Risk factors for neonatal thyroid dysfunction in pregnancies complicated by Graves’ disease

Clinical features of neonatal hyperthyroidism: a retrospective analysis in southwestern China

Purpose

This study aimed to explore the clinical characteristics and evaluate the different types of thyroid dysfunction in babies with neonatal hyperthyroidism.

Methods

The clinical data of 19 neonates with hyperthyroidism admitted to the Children's Hospital of Chongqing Medical University between January 2012 and April 2021 were retrospectively analyzed.

Results

Fifteen (78.9%) infants were born to mothers with Graves' disease. Eleven (57.9%) infants were premature; two babies were born at small for gestational age. The age at diagnosis ranged from 3 to 34 days, with a mean of 18.53 ± 6.85 days. The majority of the babies presented with goiter (84.2%) and tachycardia (94.7%) after birth. Nine (47.4%) of them presented with abnormal weight gain, seven (36.8%) presented with stare or ocular protrusion, six (31.6%) presented with hyperexcitability, four (21.1%) presented with jaundice and liver dysfunction, two (10.5%) presented with sweating, one (5.3%) presented with fever, and one case presented without any symptoms. Transient hyperthyroidism was the main thyroid dysfunction in our study. Overt hyperthyroidism was diagnosed in 13 (68.4%) neonates. Another three babies (15.8%) presented with hyperthyroidism with slightly elevated free triiodothyronine levels, normal thyroxine (T4) levels, and low thyroid-stimulating hormone (TSH) levels. Normal thyroid hormone levels with low TSH levels were observed in three (15.8%) neonates. Ten children were treated with antithyroid drugs. Eighteen children recovered normal thyroid function at 1-3 months of age; one baby in the study group required further levothyroxine supplementation due to primary hypothyroidism (HT). One child was found to have developmental delay at 2 years of age during follow-up.

Conclusions

Our study highlights the need for prolonged monitoring of thyroid function in suspected patients. A single normal screening for hyperthyroidism or the absence of a maternal history of hyperthyroidism cannot exclude this disease.

Third-Generation Thyrotropin Receptor Antibody (TRAb) assay for predicting neonatal thyroid dysfunction in pregnant women with Graves' disease

PURPOSE

The aim is to validate the third generation Thyrotropin receptor antibody (TRAb) assay for predicting neonatal thyroid dysfunction and adverse pregnancy outcomes in pregnant women with Graves' disease.

METHODS

This prospective cohort study was conducted in TRAb positive pregnant women with Graves' disease and their off springs. The primary outcome was to assess different forms of neonatal thyroid dysfunction in relation to maternal and neonatal TRAb levels. The secondary outcome was to predict adverse pregnancy outcomes by using maternal TRAb levels. Serum T3, FT4, TSH, TRAb levels were measured using electrochemiluminescence immunoassay.

RESULTS

51 pregnant women were included. Five women had adverse pregnancy outcomes, TRAb levels of > 19.06 IU/L (10.9 times the upper limit of normal (ULN)) predicted adverse pregnancy outcomes with 100% sensitivity and 93.5% specificity. Among the 46 successful live births, 13 (28.3%) had neonatal thyroid dysfunction. Out of 13 neonates, 7 (32%) had neonatal thyrotoxicosis, 4 (18%) had primary hypothyroidism, and 2 (9%) had central hypothyroidism. Third trimester maternal TRAb levels of > 7.99 IU/L (4.6 times the ULN)and day three neonatal TRAb levels of > 5.03 IU/L (2.9 times the ULN), predicted the neonatal thyrotoxicosis with 100% sensitivity and 97.4% specificity.

CONCLUSION

Very high maternal third generation TRAb levels strongly predicted the adverse pregnancy outcomes and neonatal thyroid dysfunction in pregnant women with Graves' disease. Neonatal thyroid function test along with the TRAb levels strongly correlated with different forms of neonatal thyroid dysfunction and is very useful in avoiding inadvertent treatment to neonates.

