Endocrine Abstracts

Introduction

Patients who are critically ill can have alterations of thyroid function tests, known as non-thyroidal illness syndrome (NTIS). Moroever thyrotoxicosis can result from SARS-CoV-2 directly infecting the thyroid gland, as described in other viral infections. We report a case of hyperthyroidism diagnosed in a patient hospitalized for COVID-19 severe hypoxemic pneumonia.

Observation

A 78-year-old patient admitted to the COVID Unit for pneumonia related to COVID-19. On clinical examination, there was no sign of hyperthyroidism or pain on palpation of the thyroid. In biology, the TSH level was at 0.07 mU/l and the FT4 level was at 16.1 pmol/l (NR: 6-14). There were no arrhythmias on the electrocardiogram. The diagnosis of subacute thyroiditis related to COVID-19 was made and the patient was put on a low dose of methimazole.

Discussion

The most likely diagnosis was subacute thyroiditis related to COVID-19. The subacute thyroiditis is characterized by self-limiting thyrotoxicosis of variable duration, lasting a period of weeks or months, followed by hypothyroidism with final restoration of euthyroidism. However, the likelihood of pre-existing hyperthyroidism discovered incidentally is not ruled out in this case. There may be a direct effect of SARS-CoV-2 on thyroid function, potentially leading to exacerbation of preexisting autoimmune thyroid disease. The immunological investigation was postponed in our patient. A thyroid ultrasound and a thyroid scintigraphy would be scheduled after improvement of his condition. FT4 was not as high as the level of suppression of TSH, which can be explained by the coexistence of a NTIS. The decision to prescribe antithyroid drug was based on the age of the patient and the stage of hyperthyroidism. The stage II of hyperthyroidism (TSH < 0.1 mU/l) in patients older than 65 years should be treated according to the 2015 ATA Guidelines. Arrhythmias are not uncommon in COVID-19 patients related to COVID-19 myocarditis. This risk of arrhythmias may be increased by hyperthyroidism, another argument to prescribe antithyroid drug in this case.

Conclusion

This case presented both diagnostic and therapeutic challenges. The most likely diagnosis is subacute thyroiditis secondary to COVID-19. Despite the fact that hyperthyroidism is believed to be transient in this case, antithyroid drug were prescribed for several reasons.