Neonatal Graves' Disease with Maternal Hypothyroidism

Neonatal Thyrotoxicosis in Infants of Mothers with Graves' Disease Treated for Radioiodine-Induced Hypothyroidism: A Literature Review

Fetal and neonatal thyrotoxicosis occurs in up to 5% of pregnancies in mothers with Graves' disease (GD). This condition is caused by stimulating antibodies against the thyrotropin receptor (TRAbs) that cross the placenta and may stimulate the fetal thyroid, typically in the second half of pregnancy. GD is often treated with radioiodine, resulting in hypothyroidism in most patients, but TRAbs can persist for several years. Even if a pregnant mother is hypothyroid after radioiodine therapy or surgery, her TRAbs can still, although rarely, induce fetal hyperthyroidism. In this review, we first present two cases of neonatal hyperthyroidism in mothers with GD who became hypothyroid after prior radioiodine therapy, identified through a 10-year analysis of the National Perinatal System in Slovenia. Based on these cases, we provide an overview of existing data on this rare clinical condition in neonates. We also discuss the underlying mechanisms and clinical outcomes based on currently available data. In conclusion, our review highlights the importance of careful monitoring during pregnancy in all women with GD, even in those well managed after radioiodine therapy or surgery.

Neonatal thyrotoxicosis with maternal hypothyroidism

Neonatal Graves' is uncommon, but a potentially fatal condition caused by transplacental transfer of thyroid stimulating immunoglobulin (TSI). It is seen in 1%-5% of infants born to a mother with Graves' disease. Here, we report a unique case of transient neonatal thyrotoxicosis with positive TSI in a premature neonate born to the mother with primary hypothyroidism. A short course of antithyroid drug treatment leads to significant clinical and biochemical improvement followed by complete recovery.

Combined use of thyroid stimulating hormone plus free thyroxine levels and gestational age at birth for the prediction of neonatal hypothyroidism and associated risk factors

The present study aimed to explore the effectiveness of the combined use of thyroid-stimulating hormone (TSH) and free thyroxine [(FT4); TSH+FT4] levels and gestational age at birth to predict neonatal hypothyroidism and to identify the risk factors associated with the disease. The clinical data of 686 neonates with suspected hypothyroidism (TSH >10 mIU/l) who were admitted to The First Affiliated Hospital of Chongqing Medical University were retrospectively analyzed. From these, 70 neonates with confirmed hypothyroidism were assigned to the patient group and another 70 neonates with normal thyroid function to the normal (control) group. Sex, gestational age at birth, Apgar score, birth weight, body length, head circumference and heart rate data were collected. TSH and FT4 levels were measured by electrochemiluminescence immunoassay, and the predictive value of combined use of TSH+FT4 and gestational age at birth on neonatal hypothyroidism was analyzed. The prespecified secondary outcomes were the risk factors for neonatal hypothyroidism determined using univariate and logistic regression analyses. TSH levels were significantly higher, whereas FT4 levels were lower in the patient group at 3 days of age compared with the control group (P<0.05). After 8-week treatment with thyroxine, these levels were not significantly different between the patient and control groups (P<0.05). The combined use of TSH+FT4 levels and gestational age at birth to predict neonatal hypothyroidism demonstrated a significantly improved sensitivity, specificity, accuracy, positive predictive value and negative predictive value (92.86, 97.26, 96.76, 81.25 and 99.07%, respectively) compared with the use of only TSH+FT4 levels (P<0.05). Logistic regression analysis revealed a low gestational age at birth, maternal thyroid dysfunction and low birth weight were risk factors for neonatal hypothyroidism (P<0.05). The combined use of TSH+FT4 levels and gestational age at birth resulted in an improved prediction of neonatal hypothyroidism and contributed to early therapeutic intervention. Thus, special intervention is necessary for pregnant women with thyroid dysfunction to reduce the incidence of neonatal hypothyroidism.

Graves' hyperthyroidism in pregnancy

PURPOSE OF REVIEW

Graves' hyperthyroidism is associated with significant obstetric, maternal, fetal, and neonatal complications. Early diagnosis and an understanding of the management of Graves' hyperthyroidism in pregnancy can help to prevent these complications. Antithyroid drugs (ATD) should be avoided in early pregnancy, given their association with congenital malformations.

RECENT FINDINGS

TSH-receptor antibodies (TRAb) are integral in the management of Graves' hyperthyroidism in pregnancy and in the preconception period. TRAb are indicative of the current activity of Graves' hyperthyroidism and the likelihood of relapse. Furthermore, TRAb predicts the risk of fetal and neonatal hyperthyroidism.The incidence of congenital malformations is roughly the same for propylthiouracil (PTU) and methimazole (MMZ). Exposure to both ATDs in early pregnancy has been associated with increased incidence of congenital malformations compared with exposure to either ATD alone.

SUMMARY

The goal of the physician is maintaining euthyroidism throughout pregnancy and delivery of a healthy, euthyroid baby. An understanding of the natural progression of Graves' hyperthyroidism in pregnancy and the proper utilization of TRAb enables the physician to minimize the risks associated with Graves' hyperthyroidism and side effects of ATDs unique to pregnancy. The physician should prioritize preconception counseling in women with Graves' hyperthyroidism in order to avoid hyperthyroidism and having to use ATDs in pregnancy.

Thyroglobulin Is Markedly Elevated in 6- to 24-Month-Old Infants at Both Low and High Iodine Intakes and Suggests a Narrow Optimal Iodine Intake Range

BACKGROUND

In areas with incomplete salt iodization coverage, infants and children aged 6-24 months weaning from breast milk and receiving complementary foods are at risk of iodine deficiency. However, few data exist on the risk of excessive iodine intake in this age group. Thyroglobulin (Tg) is a sensitive marker of iodine intake in school-age children and adults and may be used to estimate the optimal iodine intake range in infancy. The aim of this study was to assess the association of low and high iodine intakes with Tg and thyroid function in weaning infants.

METHODS

This multicenter cross-sectional study recruited infants aged 6-24 months (n = 1543; M_age = 12.2 ± 4.6 months) receiving breast milk with complementary foods, from seven countries in areas with previously documented deficient, sufficient, or excessive iodine intake in schoolchildren or pregnant women. Urinary iodine concentration (UIC) and Tg, total thyroxine, and thyrotropin were measured using dried blood spot testing.

RESULTS

Median UIC ranged from 48 μg/L (interquartile range 31-79 μg/L) to 552 μg/L (interquartile range 272-987 μg/L) across the study sites. Median Tg using dried blood spot testing was high (>50 μg/L) at estimated habitual iodine intakes <50 μg/day and >230 μg/day. Prevalence of overt thyroid disorders was low (<3%). Yet, subclinical hyperthyroidism was observed in the countries with the lowest iodine intake.

CONCLUSIONS

Tg is a sensitive biomarker of iodine intake in 6- to 24-month-old infants and follows a U-shaped relationship with iodine intake, suggesting a relatively narrow optimal intake range. Infants with low iodine intake may be at increased risk of subclinical thyroid dysfunction. In population monitoring of iodine deficiency or excess, assessment of iodine status using UIC and Tg may be valuable in this young age group.