There was a sudden increases in the size of Thyroid swelling along with pain. Most likely cause is
**Core Concept**
Thyroid swelling, also known as goiter, can result from various causes, including iodine deficiency, thyroiditis, or neoplastic processes. A sudden increase in size, accompanied by pain, suggests a more acute or inflammatory etiology.
**Why the Correct Answer is Right**
The rapid enlargement of the thyroid gland with pain is most likely due to subacute thyroiditis, a condition characterized by inflammation of the thyroid gland. This condition often follows a viral infection and is associated with the release of preformed thyroid hormones, leading to a transient hyperthyroid state. The pain is thought to be due to the inflammation of the thyroid gland and the surrounding tissues. The condition can be self-limiting, but treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) and sometimes corticosteroids may be necessary to alleviate symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** While iodine deficiency can cause goiter, it typically leads to a gradual enlargement of the thyroid gland over time, rather than a sudden increase in size with pain.
**Option B:** Thyroid neoplasms can cause a rapid increase in thyroid size, but they are less likely to be painful in the early stages.
**Option C:** Riedel's thyroiditis is a rare form of thyroiditis characterized by a hard, fibrotic thyroid gland. While it can cause a rapid increase in thyroid size, it is typically painless.
**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between subacute thyroiditis and other causes of thyroid swelling, as the management and prognosis differ significantly.
**Correct Answer: D. Subacute thyroiditis.**