A unique presentation of Graves' disease in a pregnant woman with severe hypothyroidism

BackgroundGraves' disease occurrence during pregnancy is not a frequent event, showing an incidence of 0.2-0.4% in unselected pregnant women. Depending on their functional properties, TSH-receptor antibodies can induce hypothyroidism or hyperthyroidism. Recognizing the signs of altered thyroid function is essential to prevent possible complications on the fetus.Materials and methodsThe case of a pregnant woman without previous history of thyroid disease presenting with severe overt hypothyroidism during the first trimester is reported. Levothyroxine therapy was started and 6 weeks later overt hyperthyroidism was observed. TRAb were detected at high titers. Levothyroxine was withdrawn and low dose methimazole was started. Serial obstetric ultrasound scans were negative for indirect signs of fetal thyroid dysfunctions and no fetal goiter was visualized throughout pregnancy. Spontaneous delivery occurred without complications at 39 weeks of gestation. In the post-partum, severe overt hypothyroidism recurred, thus methimazole was discontinued and levothyroxine was restarted. TRAb persisted at high levels. The infant experienced a transient thyrotoxicosis, which fully resolved in three months with normalization of thyroid function and negativization of TRAb levels.ResultsThe present case report allows us to overview the challenges related to the management of hypo and hyperthyroidism in patients with high TRAb levels, requiring strict monitoring aimed at early detection of both maternal and fetal consequences.ConclusionsThis case underlines the importance of close follow-up and the need of collaboration in a multidisciplinary team when Graves's disease is diagnosed in a pregnant woman to prevent adverse neonatal outcomes.

Follow-Up of Thyroid Function in Children With Neonatal Hyperthyroidism

INTRODUCTION

Neonatal hyperthyroidism mainly occurring in the children born to mothers with Graves' disease (GD). The influence of maternal GD on the newborn's thyroid function includes not only hyperthyroidism, but also various forms of hypothyroidism. Maternally transferred thyrotropin receptor antibodies (TRAb), the antithyroid drug (ATD) administration during pregnancy and previous definitive treatment of GD (radioactive iodine therapy or thyroidectomy) in the mother impact the function of the fetal/neonatal thyroid. Some newborns born to mothers with GD may present central hypothyroidism (CeH) due to impaired regulation of the fetal hypothalamic-pituitary-thyroid axis. The aim of this study was to evaluate different types of thyroid dysfunction in babies with neonatal hyperthyroidism.

MATERIALS AND METHODS

Medical records of 14 infants with neonatal hyperthyroidism (13 born to mothers with GD, and one born to mother with Hashimoto thyroiditis) were analyzed.

RESULTS

Transient hyperthyroidism was the main thyroid dysfunction in our study group. Overt hyperthyroidism with highly increased TRAb levels (mean 13.0 ± 7.0 IU/L) was diagnosed in 6 (43%) neonates. Another 6 (43%) babies presented hyperthyroidism with slightly increased fT4 and/or fT3 levels and TSH levels in the lower limit of the normal range coinciding with positive TRAb levels (mean 3.8 ± 1.6 IU/L). Normal thyroid hormone levels with TSH levels below the lower limit of the range were observed in 2 (14%) neonates. Four babies in the study group (28.5%) required further levothyroxine (L-T4) supplementation due to CeH or, in one case, due to primary hypothyroidism.

CONCLUSION

Our study highlights the need for prolonged monitoring of thyroid function in children born to mothers with GD. Diagnosis of CeH could be delayed due to its masking by transient hyperthyroidism. Prolonged thyroid-stimulating hormone suppression after TRAb elimination should be considered as a signal announcing CeH.

