Muscle to be affected commonly in thyroid ophthalmopathy is:
**Core Concept**
Thyroid ophthalmopathy, also known as Graves' orbitopathy, is a condition characterized by inflammation and swelling of the tissues around the eye, particularly the extraocular muscles and orbital fat. This condition is a common complication of Graves' disease, an autoimmune disorder that affects the thyroid gland.
**Why the Correct Answer is Right**
The extraocular muscles, particularly the medial rectus muscle, are commonly affected in thyroid ophthalmopathy. This is due to the infiltration of immune cells and the deposition of mucopolysaccharides, leading to swelling and inflammation of the muscles. The medial rectus muscle is responsible for eye movement, and its involvement can cause symptoms such as diplopia (double vision) and restricted eye movements.
**Why Each Wrong Option is Incorrect**
* **Option A:** The levator palpebrae superioris muscle is responsible for eyelid elevation, and its involvement is less common in thyroid ophthalmopathy.
* **Option B:** The superior oblique muscle is responsible for intorsion and depression of the eye, and its involvement is not typically associated with thyroid ophthalmopathy.
* **Option C:** The inferior oblique muscle is responsible for extorsion and elevation of the eye, and its involvement is not commonly seen in thyroid ophthalmopathy.
**Clinical Pearl / High-Yield Fact**
The medial rectus muscle is often the most affected extraocular muscle in thyroid ophthalmopathy, leading to symptoms such as diplopia and restricted eye movements.
**Correct Answer:** C.