Graves Hyperthyroidism and Pregnancy: A Clinical Update

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


Endocr Pract. 2010;16(1):118-129. 

In This Article

Prepregnancy Counseling

Prepregnancy counseling for all patients with hyperthyroidism or a history of hyperthyroidism is imperative. Multiple fetal and maternal complications may occur if hyperthyroidism is not adequately managed during pregnancy. Before conception, a hyperthyroid patient may be offered ablative therapy by iodine 131 (131I) or surgery for definitive treatment or medical therapy.

Ablative Therapy

If the patient opts for ablative therapy, the following recommendations should be made:

  1. Pregnancy test before 131I ablation to avoid radiation exposure to the fetus.

  2. Delay of conception on average of 3 to 6 months until the levothyroxine dosage has been adjusted to achieve a target thyrotropin (TSH) value for pregnancy (0.3–2.5 mIU/L).

  3. Determination of TSH receptor antibodies (TRAb); the gradual disappearance from the circulation depends on the type of treatment. After thyroidectomy, a gradual disappearance of TRAb titers occurs, while after 131I therapy, an increase in TRAb titer may last for 12 months followed by a gradual fall in titers. Therefore, in women contemplating pregnancy who have high TRAb titers, surgery appears to be the therapy of choice.[11]

  4. Adjustment of levothyroxine dosage early in pregnancy because of the increased T4 requirement during the first trimester; the required dosage may be greater than that used to treat women with hypothyroidism due to other etiologies.

Antithyroid Drugs

If the antithyroid drugs are chosen, the patient requires counseling regarding the following:

  1. Risks associated with both PTU and methimazole—methimazole is the drug of choice, but only PTU is used in the first trimester of pregnancy because of the risk of methimazole-related embryopathy.

  2. Importance of close follow-up throughout pregnancy with frequent blood tests and adjustment of antithyroid drugs because decreases in drug dosages are commonly required.

  3. Recommendations regarding breastfeeding while taking antithyroid drugs.

  4. Determination of TRAb antibody status between 24 to 28 weeks' gestation to assess risk of fetal and/or neonatal hyperthyroidism.

  5. Need for fetal testing to assess well-being by perinatologist or obstetrician.

  6. Possibility of disease aggravation in the first trimester and recurrence in the postpartum period due to postpartum thyroiditis or recurrent Graves disease.[12]