## **Core Concept**
Pendred's syndrome is a genetic disorder leading to congenital bilateral sensorineural hearing loss and goiter. It is associated with defects in the **SLC26A4** gene, which encodes for the pendrin protein. Pendrin plays a crucial role in the transport of iodide in the thyroid gland and in maintaining endolymphatic pH in the inner ear.

## **Why the Correct Answer is Right**
The correct answer, **SLC26A4**, is the gene responsible for encoding the pendrin protein. Mutations in this gene lead to Pendred's syndrome, characterized by hearing loss and thyroid abnormalities. Pendrin is crucial for iodide transport in the thyroid, explaining the association with goiter, and for maintaining the ionic composition and pH of the endolymph in the inner ear, which is vital for hearing.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately represent the gene associated with Pendred's syndrome.
- **Option B:** This option is incorrect as it does not correspond to the gene defect seen in Pendred's syndrome.
- **Option C:** This option is incorrect because, although some genetic disorders are associated with this chromosome, it is not specifically linked to Pendred's syndrome.
- **Option D:** This option is incorrect as it does not accurately represent the gene defect responsible for Pendred's syndrome.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Pendred's syndrome accounts for approximately 10% of hereditary hearing loss and is often associated with a positive family history of hearing loss and/or thyroid disease. A classic feature is the presence of a **goiter** (enlargement of the thyroid gland) in addition to hearing loss. Early diagnosis and management can significantly impact the quality of life for affected individuals.

## **Correct Answer:** .