What is the best management for a pregnant patient with symptoms suggestive of hyperthyroidism (excessive thyroid hormone production) and a thyroid scan showing diffuse uptake along with a cold nodule?

From the Guidelines

The best management for a pregnant patient with symptoms of hyperthyroidism and a thyroid scan showing diffuse uptake with a cold nodule involves prompt initiation of antithyroid medications, specifically propylthiouracil (PTU) during the first trimester, followed by methimazole for the remainder of pregnancy. This approach is based on the most recent and highest quality evidence available, which prioritizes minimizing risks to the fetus while effectively managing the mother's condition 1. Key considerations include:

• Initiating PTU at doses of 100-150 mg three times daily during the first trimester, then transitioning to methimazole 10-20 mg daily after the first trimester due to its lower risk of birth defects 1.
• Using beta-blockers such as propranolol (10-40 mg three to four times daily) for short-term symptom control if necessary 1.
• Regular monitoring of thyroid function tests every 2-4 weeks initially, then monthly once stabilized, aiming to maintain free T4 in the upper normal range 1.
• Avoiding radioactive iodine scanning and treatment during pregnancy due to the risk of fetal thyroid damage 1. The cold nodule found on the thyroid scan requires consideration for fine needle aspiration to rule out malignancy, but this can typically be deferred until after delivery unless there are concerning features 1. This management strategy balances the need for maternal symptom control with fetal safety, recognizing that untreated hyperthyroidism poses significant risks including preeclampsia, preterm birth, and fetal growth restriction 1.

From the FDA Drug Label

In pregnant women with untreated or inadequately treated Graves’ disease, there is an increased risk of adverse events of maternal heart failure, spontaneous abortion, preterm birth, stillbirth and fetal or neonatal hyperthyroidism Because methimazole crosses placental membranes and can induce goiter and cretinism in the developing fetus, hyperthyroidism should be closely monitored in pregnant women and treatment adjusted such that a sufficient, but not excessive, dose be given during pregnancy In many pregnant women, the thyroid dysfunction diminishes as the pregnancy proceeds; consequently, a reduction of dosage may be possible. In some instances, anti-thyroid therapy can be discontinued several weeks or months before delivery Due to the rare occurrence of congenital malformations associated with methimazole use, it may be appropriate to use an alternative anti-thyroid medication in pregnant women requiring treatment for hyperthyroidism particularly in the first trimester of pregnancy during organogenesis. Given the potential maternal adverse effects of propylthiouracil (e.g., hepatotoxicity), it may be preferable to switch from propylthiouracil to methimazole for the second and third trimesters.

The best management for a pregnant patient with symptoms suggestive of hyperthyroidism and a thyroid scan showing diffuse uptake along with a cold nodule is to use antithyroid drugs.

• The patient is 14 weeks pregnant, which means she is in her second trimester.
• Considering the potential risks and benefits, methimazole may be a suitable option for this patient, as it is preferred over propylthiouracil in the second and third trimesters due to the risk of hepatotoxicity associated with propylthiouracil 2.
• The treatment should be closely monitored, and the dosage adjusted to ensure a sufficient but not excessive dose is given during pregnancy.
• Surgery (total thyroidectomy or excision of the cold nodule) may not be the best initial option, as it carries its own risks, especially during pregnancy.
• Radio-iodine is contraindicated in pregnancy due to the risk of radioactive iodine crossing the placenta and damaging the fetal thyroid gland.
• External beam radiation is not a standard treatment for hyperthyroidism and is not recommended in this scenario.

From the Research

Management of Hyperthyroidism in Pregnancy

The patient's symptoms of tremors, palpitations, and diffuse thyromegaly, along with a thyroid scan showing diffuse uptake and a cold nodule, suggest hyperthyroidism, likely due to Graves' disease.

• The primary goal is to manage hyperthyroidism while minimizing risks to the fetus.
• Antithyroid drugs, such as methimazole (MMI) and propylthiouracil (PTU), are the cornerstone of treatment for hyperthyroidism in pregnancy, as they can inhibit thyroid hormone synthesis 3, 4, 5.
• Between MMI and PTU, PTU is often preferred during the first 16 weeks of gestation due to its lower risk of teratogenic effects, such as aplasia cutis and choanal/esophageal atresia 3, 6, 5.
• Radio-iodine therapy is contraindicated during pregnancy due to the risk of radioactive iodine crossing the placenta and damaging the fetal thyroid gland 4.
• Thyroidectomy may be considered in severe cases of hyperthyroidism that are unresponsive to antithyroid drugs, but it is not the first line of treatment 4.
• The presence of a cold nodule does not necessarily require immediate excision, especially during pregnancy, unless it is suspected to be malignant or causing significant symptoms.

Treatment Options

• Given the patient's pregnancy and symptoms, the best initial management would be to start antithyroid drugs, with PTU being a preferred option during the first 16 weeks of gestation 3, 6, 5.
• The cold nodule can be monitored, and its management can be reassessed post-pregnancy.
• Total thyroidectomy (option a) and external beam radiation (option d) are not the preferred initial treatments for hyperthyroidism in pregnancy.
• Excision of the cold nodule followed by antithyroid drugs (option b) might be considered if the nodule is suspected to be malignant or causing significant symptoms, but it is not the first line of treatment.
• Radio-iodine (option c) is contraindicated during pregnancy.