Value of Combined Clinical Information and Thyroid Peroxidase Antibodies in Pregnancy for the Prediction of Postpartum Thyroid Dysfunction

Associations between phthalate exposure and thyroid function in pregnant women during the first trimester

Phthalates are a class of environmental endocrine disruptors. Previous studies have demonstrated that phthalate exposure can affect thyroid function; however, limited studies have assessed the associations between phthalate exposure and thyroid function, especially thyroid autoimmunity in pregnant women during the first trimester. We recruited participants from a cohort of pregnant women in Beijing, China, and collected urine samples to measure ten phthalate metabolites, serum samples to measure free thyroxine (FT₄), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb) during the first trimester. We included 325 pregnant women without thyroid diseases or dysfunction in this study. Associations between phthalate metabolites and thyroid function parameters were assessed with the Bayesian kernel machine regression (BKMR) model, multiple linear regression model, and restricted cubic spline. In the BKMR model analysis, compared to the 50th percentile, total urinary phthalate metabolites levels were negatively associated with serum TPOAb levels when phthalate metabolites were at or below the 40th percentile. Stratifying by body mass index, total urinary phthalate metabolites levels were negatively associated with serum TPOAb levels in normal weight women when phthalate metabolites were at or below the 45th percentile. However, total urinary phthalate metabolites levels were positively associated with serum TPOAb levels in underweight women when phthalate metabolites were at or below the 30th percentile. In restricted cubic spline analysis, L-shaped nonlinear associations of mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), di-(2-ethylhexyl) phthalate (ΣDEHP), and inverted S-shaped nonlinear association of mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) with TPOAb were observed. In conclusion, our findings suggest that phthalate exposure may affect thyroid autoimmunity in underweight pregnant women during early pregnancy, and the potential effects of phthalate exposure on thyroid autoimmunity may be nonlinear.

The Clinical Value and Variation of Antithyroid Antibodies during Pregnancy

Antithyroid antibodies, which include thyroid-stimulating hormone receptor antibodies (TRAbs), thyroid peroxidase antibodies (TPOAbs), and thyroid globulin antibodies (TgAbs), are widely known for their tight association with thyroid autoimmune diseases. The variation in all three kinds of antibodies also showed different trends during and after pregnancy (Weetman, 2010). This article reviewed the the physiological changes, while focusing on the variation of thyroid antibodies concentration in women during and after pregnancy, and adverse consequences related to their elevation. Since abnormal elevations of these antithyroid antibodies may lead to adverse outcomes in both mothers and fetuses, special attention must be paid to the titer of the antibodies during pregnancy. The molecular mechanisms of the variations in those antibodies have yet to be explained. The frequency and timing of thyroid antibody measurement, as well as different reference levels, also remain to be elucidated.

Prevalence of thyroid autoimmunity and effect of levothyroxine treatment in a cohort of 1064 patients with recurrent pregnancy loss

RESEARCH QUESTION

Does initiating levothyroxine treatment based on thyroid-stimulating hormone (TSH) >2.5 mIU/l or thyroid autoimmunity improve pregnancy continuation rates in recurrent pregnancy loss (RPL) patients?

DESIGN

A retrospective cohort study of 1064 RPL patients, in which subjects were classified as either euthyroid (TSH 0.1 to ≤2.5 mIU/l), borderline-subclinical hypothyroid (borderline-SCH, TSH 2.5 to ≤4 mIU/l) or subclinical hypothyroid (SCH, TSH 4 to ≤10 mIU/l). For subjects with ≥2 pregnancy losses and a subsequent pregnancy with known outcome, a comparison was done of the pregnancy continuation rate past 10 weeks of treated and untreated borderline-SCH (n = 98) and untreated euthyroid (n = 279) subjects, and between subjects with positive (n = 18) and negative (n = 206) thyroid peroxidase (TPOAb tests) within the borderline-SCH and euthyroid groups.

RESULTS

72.7% were euthyroid (721/992), 19.4% (192/992) were borderline-SCH, and 5.4% (54/992) were subclinically hypothyroid (SCH). Of 401 women with a subsequent pregnancy of known outcome at 10 gestational weeks, 21% received treatment with levothyroxine. 57.7% of subjects had a TPOAb test, which was positive in 9.25% (37/400) in euthyroid, 16.5% (22/133) in borderline-SCH subjects and 35.3% (12/34) in SCH subjects. Treatment did not improve pregnancy continuation rates in borderline-SCH subjects (P = 0.392). There was no difference in pregnancy outcomes based on TPOAb status and treatment for borderline-SCH subjects (P = 0.4214), or based on TPOAb status for euthyroid subjects (P = 0.2668).

CONCLUSIONS

Treatment of hypothyroidism in pregnancy should be initiated based on a TSH >4 mIU/l. Treatment initiation based on thyroid autoimmunity or a TSH >2.5 mIU/l may result in overtreatment.