Congenital Hypothyroidism in Preterm Newborns - The Challenges of Diagnostics and Treatment: A Review

Preterm newborns are forced to adapt to harsh extrauterine conditions and endure numerous adversities despite their incomplete growth and maturity. The inadequate thyroid hormones secretion as well as the impaired regulation of hypothalamus-pituitary-thyroid axis may lead to hypothyroxinemia. Two first weeks after birth are pivotal for brain neurons development, synaptogenesis and gliogenesis. The decreased level of thyroxine regardless of cause may lead to delayed mental development. Congenital hypothyroidism (CH) is a disorder highly prevalent in premature neonates and it originates from maternal factors, perinatal and labor complications, genetic abnormalities, thyroid malformations as well as side effects of medications and therapeutic actions. Because of that, the prevention is not fully attainable. CH manifests clinically in a few distinctive forms: primary, permanent or transient, and secondary. Their etiologies and implications bear little resemblance. Therefore, the exact diagnosis and differentiation between the subtypes of CH are crucial in order to plan an effective treatment. Hypothyroxinemia of prematurity indicates dynamic changes in thyroid hormone levels dependent on neonatal postmenstrual age, which directly affects patient's maintenance and wellbeing. The basis of a successful treatment relies on an early and accurate diagnosis. Neonatal screening is a recommended method of detecting CH in preterm newborns. The preferred approach involves testing serum TSH and fT4 concentrations and assessing their levels according to the cut-off values. The possible benefits also include the evaluation of CH subtype. Nevertheless, the reference range of thyroid hormones varies all around the world and impedes the introduction of universal testing recommendations. Unification of the methodology in neonatal screening would be advantageous for prevention and management of CH. Current guidelines recommend levothyroxine treatment of CH in preterm infants only when the diagnose is confirmed. Moreover, they underline the importance of the re-evaluation among preterm born infants due to the frequency of transient forms of hypothyroidism. However, results from multiple clinical trials are mixed and depend on the newborn's gestational age at birth. Some benefits of treatment are seen especially in the preterm infants born <29 weeks' gestation. The discrepancies among trials and guidelines create an urgent need to conduct more large sample size studies that could provide further analyses and consensus. This review summarizes the current state of knowledge on congenital hypothyroidism in preterm infants. We discuss screening and treatment options and demonstrate present challenges and controversies.

Dose-Dependent Influence of Antithyroid Drugs on the Difference in Free Thyroxine Levels between Mothers with Graves' Hyperthyroidism and Their Neonates

BACKGROUND

Several guidelines have recommended that the use of the lowest effective dose of antithyroid drugs (ATDs) that maintains maternal serum free thyroxine (FT4) levels at or moderately above the upper limit of the reference range is appropriate for fetal euthyroid status. However, little is known about whether ATD dosage affects the difference in serum FT4 levels between the mother and neonate. We conducted a retrospective study at a tertiary hospital in Japan to investigate the dose-dependent influence of ATDs on both maternal and fetal thyroid hormone status.

MATERIALS AND METHODS

We retrospectively examined 62 pregnant women who delivered between 2007 and 2016 and were treated for Graves' hyperthyroidism with ATD at any stage during pregnancy. We selected individuals whose data on maternal FT4 level within 4 weeks of their deliveries and cord FT4 level of their infants at the time of delivery were available. Those with multiple pregnancies, iodine or glucocorticoid treatment, and fetal goiter detected by ultrasonography were excluded.

RESULTS

After the exclusion criteria were applied, we recruited 40 individuals. The cord FT4 levels were significantly lower than the maternal FT4 levels in patients treated with high-dosage ATDs (methimazole >5 mg daily or propylthiouracil >100 mg daily). However, there were no significant differences between maternal and cord FT4 levels in patients treated with low-dosage ATDs (methimazole ≤5 mg daily or propylthiouracil ≤100 mg daily). We selected 35 individuals whose data on maternal thyrotropin receptor-binding inhibitory immunoglobulin (TBII) level were available. Multiple linear regression analysis adjusted for ATD dosage, maternal TBII level, and gestational period found that ATD dosage was a significant predictor of the difference in serum FT4 levels between the mother and neonate. In terms of maternal complications, multiple logistic regression analysis identified maternal free triiodothyronine (FT3) level as a significant predictor of the incidence of preterm delivery.

