Hyperthyroidism in Pregnancy: The Delicate Balance between Too Much or Too Little Antithyroid Drug

Abstract

Overt hyperthyroidism (HT) during pregnancy is associated with a risk of maternal–fetal complications. Antithyroid drugs (ATD) have a potential risk for teratogenic effects and fetal–neonatal hypothyroidism. This study evaluated ATD treatment and thyroid function control during pregnancy, and pregnancy outcome in women with HT. Patients and methods: A retrospective analysis of 36 single fetus pregnancies in 29 consecutive women (median age 30.3 ± 4.7 years) with HT diagnosed before or during pregnancy; a control group of 39 healthy euthyroid pregnant women was used. Results: Twenty-six women had Graves’ disease (GD, 33 pregnancies), 1 had a hyperfunctioning autonomous nodule, and 2 had gestational transient thyrotoxicosis (GTT). Methimazole (MMI) was administered in 22 pregnancies (78.5%), Propylthiouracil (PTU) in 2 (7.1%), switch from MMI to PTU in 4 (14.2%), no treatment in 8 pregnancies (3 with subclinical HT, 5 euthyroid with previous GD remission before conception). In the 8 pregnancies of GD patients diagnosed during gestation or shortly before (<6 weeks), i.e., with fetal exposure to uncontrolled HT, there was 1 spontaneous abortion at 5 weeks (3.4% of all ATD-treated pregnancies), and 1 premature delivery at 32 weeks with neonatal death in 24 h (3.4%); 1 child had neonatal hyperthyroidism (3.3% of live children in GD women) and a small atrial sept defect (4% of live children in ATD treated women). In women treated more than 6 months until conception (20 pregnancies): (a) median ATD doses were lower than those in women diagnosed shortly before or during pregnancy; (b) ATD was withdrawn in 40% of pregnancies in trimester (T)1, all on MMI < 10 mg/day (relapse in 14.2%), and in up to 55% in T3; (c) TSH level was below normal in 37%, 35% and 22% of pregnancies in T1, T2 and T3 respectively; FT4 was increased in 5.8% (T1) and subnormal in 11.75% in T2 and T3; (d) no fetal birth defects were recorded; one fetal death due to a true umbilical cord knot was registered. Mean birth weight was similar in both ATD-treated and control groups. Hyperthyroidism relapsed postpartum in 83% of GD patients (at median 3 ± 2.6 months). Conclusion: In hyperthyroid women with long-term ATD treatment before conception, drugs could be withdrawn in T1 in 40% of them, the thyroid function control was better, and pregnancy and fetal complications were rarer, compared to women diagnosed during pregnancy. Frequent serum TSH and FT4 monitoring is needed to maintain optimal thyroid function during pregnancy.

Characteristics of Pregnant Women with Thyroid Disorders at Wahidin Sudirohusodo Hospital Makassar

“…In this study, from pregnancy history, we found that 60 % of pregnant women were multipara, 26.7 % were primipara dan 13.3 % were Grande para. Among those women, 56.7 % had a history of cesarean section for previous labor methods, Diagnosis and complaints of thyroid disorders in pregnant women in this study were found in the second and third trimesters, similar to research conducted by Gheorghiu et al, 2021. In most cases, thyroid disorders in pregnancy, such as subclinical hyperthyroidism, appear after the sixth week of pregnancy due to increased physiological secretions (11).…”

The Impact of Hyperthyroidism on Fertility, Maternal, Foetal and Perinatal Outcomes in the Era of Iodine Fortification

“…Pregnancy among women with hyperthyroidism faces a two-pronged challenge: potential complications from metabolic derangements secondary to excessive thyroid hormones and circulating auto-antibodies among women with Graves' disease; and the adverse effects of the varied treatment remedies aimed at the control thyroid function close to the normal state [4]. The principles of preconception care for women with hyperthyroidism are to use effective contraception until the patient achieves a sustained euthyroid state [42]. This will reduce the complications associated with the deranged metabolic state due to excessive thyroid hormones in the circulation.…”

Can Thyroid Screening in the First Trimester Improve the Prediction of Gestational Diabetes Mellitus?

“…The frequency of antithyroid antibodies, thyroid peroxidase antibody-anti TPO Ab or thyroglobulin antibody-anti Tg Ab in euthyroid pregnant women, according to different authors, is about 10% (2-18%) [17][18][19], while the antibodies can be found in 30-60% of hypothyroid pregnant women [16]. Thyroid disorder in pregnancy is associated with an increased risk of adverse pregnancy outcomes and pregnancy complications [11,20,21]. Subclinical hypothyroidism, if not treated, may increase the risk of miscarriage, early intrauterine fetal death [10,22], pregnancy anemia, hypertension, preeclampsia [23], postpartum hemorrhage, placental abruption [11,24] and gestational diabetes mellitus [25].…”