Effect of antithyroid antibodies on ICSI outcome in antiphospholipid antibody-negative euthyroid women

Antithyroid antibodies (ATA) are found in 5-15% of women at reproductive age and are not necessarily accompanied with thyroid dysfunction. ATA are associated with adverse effects such as spontaneous miscarriage, recurrent miscarriages, preterm delivery and maternal post-partum thyroiditis in women with normal thyroid hormone concentrations. The role of ATA on the outcome of IVF cycles remains to be investigated. This study evaluated the impact of ATA on the outcome of intracytoplasmic sperm injection (ICSI)-embryo transfer cycles in euthyroid women. A total of 253 women undergoing ICSI-embryo transfer cycles were prospectively enrolled in this study. Women positive for at least one of the thyroid antibodies, with normal thyroid-stimulating hormone (TSH) and free T4 concentrations and negative for anticardiolipin antibodies and lupus anticoagulant were included. ICSI was performed for fertilization in all cycles. Of 253 women, 219 were ATA negative and 34 ATA positive. Implantation rates (19.1% versus 18.4%), miscarriage rates (9.0% versus 8.3%) and ongoing pregnancy rates (37.0% versus 32.4%) did not differ significantly between the ATA-positive group and the ATA-negative group, respectively. The presence of antithyroid antibodies in euthyroid and antiphospholipid antibody-negative women was not found to significantly affect the outcome of ICSI-embryo transfer cycles. Antithyroid antibodies (ATA) can interact with thyroid hormone receptors located on the human oocyte and impair the chance of fertilization and healthy pregnancy. They are found in 5-15% of women at reproductive age and are not necessarily accompanied with thyroid dysfunction. ATA have been reported to be associated with adverse effects such as spontaneous miscarriage, recurrent miscarriages, preterm delivery and maternal post-partum thyroiditis in women with normal thyroid hormone concentrations. The role of ATA on the outcome of IVF cycles remains to be investigated. The objective of our study was to evaluate the impact of ATA on the outcome of intracytoplasmic sperm injection (ICSI)-embryo transfer cycles in euthyroid women. A total of 253 women undergoing ICSI-embryo transfer cycles were prospectively enrolled in this study. Women with at least one of the thyroid antibodies positive and normal TSH and free T4 concentrations were included in the study. Since other immunological disorders might affect the results, antiphospholipid antibodies (APA), which are the markers of antiphospholipid antibody syndrome, were also screened in all women prior to study. Women with positive for APA were excluded in the final analysis. Of 253 women, 219 (86.6%) were ATA negative and 34 (13.4%) ATA positive. Implantation rates (19.1% versus 18.4%), biochemical pregnancy rates (9.2% versus 14.3%), miscarriage rates (9.0% versus 8.3%) and ongoing pregnancy rates (37.0% versus 32.4%) did not differ significantly between the ATA-positive group and the ATA-negative group, respectively. In conclusion, presence of antithyroid antibodies in euthyroid and antiphospholipid antibody-negative women does not affect the outcome of ICSI-embryo transfer cycles.

Thyroid peroxidase antibody and screening for postpartum thyroid dysfunction

Postpartum thyroid dysfunction (PPTD) is a common disorder which causes considerable morbidity in affected women. The availability of effective treatment for hypothyroid PPTD, the occurrence of the disease in subsequent pregnancies and the need to identify subjects who develop long term hypothyroidism, has prompted discussion about screening for this disorder. There is currently no consensus about screening as investigations hitherto have been variable in their design, definitions and assay frequency and methodology. There is also a lack of consensus about a suitable screening tool although thyroid peroxidase antibody (TPOAb) is a leading contender. We present data about the use of TPOAb in early pregnancy and its value as a screening tool. Although its positive predictive value is moderate, its sensitivity and specificity when used in early pregnancy are comparable or better compared to other times during pregnancy and the postpartum period. Recent studies have also confirmed this strategy to be cost effective and to compare favourably with other screening strategies. We also explore the advantages of universal screening.

Thyroid function and pregnancy: before, during and beyond

Thyroid disturbances are common in women during the reproductive years of their lives. Autoimmunity and altered iodine status together account for a high proportion of the abnormalities. Autoimmune thyroid disease is present in around 4% of young females, and up to 15% are at risk because they are thyroid antibody-positive. There is a strong relationship between thyroid immunity on the one hand and infertility, miscarriage, and thyroid disturbances in pregnancy and postpartum on the other hand. Suboptimal iodine status affects a large proportion of the world's population, and pregnancy further depletes iodine stores. There is controversy surrounding the degree to which iodine should be supplemented and the duration of supplementation. Recent studies have helped to clarify the relationship between maternal thyroid status and neuropsychological development of the child. The role of other environmental factors including smoking and selenium status is also now recognised. Universal screening for thyroid hormone abnormalities is not routinely recommended at present. However, measurement of thyroid function and autoantibodies should certainly be considered in those who are at high risk of thyroid disease and in those whose pregnancy is otherwise high risk. The practicing clinician needs to be aware of the thyroid changes which accompany pregnancy.

