SARS-CoV-2 Affects Thyroid and Adrenal Glands: An 18F-FDG PET/CT Study

Abstract

Background: Since most endocrine glands express ACE-2 receptors and can be infected by SARS-CoV-2 virus, this retrospective multicentre observational study aims to assess the metabolic activity of thyroid and adrenal glands of COVID-19 patients by ¹⁸F-FDG PET/CT.

Methods: We retrospectively evaluated the ¹⁸F-FDG PET/CT scans of COVID-19 patients admitted by three different centres, either in a low-intensity department or in the intensive care unit (ICU). A visual assessment and a semi-quantitative evaluation of areas of interest in thyroid and adrenal glands were performed by recording SUVmax and SUVmean. The ¹⁸F-FDG PET/CT uptake in COVID-19 patients was compared with those observed in normal age-matched controls.

Results: Between March 2020 and March 2022, 33 patients from three different centres (twenty-eight patients in a low-intensity department and five patients in ICU), were studied by ¹⁸F-FDG PET/CT during active illness. Seven of them were also studied after clinical remission (3-6 months after disease onset). Thirty-six normal subjects were used as age-matched controls. In the thyroid gland, no statistically significant differences were observed between control subjects and COVID-19 patients at diagnosis. However, at the follow-up PET/CT study, we found a statistically higher SUVmax and SUVmean (p = 0.009 and p = 0.004, respectively) in the thyroid of COVID-19 patients. In adrenal glands, we observed lower SUVmax and SUVmean in COVID-19 patients at baseline compared to control subjects (p < 0.0001) and this finding did not normalize after clinical recovery (p = 0.0018 for SUVmax and p = 0.002 for SUV mean).

Conclusions: In our series, we observed persistent low ¹⁸F-FDG uptake in adrenal glands of patients at diagnosis of COVID-19 and after recovery, suggesting a chronic hypofunction. By contrast, thyroid uptake was comparable to normal subjects at disease onset, but after recovery, a subgroup of patients showed an increased metabolism, thus possibly suggesting the onset of an inflammatory thyroiditis. Our results should alert clinicians to investigate the pituitary-adrenal axis and thyroid functionality at the time of infection and to monitor them after recovery.

Keywords: 18F-FDG PET/CT; COVID-19 patients; ICU; SARS-CoV-2; adrenal glands; thyroid gland.

Figure 1

Example of calculation of quantitative parameters on thyroid gland of one COVID-19 patient. Yellow circles and arrows show the regions of interest drawn on thyroid tissue. In this patient, the right lobe had an SUVmax of 2.18 and an SUVmean of 2.05; the left lobe had an SUVmax of 2.10 and an SUVmean of 1.94.

Figure 2

Boxplots and violin plots of SUVmax in thyroid glands of control group vs. COVID-19 patients at the diagnosis and distribution of SUVmax of COVID-19 patients according to the cut-off.

Figure 3

Boxplots and violin plots of SUVmean in thyroid glands of control group vs. COVID-19 patients at the diagnosis and distribution of SUVmean of COVID-19 patients according to the cut-off.

Figure 4

Example of calculation of quantitative parameters on adrenal glands of one COVID-19 patient. Yellow circles and arrows show the regions of interest. In this patient, the right adrenal gland had an SUVmax of 1.33 and an SUVmean of 1.21; the left adrenal gland had an SUVmax of 1.26 and an SUVmean of 1.20.

Figure 5

Boxplots and violin plots of SUVmax in adrenal glands of control group vs. COVID-19 patients at the diagnosis and distribution of SUVmax of COVID-19 patients according to the cut-off.

Figure 6

Boxplots and violin plots of SUVmean in adrenal glands of control group vs. COVID-19 patients at the diagnosis and distribution of SUVmean of COVID-19 patients according to the cut-off.