Pregnant Population

Abstract: These gestational age-specific reference intervals for thyroid hormones provide a framework for clinical decision making. Overweight and obesity are increasing problems among fertile women and they are associated with possibility of thyroid dysfunction during pregnancy.

Cited by 134 publications

References 36 publications

Impact of Adjusting for the Reciprocal Relationship Between Maternal Weight and Free Thyroxine During Early Pregnancy

Impact of Adjusting for the Reciprocal Relationship Between Maternal Weight and Free Thyroxine During Early Pregnancy

ENDOCRINOLOGY IN PREGNANCY: Pregnancy and the incidence, diagnosing and therapy of Graves’ disease

CONTROVERSIES IN ENDOCRINOLOGY: On the need for universal thyroid screening in pregnant women

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