Increased postpartum thyroxine replacement in Hashimoto's thyroiditis

BACKGROUND

The thyroidal response of pregnant patients with established Hashimoto's thyroiditis remains poorly described. The aim of this study was to determine the impact of pregnancy on Hashimoto's thyroiditis as revealed by changes in postpregnancy levothyroxine requirements.

METHODS

We performed a retrospective study of 799 hypothyroid patients in a university hospital. We reviewed the clinical records and selected a group of well-documented pregnant (n = 34) and nonpregnant (n = 32) hypothyroid women for study. We reviewed levothyroxine intake and serum thyrotropin (TSH) levels during three consecutive 9-month time intervals that were immediately before, during, and after pregnancy. We compared the percent change in levothyroxine dose between the prepregnancy level and each trimester during and after pregnancy.

RESULTS

There were two patterns of levothyroxine supplementation during gestation. In pattern 1 (n = 11) there was either no change or a single levothyroxine dose increase with no subsequent changes in each trimester (T1 = T2 = T3). In pattern 2 (n = 18), multistep levothyroxine dose increases were required throughout pregnancy (T1 < T2 < T3) to maintain desired TSH levels (<2.0 mU/L). Women with pattern 2 had mean TSH levels during gestation that differed significantly from pattern 1 (2.8 +/- 0.5 vs. 1.3 +/- 0.1 mU/L respectively; p < 0.03). Further, in multivariate logistic regression, women with pattern 2 were 62 times more likely than women with pattern 1 to have a levothyroxine dose at least 20% above baseline at 3 months postpartum (p = 0.04).

CONCLUSIONS

We showed that >50% of hypothyroid women with Hashimoto's thyroiditis experienced an increase in levothyroxine requirements in the postpartum compared to pregestational doses. This pattern of enhanced levothyroxine need was most likely dependent on the preexisting thyroid functional reserve and postpartum progression of autoimmune destruction.

Thyroid hormones according to gestational age in pregnant Spanish women

BACKGROUND

Thyroid function changes during pregnancy and maternal thyroid dysfunction have been associated with adverse outcomes. Our aim was to evaluate thyroid hormones levels in pregnant women resident in Aragon, Spain.

FINDINGS

Samples for 1198 pregnant women with no apparent thyroid disorders were analyzed, using paramagnetic microparticle and chemiluminescent detection technologies, in order to determine levels of thyroid stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), thyroid peroxidase antibodies (TPO-Ab), and thyroglobulin antibodies (Tg-Ab). Of the women in our sample, 85.22% had normal values for TPO-Ab and Tg-Ab and 14.77% had results revealing the presence of autoimmune diseases of the thyroid. The thyroid hormone reference values obtained according to gestational age (in brackets) were as follows: for free T3, values were 3.38 +/- 0.52 pg/mL (<11 weeks), 3.45 +/- 0.54 pg/mL (11-20 weeks), 3.32 +/- 0.43 pg/mL (21-30 weeks), 3.21 +/- 0.53 pg/mL (31-36 weeks), and 3.23 +/- 0.41 pg/mL (>36 weeks); for free T4, values were 1.10 +/- 0.14 ng/dL (<10 weeks), 1.04 +/- 0.14 ng/dL (11-20 weeks), 0.93 +/- 0.12 ng/dL (21-30 weeks), 0.90 +/- 0.13 ng/dL (31-36 weeks), and 0.80 +/- 0.21 ng/dL (>36 weeks); and for TSH, values were (muIU/mL): 1.12 +/- 0.69 (<10 weeks), 1.05 +/- 0.67 (11-20 weeks), 1.19 +/- 0.60 (21-30 weeks), 1.38 +/- 0.76 (31-36 weeks), and 1.46 +/- 0.72 (>36 weeks).

CONCLUSION

Pregnant women with normal antibody values according to gestational age had values for FT4 and TSH, but not for FT3, that differed to a statistically significant degree. The values we describe can be used as reference values for the Aragon region of Spain.

The diagnostic role of autoantibodies in the prediction of organ-specific autoimmune diseases

Due to their pathogenetic role, many serum autoantibodies can be detected a long time before the clinical onset and during the course of organ-specific autoimmune diseases. For these reasons, autoantibodies can be used as predictive markers of an ongoing disease (in healthy subjects) and of disease activity and severity (in ill patients). The new multiplex diagnostic technologies introduced recently in laboratory medicine allow the simultaneous detection of several different autoantibodies and can be used for screening purposes in open populations or high-risk groups. This review examines the various autoantibodies of demonstrated predictive role in organ-specific autoimmune diseases and it introduces the state-of-the-art in the detection of multiple autoantibodies with proteomic systems.