Hypothyroidism caused by a viral infection of the thyroid gland is a pathologic condition associated with which of the blood hormone levels.
**Core Concept**
The underlying principle being tested is the relationship between thyroid gland pathology and hormone levels, specifically in the context of hypothyroidism caused by viral infection, also known as **subacute thyroiditis** or **De Quervain's thyroiditis**. This condition leads to inflammation of the thyroid gland. The **thyroid-stimulating hormone (TSH)** and **thyroxine (T4)** levels are key indicators of thyroid function.
**Why the Correct Answer is Right**
In subacute thyroiditis, the thyroid gland is initially inflamed, leading to the release of pre-formed **thyroid hormones (T3 and T4)** into the bloodstream, causing a transient hyperthyroid phase. Following this, the gland becomes depleted of hormone, and a hypothyroid phase ensues, characterized by elevated **TSH** levels as the pituitary gland attempts to stimulate the thyroid to produce more hormone, and decreased **T4** levels due to the thyroid's reduced ability to produce hormone.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not accurately reflect the hormone levels during the hypothyroid phase of subacute thyroiditis.
**Option B:** Incorrect as it might represent the initial hyperthyroid phase but not the hypothyroid phase in question.
**Option C:** Incorrect because it does not align with the expected changes in TSH and T4 levels during hypothyroidism caused by thyroiditis.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that subacute thyroiditis can present with a triphasic pattern of thyroid function tests: an initial thyrotoxic phase due to hormone release, a subsequent hypothyroid phase as the gland is depleted, and finally, a return to euthyroidism as the inflammation resolves and thyroid function recovers.
**Correct Answer:** D. Elevated TSH, Low T4.