What is the most likely treatment for a pregnant woman in her 2nd trimester (14 weeks gestation) with symptoms of hyperthyroidism, including tremors, palpitations, and right neck swelling?

From the Guidelines

For a pregnant woman in her 2nd trimester (14 weeks) with hyperthyroidism symptoms, including tremors, palpitations, and right neck swelling, the most likely treatment is antithyroid drugs, specifically propylthiouracil (PTU) or methimazole, with consideration to switch from PTU to methimazole after the first trimester. The choice between PTU and methimazole depends on the gestational age and the balance between the risks of congenital abnormalities associated with methimazole and the risk of maternal liver complications associated with PTU 1.

Treatment Approach

• The typical starting dose of PTU is 100-150 mg three times daily, adjusted based on thyroid function tests.
• For methimazole, the starting dose is often 10-20 mg daily.
• The goal is to maintain maternal free T4 levels in the upper normal range using the lowest effective dose of antithyroid medication.
• Regular monitoring of thyroid function every 2-4 weeks is essential, with dose adjustments as needed.
• Beta-blockers like propranolol (10-40 mg three to four times daily) can be used temporarily to manage symptoms such as tremors and palpitations.

Considerations

• The right neck swelling suggests a possible thyroid nodule or goiter, which should be evaluated with ultrasound.
• Hyperthyroidism treatment during pregnancy aims to control maternal symptoms while minimizing fetal risk, as both PTU and methimazole cross the placenta.
• PTU is preferred in early pregnancy due to the lower risk of rare congenital abnormalities associated with methimazole, while methimazole is often preferred later due to the lower risk of maternal liver complications 1.

Management of Hyperthyroidism in Pregnancy

• Thyroidectomy may be considered for women who do not respond to thioamide therapy or have a large goiter causing symptoms, but it is typically reserved for the second trimester 1.
• Radioiodine (I-131) is contraindicated in pregnant women due to the risk of inducing congenital hypothyroidism in the fetus 1.

Given the patient's gestational age of 14 weeks, transitioning to methimazole may be appropriate, considering the balance of risks and benefits. However, the decision should be made on a case-by-case basis, taking into account the patient's specific condition, the severity of her symptoms, and her response to initial treatment. Regular follow-up and monitoring of both the mother and the fetus are crucial to ensure the best possible outcomes.

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 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 most likely treatment for a pregnant woman in her 2nd trimester (14 weeks gestation) with symptoms of hyperthyroidism is Antithyroid drugs, specifically Methimazole as it is preferred over propylthiouracil in the second and third trimesters due to the potential hepatotoxicity of propylthiouracil 2.

From the Research

Treatment Options for Hyperthyroidism in Pregnancy

The most likely treatment for a pregnant woman in her 2nd trimester (14 weeks gestation) with symptoms of hyperthyroidism, including tremors, palpitations, and right neck swelling, is:

• Antithyroid drugs, specifically Propylthiouracil (PTU), as it is considered the least teratogenic option 3, 4, 5

Rationale for Treatment Choice

• PTU is preferred over Methimazole (MMI) due to its lower risk of congenital anomalies 4
• Antithyroid drugs are the main therapy for maternal hyperthyroidism, and PTU is recommended in the first trimester and can be continued in the second trimester 5
• The goal of treatment is to maintain free thyroxine concentration in the upper one-third of each trimester-specific reference interval 5

Alternative Treatment Options

• Thyroidectomy may be necessary in few cases of hyperthyroidism during pregnancy, with the optimal time for surgery during the second trimester 6
• Radioiodine therapy is not recommended during pregnancy due to the risk of fetal thyroid damage 7, 5