**Core Concept**
The thioamide group of antithyroid drugs, including methimazole and propylthiouracil, is used to treat hyperthyroidism by inhibiting thyroid hormone synthesis. These medications target the enzyme thyroid peroxidase (TPO), which is crucial for the production of thyroid hormones.

**Why the Correct Answer is Right**
The correct answer is related to the adverse effects of thioamide antithyroid drugs. These medications can cause agranulocytosis, a potentially life-threatening decrease in white blood cells, as well as liver damage and rash. They can also cause gastrointestinal symptoms such as nausea and vomiting.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option might be a common adverse effect of thioamide antithyroid drugs, such as agranulocytosis or liver damage. However, we need to find the exception.
* **Option B:** This option is a known adverse effect of thioamide antithyroid drugs, such as rash or gastrointestinal symptoms.
* **Option C:** This option is a known adverse effect of thioamide antithyroid drugs, such as agranulocytosis or liver damage.

**Clinical Pearl / High-Yield Fact**
It is essential to monitor patients taking thioamide antithyroid drugs for signs of agranulocytosis, such as fever, sore throat, or mouth ulcers, and to educate patients about the potential for liver damage.

**Correct Answer: D.**