Graves Hyperthyroidism and Pregnancy: A Clinical Update

Komal Patil-Sisodia, MD; Jorge H. Mestman, MD

Disclosures

Endocr Pract. 2010;16(1):118-129. 

In This Article

Conclusion

The endocrinologist has a very important role in prepregnancy counseling of women with active Graves hyperthyroidism or women with a history of this disease who wish to conceive. The possibility of disease recurrence during pregnancy or in the postpartum period and the risk of fetal thyroid dysfunction in women with persistently high levels of TRAb should be carefully discussed with the patient and her partner. The diagnosis of hyperthyroidism during the first half of gestation poses a challenge for most physicians. Gestational thyrotoxicosis is the most common form of hyperthyroidism during pregnancy and resolves spontaneously by 14 to 20 weeks' gestation. Graves hyperthyroidism is the next most common cause of hyperthyroidism, and it may be difficult to distinguish from gestational thyrotoxicosis in early pregnancy, although symptoms often antedate pregnancy. A thorough medical history and physical examination usually help distinguish between the 2 conditions.

Antithyroid drugs remain the mainstay of treatment and are very effective in controlling the symptoms of thyrotoxicosis. The use of PTU during the first trimester, followed by a change to methimazole during the second and third trimesters is advocated because of the high incidence of fulminant hepatic failure with the use of PTU in adults and children. Methimazole is not recommended in the first trimester because of the rare possibility of congenital lesions, the so-called methimazole embryopathy. β-Adrenergic blockers can also be added to help control severe symptoms. The goal of antithyroid drug therapy is to achieve free T4 index values in the upper third of normal, and adjustment of the antithyroid drug dosage is advocated every 2 to 4 weeks. Because of immunomodulation during pregnancy, up to one-third of patients may be able to stop antithyroid drug therapy in the last 4 to 8 weeks of pregnancy. If hyperthyroidism is not controlled by antithyroid drugs and β-adrenergic blockers, surgery may be indicated during the second trimester.

The rates of maternal and perinatal complications are directly related to control of hyperthyroidism in the mother. Fetal and neonatal thyroid dysfunction is not common, but risk factors, such as high TRAb titers, should be evaluated in all pregnant hyperthyroid women. Hyperthyroidism may recur in the postpartum period as Graves disease or postpartum thyroiditis; thus, it is prudent to evaluate thyroid function 6 weeks after delivery. Preconception counseling and a multifaceted approach to care by the endocrinologist and the obstetric team are imperative for a successful pregnancy. A team effort is of paramount importance in the care of these women; the multidisciplinary approach including an endocrinologist, fetal-maternal specialist or obstetrician, neonatologist, pediatric endocrinologist, and anesthesiologist should be implemented during gestation.

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