What is the best management for a 14-week pregnant patient presenting with tremors, palpitations, diffuse thyromegaly, and a thyroid scan showing diffuse uptake and a cold nodule?

Management of Hyperthyroidism in a Pregnant Patient with a Cold Nodule

The best management for this 14-week pregnant patient with hyperthyroidism and a cold nodule is antithyroid drug therapy with propylthiouracil (PTU), with consideration for switching to methimazole after the first trimester.

Assessment of the Clinical Scenario

The patient presents with:

• 14 weeks of pregnancy
• Symptoms of hyperthyroidism (tremors, palpitations)
• Diffuse thyromegaly on examination
• Thyroid scan showing diffuse uptake with a cold nodule

Recommended Management Approach

First-Line Treatment

1. Initiate propylthiouracil (PTU) therapy immediately

   • PTU is preferred during the first trimester of pregnancy due to lower risk of congenital malformations compared to methimazole 1, 2
   • Consider switching to methimazole after the first trimester due to risk of maternal hepatotoxicity with continued PTU use 1, 3

2. Add beta-blocker therapy

   • Administer a beta-blocker to control symptoms (tremors, palpitations) and ventricular response rate 4
   • If beta-blockers are contraindicated, a non-dihydropyridine calcium channel antagonist (diltiazem or verapamil) can be used 4

3. Monitor thyroid function regularly

   • Maintain free T4 in the upper one-third of each trimester-specific reference interval 3
   • Adjust medication dose as needed throughout pregnancy 1

Cold Nodule Management

• Defer evaluation of the cold nodule until after delivery unless there are suspicious features requiring immediate attention 5
• Treatment of thyroid nodules can generally be safely postponed until after delivery 5

Why Other Options Are Not Appropriate

• Total thyroidectomy (option A): Surgery during pregnancy carries unnecessary risks and is reserved for cases where medical therapy fails or there is significant obstruction
• Excision of cold nodule then antithyroid drugs (option B): Unnecessary surgical intervention during pregnancy; medical management is first-line
• Radioiodine (option C): Absolutely contraindicated during pregnancy due to risk of fetal thyroid ablation 3
• External beam radiation (option D): Contraindicated during pregnancy due to risk of fetal harm

Monitoring and Follow-up

• Check thyroid function tests every 2-4 weeks initially, then monthly once stable
• Monitor for signs of hepatotoxicity with PTU (anorexia, pruritus, jaundice, right upper quadrant pain) 1
• Assess for adequate control of hyperthyroid symptoms
• Consider reducing medication dose in the third trimester as thyroid function may improve due to the immune-suppressant effects of pregnancy 6

Special Considerations

• If atrial fibrillation develops, anticoagulation with heparin (not warfarin) should be considered 4
• Untreated or inadequately treated hyperthyroidism increases risks of preeclampsia, preterm delivery, heart failure, and possibly miscarriage 4, 6
• The goal is to achieve and maintain euthyroidism throughout pregnancy to reduce maternal and fetal complications 5, 6

Pitfalls to Avoid

• Overtreating hyperthyroidism, which can lead to fetal hypothyroidism
• Undertreating hyperthyroidism, which can lead to maternal and fetal complications
• Failing to monitor liver function with PTU use
• Using radioactive iodine or performing unnecessary surgery during pregnancy