Post COVID Thyroiditis as Documented on Tc-99m Pertechnetate Thyroid Scan

ABSTRACT

Aim/Introduction: The etiology of SAT (subacute thyroiditis) is presumed to be usually viral (most commonly associated viruses include enterovirus, coxsackievirus, mumps, measles, and adenovirus). In this pandemic era, prevalence of SAT associated with the COVID 19 seems to be increasing either during or after the course of disease, characterized by neck pain or discomfort, goiter and transient hyperthyroidism. However, this is usually missed due to the wide spectrum of COVID syndrome, and a simple thyroid scan can be instrumental in diagnosing related thyroiditis. Material(s) and Method(s) We report 3 (1 male, 2 females) cases of thyroiditis detected using Tc99m pertechnetate scan. Thyroid scan was done 20 minutes after injection of 5 milicuries (170 MBq) of Tc99m pertechnetate and planar images were acquired. Result(s) 3 (1 male, 2 females) cases of thyroiditis detected using Tc99m pertechnetate scan. Mean age was 36.3 years. Symptoms such as goiter (n=1), neck pain and tenderness (n=2), weakness and fatiguability (n=3), palpitations (n=2), heat intolerance (n=1), restlessness (n=2) were observed along with raised T3, T4 hormone levels and suppressed TSH, 3-4 months after COVID infection (mean duration 3.3 months). Other possible causes of thyroiditis and drug interference were ruled out. Thyroid scan images revealed faint or absent tracer uptake in thyroid gland. Conclusion(s) The affinity of SARS-Cov-2 to the thyroid gland has been presumed via the ACE2 receptors which are more prevalent in thyroid cells than lung cells. Inflammatory response and apoptosis is another proposed factor. Ultrasound will show a normal or enlarged thyroid but typically, diffusely, or focally hypoechogenic, and the color Doppler sonography will demonstrate low flow but thyroid scan is easier to perform, is less user dependent and carries more diagnostic value. COVID related thyroiditis can present months after infection and is a part of long COVID syndrome. Possibility of post immunization also exists. Thyroid scan can be widely used in these scenarios.