CONCLUSIONS

We found a dose-dependent influence of ATDs on the difference in serum FT4 levels between mothers with Graves' hyperthyroidism and their neonates. Further studies to evaluate the optimal target FT4 and FT3 levels for the mother and neonate during pregnancy may improve the outcome of pregnant women with Graves' hyperthyroidism.

Thyroid Disease in Pregnancy: ACOG Practice Bulletin, Number 223

Both thyrotoxicosis and hypothyroidism are associated with adverse pregnancy outcomes. There also is concern about the effect of overt maternal thyroid disease on fetal development. In addition, medications that affect the maternal thyroid gland can cross the placenta and affect the fetal thyroid gland. This document reviews the thyroid-related pathophysiologic changes that occur during pregnancy and the effects of overt and subclinical maternal thyroid disease on maternal and fetal outcomes. This Practice Bulletin has been updated with information on the diagnosis and the management of thyroid disease in pregnant women and includes a new clinical algorithm on management of thyroid disease in pregnancy.

Incidence of Neonatal Hyperthyroidism Among Newborns of Graves' Disease Patients Treated with Radioiodine Therapy

BACKGROUND

The serum thyrotropin receptor antibody (TRAb) titers of Graves' disease (GD) patients are known to increase after radioiodine (RAI) therapy, and they can remain high for years. The incidence of neonatal hyperthyroidism (NH) among newborns of mothers with GD who conceived after RAI therapy has not been previously reported. The aims of this study were to investigate the incidence of NH among newborns of mothers who conceived within two years after RAI therapy, and to identify predictors of NH.

METHODS

GD patients (n = 145) who conceived within two years after RAI therapy were retrospectively reviewed, and information regarding their newborns was collected.

RESULTS

Of the 145 pregnant women, 54 (37%) were treated with antithyroid drugs or potassium iodide for maternal hyperthyroidism during the first trimester. There were eight newborns with NH, resulting in an incidence of 5.5%. Seven of the eight mothers whose newborns had NH were treated with antithyroid drugs or potassium iodide during their pregnancy. The incidence of NH among the newborns of mothers who conceived within 6-12 months after RAI therapy was 8.8%, within 12-18 months was 5.5%, and within 18-24 months was 3.6%. Multivariate analysis revealed that the TRAb values in the third trimester were the only risk factor for NH. The cutoff TRAb value in the third trimester for predicting NH was 9.7 IU/L (reference value <2.0 IU/L).

CONCLUSIONS

The incidence of NH among newborns of mothers who conceived within two years after RAI therapy was 5.5%. The fetuses of pregnant GD patients whose TRAb value is high in the third trimester should be carefully followed by an obstetrician during pregnancy, and the newborns should be carefully followed by a pediatrician after birth.

Central congenital hypothyroidism caused by maternal thyrotoxicosis

Central congenital hypothyroidism (CCH) is a rare and underdiagnosed disease that sometimes is caused by maternal Graves' disease. We report a case of CCH caused by undiagnosed, initially antibody-negative maternal thyrotoxicosis with possible disruption of fetal hypothalamic-pituitary-thyroid axis maturation. In CCH, maternal thyroid disease should be considered.

Maternal Thyrotropin Receptor Antibody Concentration and the Risk of Fetal and Neonatal Thyrotoxicosis: A Systematic Review

BACKGROUND

In pregnant women with Graves' disease, maternal thyrotropin receptor antibodies (TRAb) can cross the placenta and induce fetal or neonatal thyrotoxicosis. Symptoms of fetal thyrotoxicosis are tachycardia, intrauterine growth restriction, and intra-uterine death. Recommendations on an upper limit of TRAb concentrations below which intensive fetal monitoring can be safely omitted vary between different guidelines. The objective of this study was to define an evidence-based cutoff level for maternal TRAb necessitating additional fetal monitoring during pregnancy.

METHODS

A literature search was performed to identify studies on pregnant women with Graves' disease and fetal and/or neonatal thyrotoxicosis. Only studies that reported TRAb were included.

