## **Core Concept**
Graves' disease is an autoimmune disorder that causes hyperthyroidism. Managing Graves' disease during pregnancy is crucial as it affects both the mother and the fetus. The treatment goals are to control symptoms, normalize thyroid function, and minimize risks to the fetus.

## **Why the Correct Answer is Right**
The correct answer, **Propylthiouracil (PTU)**, is often considered the first-line treatment for Graves' disease during the first trimester of pregnancy due to its lower risk of teratogenicity compared to methimazole. PTU works by inhibiting the synthesis of thyroid hormones through its action on thyroid peroxidase, an enzyme crucial for the production of thyroxine (T4) and triiodothyronine (T3).

## **Why Each Wrong Option is Incorrect**
- **Option A: Radioactive Iodine** - This is contraindicated in pregnancy due to the risk of ablating the fetal thyroid gland.
- **Option B: Methimazole** - Although effective, methimazole is generally avoided in the first trimester due to its association with congenital anomalies, such as esophageal atresia and choanal atresia. It may be considered after the first trimester if needed.
- **Option D: Iodine** - High doses of iodine can be used in some cases of hyperthyroidism but are not the preferred treatment for Graves' disease in pregnancy due to potential fetal risks and the availability of more targeted therapies like PTU.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the management of Graves' disease in pregnancy often involves switching between PTU and methimazole due to PTU's rare but serious side effect of liver toxicity. Monitoring liver function tests is crucial when using PTU.

## **Correct Answer: C. Propylthiouracil (PTU).**