FT4 immunoassays may display a pattern during pregnancy similar to the equilibrium dialysis ID–LC/tandem MS candidate reference measurement procedure in spite of susceptibility towards binding protein alterations

Anckaert, Ellen; Poppe, Kris; Uytfanghe, Katleen Van; Schiettecatte, Johan; Foulon, Walter; Thienpont, Linda M.

doi:10.1016/j.cca.2010.05.032

Cited by 77 publications

(41 citation statements)

References 29 publications

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“…In order to decrease nonspecific binding and neutralize the effect of nonesterified fatty acids on serum FT 4 , some assays add albumin; however, albumin binds T 4 and when it is added in sufficient amounts, it may disrupt the equilibrium. Nevertheless, the currently used FT 4 immunoassays perform reasonably well under most circumstances, accurately reporting low FT 4 levels in thyroid hormone deficiency and high FT 4 levels in thyroid hormone excess (27).The serum of pregnant women is characterized by higher concentrations of TBG and nonesterified fatty acids and by lower concentrations of albumin relative to the serum of nonpregnant women. Many current FT 4 immunoassays fail to account for the effect of dilution (26,28).…”

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2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

Alexander

Pearce

Brent

et al. 2017

Thyroid

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INTRODUCTION Pregnancy has a profound impact on the thyroid gland and thyroid function. The gland increases 10% in size during pregnancy in iodine-replete countries and by 20%-40% in areas of iodine deficiency. Production of thyroxine (T 4 ) and triiodothyronine (T 3 ) increases by 50%, along with a 50% increase in the daily iodine requirement. These physiological changes may result in hypothyroidism in the later stages of pregnancy in iodine-deficient women who were euthyroid in the first trimester. The range of thyrotropin (TSH), under the impact of placental human chorionic gonadotropin (hCG), is decreased throughout pregnancy with the lower normal TSH level in the first trimester being poorly defined and an upper limit of 2.5 mIU/L. Ten percent to 20% of all pregnant women in the first trimester of pregnancy are thyroid peroxidase (TPO) or thyroglobulin (Tg) antibody positive and euthyroid. Sixteen percent of the women who are euthyroid and positive for TPO or Tg antibody in the first trimester will develop a TSH that exceeds 4.0 mIU/L by the third trimester, and 33%-50% of women who are positive for TPO or Tg antibody in the first trimester will develop postpartum thyroiditis. In essence, pregnancy is a stress test for the thyroid, resulting in hypothyroidism in women with limited thyroidal reserve or iodine deficiency, and postpartum thyroiditis in women with underlying Hashimoto's disease who were euthyroid prior to conception.Knowledge regarding the interaction between the thyroid and pregnancy/the postpartum period is advancing at a rapid pace. Only recently has a TSH of 2.5 mIU/L been accepted as the upper limit of normal for TSH in the first trimester. This has important implications in regards to interpretation of the literature as well as a critical impact for the clinical diagnosis of hypothyroidism. Although it is well accepted that overt hypothyroidism and overt hyperthyroidism have a deleterious impact on pregnancy, studies are now focusing on the potential impact of subclinical hypothyroidism and subclinical hyperthyroidism on maternal and fetal health, the association between miscarriage and preterm delivery in euthyroid women positive for TPO and/or Tg antibody, and the prevalence and long-term impact of postpartum thyroiditis. Recently completed prospective randomized studies have begun to produce critically needed data on the impact of treating thyroid disease on the mother, fetus, and the future intellect of the unborn child.It is in this context that the American Thyroid Association (ATA) charged a task force with developing clinical guidelines on the diagnosis and treatment of thyroid disease during pregnancy and the postpartum. The task force consisted of international experts in the field of thyroid disease and pregnancy, and included representatives from the ATA, Asia and Oceania Thyroid Association, Latin American Thyroid Society, American College of Obstetricians and Gynecologists, and the Midwives Alliance of North America. Inclusion of thyroidologists, obstetricians, and midwives ...

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confidence: 99%

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

Alexander

Pearce

Brent

et al. 2017

Thyroid

1,903

2,716

View full text Add to dashboard Cite

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“…Inconsistency in test combinations used by the responders (Table 2) for monitoring anti thyroid drugs' doses during pregnancy may to some extent be due to the availability of tests in different settings. On the other hand, despite the controversy on the accuracy of FT4 assays during pregnancy about 82% of physicians used FT4 alone or in combination with other tests [25,26].…”

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Management of hyperthyroidism during pregnancy in Asia

et al. 2014

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“…This has been previously reported [1] and was interpreted either as a spurious measurement due to unreliable FT4 assay in pregnancy [23] , or as hypothyroxinemia, considered 'pathological' and possibly linked to ID [2] . We used a chemiluminescence assay that was shown to be reliable in pregnancy when compared to the direct equilibrium dialysis method coupled to mass spectrometry which is considered as the gold standard for FT4 measurement during and outside pregnancy [24] . As recently reviewed by Zimmerman [25] , in the controlled trials with a similar design (with a supplementation from 100 to 230 μg/day) conducted in mild to moderately iodine-deficient pregnant women, there was no difference in maternal thyroxine levels between iodine-supplemented and control groups [10,14,[16][17][18] .…”

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Iodine Supplementation throughout Pregnancy Does Not Prevent the Drop in FT4 in the Second and Third Trimesters in Women with Normal Initial Thyroid Function

et al. 2013

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the control group. In the cross-sectional study, there was no difference between the two groups in thyroid tests at any time-point, except for lower Tg in the second trimester and postpartum visits in the iodine group. Conclusions: In healthy, mildly iodine-deficient pregnant women, a 'drop' of FT4 and TT4/TBG without TSH increase occurs between the first and second trimesters, and is not prevented by iodine supplementation, suggesting physiology. Therefore, FT4 is valuable to assess thyroid function in pregnancy in clinical practice with appropriate trimester-specific reference range. It brings up reflection on threshold for diagnosis and treatment of hypothyroxinemia.

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FT4 immunoassays may display a pattern during pregnancy similar to the equilibrium dialysis ID–LC/tandem MS candidate reference measurement procedure in spite of susceptibility towards binding protein alterations

Cited by 77 publications

References 29 publications

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

Management of hyperthyroidism during pregnancy in Asia

Iodine Supplementation throughout Pregnancy Does Not Prevent the Drop in FT4 in the Second and Third Trimesters in Women with Normal Initial Thyroid Function

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