## Core Concept
Hashimoto's thyroiditis is a chronic autoimmune thyroiditis characterized by lymphocytic infiltration of the thyroid gland, leading to thyroid dysfunction. It is a common cause of hypothyroidism in iodine-sufficient areas. The condition involves cell-mediated immunity and the production of thyroid-specific autoantibodies.

## Why the Correct Answer is Right
The correct answer, option D, is associated with a statement that does not hold true for Hashimoto's thyroiditis. Typically, Hashimoto's thyroiditis is associated with elevated levels of thyroid peroxidase antibodies (TPOAb) and sometimes thyroglobulin antibodies (TgAb). The condition often leads to hypothyroidism, and its diagnosis is based on clinical findings, laboratory tests including TSH, free T4, and thyroid autoantibodies.

## Why Each Wrong Option is Incorrect
- **Option A:** Typically, Hashimoto's thyroiditis is associated with an increased risk of other autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, and pernicious anemia. Therefore, stating that it is not associated with other autoimmune diseases would be incorrect.
- **Option B:** Hashimoto's thyroiditis often presents with a diffusely enlarged thyroid gland, and it is characterized by lymphocytic infiltration. Hence, a statement suggesting it does not cause thyroid gland enlargement would be incorrect.
- **Option C:** The presence of thyroid autoantibodies (like TPOAb and TgAb) is a hallmark of Hashimoto's thyroiditis. Therefore, suggesting that autoantibodies are not involved would be incorrect.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that Hashimoto's thyroiditis can present in different phases, including a transient phase of thyrotoxicosis (due to thyroiditis) before progressing to hypothyroidism. This variability in presentation can make diagnosis challenging.

## Correct Answer Line
**Correct Answer: D.**