Autoimmune thyroiditis can be confirmed in a patient by
**Core Concept**
Autoimmune thyroiditis, including Hashimoto's thyroiditis and Graves' disease, is a condition in which the immune system mistakenly attacks the thyroid gland, leading to inflammation and damage. The underlying principle being tested is the diagnostic approach to confirm autoimmune thyroiditis.
**Why the Correct Answer is Right**
The correct answer is based on the detection of autoantibodies against thyroid peroxidase (TPO) and thyroglobulin (Tg), which are specific markers of autoimmune thyroiditis. These autoantibodies can be detected through blood tests, such as the thyroid antibody panel. The presence of these autoantibodies indicates an autoimmune response against the thyroid gland, confirming the diagnosis of autoimmune thyroiditis.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the diagnosis of autoimmune thyroiditis. While thyroid function tests (TFTs) can indicate hypothyroidism or hyperthyroidism, they do not confirm autoimmune thyroiditis.
* **Option B:** This option is incorrect because ultrasound findings may suggest thyroiditis, but they are not specific or diagnostic. Ultrasound can show thyroid gland enlargement, nodules, or cysts, but these findings can also be present in other conditions.
* **Option C:** This option is incorrect because thyroid-stimulating hormone (TSH) levels can be elevated or decreased in autoimmune thyroiditis, but they do not confirm the diagnosis. TSH levels can also be affected by other factors, such as medication or non-thyroidal illness.
**Clinical Pearl / High-Yield Fact**
The presence of thyroid autoantibodies (TPO and Tg) is a specific marker of autoimmune thyroiditis, and their detection is essential for confirming the diagnosis. These autoantibodies can also be used to monitor disease activity and response to treatment.
**Correct Answer:** D.