From the Guidelines
For a pregnant woman at 28 weeks gestation with hyperthyroidism on 15mg carbimazole who is still symptomatic with biochemical evidence of thyrotoxicosis (low TSH, elevated T3 and T4), the most appropriate management is to increase her carbimazole dose to 20-30mg daily, with close monitoring every 2-4 weeks. This approach is based on the goal of maintaining maternal free T4 in the upper normal range or slightly elevated, using the lowest effective dose of antithyroid medication, as recommended by the American College of Obstetricians and Gynecologists (ACOG) 1. The use of carbimazole is acceptable after the first trimester, and increasing the dose is necessary to control the symptoms of hyperthyroidism, as indicated by the low TSH and high T3 and T4 levels. Monitoring should include thyroid function tests (TSH, free T4, free T3) and assessment for side effects such as rash, fever, sore throat, or abnormal liver function, as noted in the ACOG practice bulletin on thyroid disease in pregnancy 1. Additionally, fetal growth and well-being should be monitored with regular ultrasounds, and beta-blockers like propranolol can be added temporarily at the lowest effective dose (10-40mg three times daily) to control maternal symptoms such as palpitations and tremor, as suggested by the guidelines for managing hyperthyroidism in pregnancy 1. This management approach aims to control maternal hyperthyroidism while minimizing risks to the fetus, as untreated maternal hyperthyroidism can lead to complications including preterm birth, low birth weight, preeclampsia, and fetal thyroid dysfunction. Key considerations in managing hyperthyroidism in pregnancy include:
- Maintaining euthyroidism to minimize risks to the mother and fetus
- Using the lowest effective dose of antithyroid medication
- Monitoring for side effects and adjusting the treatment plan as needed
- Considering the risks and benefits of different treatment options, including propylthiouracil (PTU) and carbimazole, as discussed in the guidelines for preconception counseling and care 1.
From the Research
Management of Hyperthyroidism in Pregnancy
The management of hyperthyroidism in a pregnant lady at 28 weeks gestation, currently on 15mg carbimazole, presenting with symptoms of hyperthyroidism, low TSH, and elevated T3 and T4 levels, requires careful consideration of the potential risks and benefits of different treatment options.
Treatment Options
- Increase carbimazole dose: Increasing the dose of carbimazole to 20mg may be considered to achieve euthyroidism, as seen in a case report where a patient's dose was increased to 20mg thrice daily 2.
- Switch to Propylthiouracil (PTU): Switching to PTU may be considered, especially in the third trimester, as it is preferred in this trimester due to the potential risks of carbimazole 3.
- Referral for thyroidectomy: Referral for thyroidectomy may be considered in cases where medical management is not effective or feasible, as seen in a case report where a patient underwent thyroidectomy due to carbimazole resistance 2.
Considerations for Treatment
- Fetal thyroid status: The treatment should aim to maintain fetal thyroid status within normal limits, as fetal hypothyroidism can occur with both PTU and methimazole (MMI) 4.
- Maternal and fetal risks: The treatment should balance the risks of uncontrolled hyperthyroidism with the potential risks of antithyroid drugs, such as hepatotoxicity with PTU and choanal and esophageal atresia with MMI 3.
- Monitoring and adjustment: Regular monitoring of maternal and fetal thyroid function and adjustment of treatment as needed is crucial to prevent adverse effects on the mother, fetus, and neonate 5, 3.