Reference Values for Thyroid Function Tests in Pregnant Women Living in Catalonia, Spain

Vila, Lluís; Serra‐Prat, Mateu; Palomera, Elísabet; Casamitjana, Roser; Castro, Alfonso; Legaz, Gustavo; Barrionuevo, Celia; García, A. M. Bonilla; Lal-Trehan, Sanjay; Muñoz, J.; Durán, Josep; García, A Luz Vargas; Puig-Domingo, Manel

doi:10.1089/thy.2008.0264

Cited by 40 publications

(17 citation statements)

References 28 publications

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“…Although misclassification of depressed young females as cases of hyperthyroidism would have attenuated any radiation dose-response in this gender group, the extent of such misclassification is probably small. Serum TSH levels also decrease during the late first trimester of pregnancy (2, 37). Females in our sample, many of child-bearing age, were not asked whether they were pregnant at the time of the screening examination when blood samples were drawn for measurement of TSH and other thyroid hormones.…”

Section: Discussionmentioning

confidence: 99%

Prevalence of Hyperthyroidism after Exposure during Childhood or Adolescence to Radioiodines from the Chornobyl Nuclear Accident: Dose–Response Results from the Ukrainian-American Cohort Study

et al. 2010

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Relatively few data are available on the prevalence of hyperthyroidism (TSH concentrations of < 0.3 mIU/L, with normal or elevated concentrations of free T4) in individuals exposed to radioiodines at low levels. The accident at the Chornobyl (Chernobyl) nuclear plant in Ukraine on April 26, 1986 exposed large numbers of residents to radioactive fallout, principally to iodine-131 (I-131) (mean and median doses = 0.6 Gray (Gy) and 0.2 Gy). We investigated the relationship of I-131 and prevalent hyperthyroidism among 11,853 individuals exposed as children or adolescents in Ukraine who underwent an in-depth, standardized thyroid gland screening examination 12–14 years later. Radioactivity measurements taken shortly after the accident were available for all subjects and were used to estimate individual thyroid doses. We identified 76 cases of hyperthyroidism (11 overt, 65 subclinical). Using logistic regression, we tested a variety of continuous risk models and conducted categorical analyses for all subjects combined and for females (53 cases, n=5,767) and males (23 cases, n=6,086) separately, but found no convincing evidence of a dose response relationship between I-131 and hyperthyroidism. There was some suggestion of elevated risk among females in an analysis based on a dichotomous dose model with a threshold of 0.5 Gy chosen empirically (OR=1.86, P=0.06), but the statistical significance level was reduced (P=0.13) in a formal analysis with an estimated threshold. In summary, after a thorough exploration of the data, we found no statistically significant dose response relationship between individual I-131 thyroid doses and prevalent hyperthyroidism.

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Section: Discussionmentioning

confidence: 99%

Prevalence of Hyperthyroidism after Exposure during Childhood or Adolescence to Radioiodines from the Chornobyl Nuclear Accident: Dose–Response Results from the Ukrainian-American Cohort Study

et al. 2010

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“…FT 4 index (FT 4 I) is a calculated ratio based on two estimates, namely an estimate of triiodothyronine (T 3 ) resin uptake and an immunoassay Given the significant changes in the concentrations of thyroid hormones throughout gestation (80), the ATA has recommended that the formulation of the reference values should be performed not only for each trimester of pregnancy but also for each specific geographical region (81) and probably also taking into account the importance of potential variations between the technical methods of measurement. In Spain, for example, different regional studies have been performed (43,82,83,84) aiming to determine the reference range for thyroid hormones in pregnant women. The recent ATA guideline recommends that in the absence of local reference values, the upper normal value for TSH in pregnant women should be 2.5 mUI/ml in the first trimester and 3 mUI/ml in the second and third trimesters.…”

Section: Obstetric Complications Associated With Td "mentioning

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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“…This, however, was a combination of cross-sectional samples as well as longitudinal samples from the same patients. 18 In 2010, Yu et al 19 calculated longitudinal reference intervals in the Chinese population and demonstrated narrower intervals compared to other studies. Cotzias et al in 2007 also reported cross-sectional reference intervals.…”

Section: Introductionmentioning

confidence: 98%

Establishing trimester-specific maternal thyroid function reference intervals

et al. 2013

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Background: Thyroid disorders are common in women of childbearing age and are associated with adverse pregnancy outcomes. Physiological changes in pregnancy and the lack of pregnancy-specific reference ranges make managing thyroid disorders in pregnancy challenging. Our aim was to establish trimester-specific thyroid function reference intervals throughout pregnancy, and to examine the prevalence of thyroid autoimmunity in otherwise euthyroid women. Method: This was a prospective, cross-sectional study of thyroid function tests (TFTs) in pregnant women attending a large, tertiary referral maternity hospital. Patients with known thyroid disorders, autoimmune disease, recurrent miscarriage, hyperemesis gravidarum and pre-eclampsia were excluded. TFTs were analysed in the CUH biochemistry laboratory using Roche Modular E170 electrochemiluminescent immunoassay. Trimester-specific reference ranges (2.5th, 50th and 97.5th centiles) were calculated. Results: Three-hundred-and-fifty-one women were included into the analysis. Median maternal age was 30. Thyroidstimulating hormone concentrations showed slightly increasing median centile throughout gestation. Free thyroxine (T4) and T3 decreased throughout gestation. Table 1 demonstrates the calculated percentiles according to gestational weeks. Conclusion: We established pregnancy-specific thyroid function reference intervals for our pregnant population, for use in clinical practice.

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Reference Values for Thyroid Function Tests in Pregnant Women Living in Catalonia, Spain

Cited by 40 publications

References 28 publications

Prevalence of Hyperthyroidism after Exposure during Childhood or Adolescence to Radioiodines from the Chornobyl Nuclear Accident: Dose–Response Results from the Ukrainian-American Cohort Study

Prevalence of Hyperthyroidism after Exposure during Childhood or Adolescence to Radioiodines from the Chornobyl Nuclear Accident: Dose–Response Results from the Ukrainian-American Cohort Study

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

Establishing trimester-specific maternal thyroid function reference intervals

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