Introduction: Hyperthyroidism in pregnancy is a serious condition and its management is complex. Whilst carbimazole/methimazole (CBZ/MMI) and propylthiouracil (PTU) have similar efficacies in controlling hyperthyroidism, their risk of side effects such as major congenital abnormalities and hepatotoxicity are different. Methods: Various combinations of the terms ‘anti-thyroid drugs’, ‘thionamide’, ‘carbimazole’, ‘methimazole’, ‘propylthiouracil’, ‘pregnancy’, ‘side effects’, ‘agranulocytosis’, ‘birth defects’, ‘congenital malformations’, ‘embryopathy’, ‘aplasia cutis’, ‘hepatotoxicity’, ‘hepatic failure’, ‘maternal’ and ‘fetus’ were used to search MEDLINE and the Cochrane library. The references of retrieved papers were also reviewed. Results: There is increasing evidence for a CBZ/MMI embryopathy, whilst data remain lacking for major congenital abnormalities with PTU. In contrast, PTU is associated with increased risk of severe liver injury. Management strategies to reduce these risks by using PTU in the first trimester and CBZ/MMI in the later trimesters remain untested. Conclusion: More evidence is still needed in defining the relative risks between CBZ/MMI and PTU of major congenital abnormalities and severe liver injury in pregnancy. Studies are also needed to establish the suitability of recent management suggestions in switching from PTU to CBZ/MMI after the first trimester. Major adverse outcomes secondary to CBZ/MMI and PTU are rare, and inadequately treated hyperthyroidism poses a far greater risk.

Background: An optimal management of maternal hyperthyroidism is important for positive pregnancy outcome, and to this end, the Endocrine Society published their guidelines in 2007. This survey aimed to investigate to what extent the clinical practice relating to the management of hyperthyroidism during pregnancy in Europe is uniform and consistent with the guidelines. Materials and Methods: We e-mailed an online questionnaire survey based on clinical case scenarios to 605 members of the European Thyroid Association. We analysed 190 responses from 28 European countries. Results: For a woman with newly diagnosed Graves’ disease (GD) and wishing pregnancy, 78% of the responders would initiate antithyroid drugs (ATDs), while 22% would recommend definitive treatment with radioiodine or surgery. In case of a relapsed GD before pregnancy, 80% preferred definitive treatment. For a woman with newly diagnosed GD during pregnancy, 53% would treat with propylthiouracil, 12% with methimazole, and 34% with propylthiouracil initially and switch to methimazole after the first trimester. Responders used several combinations of tests to monitor the dose of ATDs, and the thyroid test results they targeted were inconsistent. For a lactating woman with GD, 68% would give ATDs without stopping lactation. Conclusions: Variation in the clinical practices surrounding the management of hyperthyroid pregnant women in Europe still exists.

This guideline has been produced as the official statement of the European Thyroid Association guideline committee. Subclinical hypothyroidism (SCH) in pregnancy is defined as a thyroid-stimulating hormone (TSH) level above the pregnancy-related reference range with a normal serum thyroxine concentration. Isolated hypothyroxinaemia (defined as a thyroxine level below the 2.5th centile of the pregnancy-related reference range with a normal TSH level) is also recognized in pregnancy. In the majority of SCH the cause is autoimmune thyroiditis but may also be due to iodine deficiency. The cause of isolated hypothyroxinaemia is usually not apparent, but iodine deficiency may be a factor. SCH and isolated hypothyroxinaemia are both associated with adverse obstetric outcomes. Levothyroxine therapy may ameliorate some of these with SCH but not in isolated hypothyroxinaemia. SCH and isolated hypothyroxinaemia are both associated with neuro-intellectual impairment of the child, but there is no evidence that maternal levothyroxine therapy improves this outcome. Targeted antenatal screening for thyroid function will miss a substantial percentage of women with thyroid dysfunction. In children SCH (serum TSH concentration >5.5-10 mU/l) normalizes in >70% and persists in the majority of the remaining patients over the subsequent 5 years, but rarely worsens. There is a lack of studies examining the impact of SCH on the neuropsychological development of children under the age of 3 years. In older children, the evidence for an association between SCH and impaired neuropsychological development is inconsistent. Good quality studies examining the effect of treatment of SCH in children are lacking.