**Core Concept**
Dysthyroid eye disease, also known as Graves' ophthalmopathy, is an autoimmune inflammatory condition associated with Graves' disease, which affects the tissues around the eye. The condition is characterized by orbital inflammation, edema, and fibrosis leading to proptosis, eyelid retraction, and diplopia.

**Why the Correct Answer is Right**
Graves' ophthalmopathy is thought to result from the autoimmune response to the orbital tissues, which are exposed to the circulating autoantibodies against the thyroid-stimulating hormone receptor (TSHR). This leads to orbital inflammation and fibrosis, causing the characteristic symptoms of proptosis, eyelid retraction, and diplopia. The inflammation is mediated by various cytokines, including tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1β), which play a crucial role in the pathogenesis of the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the pathogenesis of Graves' ophthalmopathy. The condition is not simply a result of increased thyroid hormone levels, but rather an autoimmune response to the orbital tissues.

**Option B:** This option is incorrect because it is not a true statement about Graves' ophthalmopathy. The condition is not primarily caused by a viral infection, but rather by an autoimmune response.

**Option C:** This option is incorrect because it is not a true statement about Graves' ophthalmopathy. The condition is not primarily caused by a tumor, but rather by an autoimmune response to the orbital tissues.

**Clinical Pearl / High-Yield Fact**
A key feature of Graves' ophthalmopathy is the presence of extraocular muscle enlargement, which can lead to diplopia. This is due to the autoimmune response to the extraocular muscles, which are exposed to the circulating autoantibodies against the TSHR.

**Correct Answer:** D.