Which diagnosis is most likely in a patient who develops a painful, tender thyroid after a recent viral infection?

• A. Hashimoto's
• B. Graves'
• C. Subacute Thyroiditis
• D. Riedel Thyroiditis

Answer: (C)

Subacute thyroiditis (De Quervain) is most likely here because a painful, tender thyroid after a recent viral infection is classic for an inflammatory thyroiditis triggered by a viral illness. The inflammation makes the gland tender and can be accompanied by fever and malaise. In the initial phase, damage to thyroid follicles releases preformed thyroid hormone, leading to a transient thyrotoxic state with symptoms like palpitations and heat intolerance. Lab-wise, you’d expect a low TSH with elevated free T4 and increased inflammatory markers such as ESR. Over weeks to months, the gland often becomes hypocritical as it recovers, and many patients experience a transient hypothyroid phase before returning to normal.

This differs from Hashimoto's, which is typically painless and autoimmune-driven, progressing to hypothyroidism rather than causing a painful, inflamed gland after an infection. Graves' disease, while causing thyrotoxicosis, presents with a non-tender diffuse goiter and often eye findings, not a tender post-viral thyroiditis. Riedel’s thyroiditis features a hard, rock-like, painless thyroid due to fibrous tissue replacement, not the tender inflammatory process seen after a viral illness.