Subacute thyroiditis is an inflammatory disease of the thyroid gland. Clinical manifestations include pain or discomfort in the neck, a painful diffuse goiter, and a transient episode of hyperthyroidism. We describe the case of a 48-year-old woman who had no symptoms characteristic of subacute thyroiditis. The test results were consistent with a clinical diagnosis of secondary hypothyroidism. The patient had a history of asymptomatic COVID-19 episode 6 months ago and neck pain one month ago. This case demonstrates the importance of a detailed history, comprehensive examination, and correct interpretation of laboratory and instrumental findings in making the diagnosis.