RESULTS

From a total of 229 identified titles, 20 articles could be included in the analysis. A total of 53 cases of fetal and/or neonatal thyrotoxicosis were described. The lowest level of maternal TRAb leading to neonatal thyrotoxicosis was 4.4 U/L, which corresponds to 3.7 times the upper limit of normal. The level of evidence for this threshold is moderate to low.

CONCLUSION

In women with Graves' disease, intensive fetal monitoring is recommended when maternal TRAb concentrations are >3.7 times the upper limit of normal. This cutoff level should be interpreted with caution, since evidence is limited.

Thyroid-Stimulating Hormone Receptor Antibodies in Pregnancy: Clinical Relevance

Graves' disease is the most common cause of thyrotoxicosis in women of childbearing age. Approximately 1% of pregnant women been treated before, or are being treated during pregnancy for Graves' hyperthyroidism. In pregnancy, as in not pregnant state, thyroid-stimulating hormone (TSH) receptor (TSHR) antibodies (TRAbs) are the pathogenetic hallmark of Graves' disease. TRAbs are heterogeneous for molecular and functional properties and are subdivided into activating (TSAbs), blocking (TBAbs), or neutral (N-TRAbs) depending on their effect on TSHR. The typical clinical features of Graves' disease (goiter, hyperthyroidism, ophthalmopathy, dermopathy) occur when TSAbs predominate. Graves' disease shows some peculiarities in pregnancy. The TRAbs disturb the maternal as well as the fetal thyroid function given their ability to cross the placental barrier. The pregnancy-related immunosuppression reduces the levels of TRAbs in most cases although they persist in women with active disease as well as in women who received definitive therapy (radioiodine or surgery) before pregnancy. Changes of functional properties from stimulating to blocking the TSHR could occur during gestation. Drug therapy is the treatment of choice for hyperthyroidism during gestation. Antithyroid drugs also cross the placenta and therefore decrease both the maternal and the fetal thyroid hormone production. The management of Graves' disease in pregnancy should be aimed at maintaining euthyroidism in the mother as well as in the fetus. Maternal and fetal thyroid dysfunction (hyperthyroidism as well as hypothyroidism) are in fact associated with several morbidities. Monitoring of the maternal thyroid function, TRAbs measurement, and fetal surveillance are the mainstay for the management of Graves' disease in pregnancy. This review summarizes the biochemical, immunological, and therapeutic aspects of Graves' disease in pregnancy focusing on the role of the TRAbs in maternal and fetal function.

Management of Neonates Born to Mothers With Graves' Disease

Neonates born to mothers with Graves' disease are at risk for significant morbidity and mortality and need to be appropriately identified and managed. Because no consensus guidelines regarding the treatment of these newborns exist, we sought to generate a literature-based management algorithm. The suggestions include the following: (1) Base initial risk assessment on maternal thyroid stimulating hormone (TSH) receptor antibodies. If levels are negative, no specific neonatal follow-up is necessary; if unavailable or positive, regard the newborn as "at risk" for the development of hyperthyroidism. (2) Determine levels of TSH-receptor antibodies in cord blood, or as soon as possible thereafter, so that newborns with negative antibodies can be discharged from follow-up. (3) Measurement of cord TSH and fT4 levels is not indicated. (4) Perform fT4 and TSH levels at day 3 to 5 of life, repeat at day 10 to 14 of life and follow clinically until 2 to 3 months of life. (5) Use the same testing schedule in neonates born to mothers with treated or untreated Graves' disease. (6) When warranted, use methimazole (MMI) as the treatment of choice; β-blockers can be added for sympathetic hyperactivity. In refractory cases, potassium iodide may be used in conjunction with MMI. The need for treatment of asymptomatic infants with biochemical hyperthyroidism is uncertain. (7) Assess the MMI-treated newborn on a weekly basis until stable, then every 1 to 2 weeks, with a decrease of MMI (and other medications) as tolerated. MMI treatment duration is most commonly 1 to 2 months. (8) Be cognizant that central or primary hypothyroidism can occur in these newborns.