The role of PET/CT in thyroid autoimmune diseases.

Autoimmune thyroid diseases (AITD) are a heterogeneous group of disorders. They include, in particular, Graves' disease and Hashimoto's thyroiditis with a wide range of different functional status ranging from subclinical biochemical abnormalities to severe hyperthyroidism or severe hypothyroidism respectively. Furthermore, other conditions more frequently infectious or drug related can cause an immune reaction in the thyroid tissue. In AITDs, positron emission tomography/computed tomography (PET/CT) does not play a primary role for disease diagnosis or management, but accidental findings can occur in both symptomatic and asymptomatic patients, and they should be recognized and well interpreted. A comprehensive literature search of the PubMed databases was conducted to identify papers (systematic review, prospective and retrospective study, case report) evaluating the role of PET/CT in thyroid autoimmune diseases. Thyroid diffuse uptake of 18F-fluoro-2-deoxy-2-d-glucose ([18F]FDG) has been shown to be frequently associated with AITDs, but also with immune-induced thyroid disorders related to SARS-CoV-2 or immunotherapy, while malignant lesions more often have a focal aspect. Other radiopharmaceuticals as [68Ga]-DOTA-peptides, [68Ga]-fibroblast activation protein inhibitors (FAPIs) and [68Ga]-prostate specific membrane antigen ([68Ga]-PSMA) showed similar findings. In conclusion, PET/CT scan in AITDs does not play a primary role in the diagnosis, but the occasional finding of a thyroid uptake must always be described in the report and possibly investigated for a better patient's management.

COVID-19 and Aspiration Pneumonia: Similar Pulmonary Findings with Different Diagnoses-a Pitfall in [18F]FDG PET/CT.

Since December 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a worldwide pandemic. Especially in the centers most affected by the pandemic, symptoms (such as fever, cough, myalgia, or fatigue) and/or radiological signs (such as ground-glass opacity) typically related to COVID-19 often diverted clinicians' attention from other diseases. Despite the urgency to recognize and cure SARS-CoV-2 infection, a plethora of differential diagnoses must be considered, and other diseases must be equally and promptly treated, as described in this case report.

SARS-COV-2-related immune-inflammatory thyroid disorders: facts and perspectives.

Introduction: During the COVID-19 pandemic thyroid gland alteration/dysfunction has been emerged as a possible endocrine complication. The present review is focused on inflammatory and autoimmune thyroid complications triggered by SARS-CoV-2 infection by searching through databases like MEDLINE and Scopus up to April 2021.Areas covered: Beside the occurrence of 'non-thyroidal illness' in severe clinical conditions, alterations of thyroid function and structure may occur during COVID-19 as a consequence of either direct or indirect effects of SARS-CoV-2 infection on the gland. On the one hand, SARS-CoV-2 uses ACE2 as a receptor to infect the host cells and ACE2 is highly expressed by follicular thyroid cells. On the other hand, COVID-19 is associated with a systemic inflammatory and immune response, involving Th1/Th17/Th2 lymphocytes and proinflammatory cytokines, which resembles the immune activation that occurs in immune-mediated thyroid diseases. COVID-19-related thyroid disorders include destructive thyroiditis and onset or relapse of autoimmune thyroid disorders, leading to a broad spectrum of thyroid dysfunction ranging from thyrotoxicosis to hypothyroidism, that may worsen COVID-19 clinical course and affect prognosis.Expert opinion: Physicians should be aware of the possible occurrence of thyroid dysfunction during and after SARS-CoV-2 infection. Further longitudinal studies are warranted to evaluate potential long-term sequelae.

Prevalence of thyroid dysfunction in patients with COVID-19: a systematic review.

PURPOSE: Currently, there is an increasing interest regarding the impact of COVID-19 on the thyroid function. As several recent reports have described the onset of thyroid dysfunction in patients diagnosed with COVID-19, we performed a systematic review to assess the prevalence of thyroid dysfunction in patients with COVID-19 as this information could be clinically relevant for the management of these patients. METHODS: A comprehensive computer literature search using PubMed/Medline and Cochrane databases was performed until November 14, 2020 to search original articles evaluating thyroid dysfunction in COVID-19 patients. Information about thyroid dysfunction assessed by thyroid function test was retrieved by the eligible articles. Qualitative analysis (systematic review) only was performed whether a significant heterogeneity of data was detected. RESULTS: Seven studies including 1237 patients with COVID-19 were included. A significant heterogeneity across the studies was found. Most COVID-19 patients were euthyroid with TSH levels in the normal range (from 44 to 94% of the COVID-19 patients assessed in the included studies). The prevalence of thyroid dysfunction in COVID-19 patients (defined as abnormal thyroid function tests) largely varies among the included studies between 13 and 64% of COVID-19 patients as well as clinical presentation. A positive correlation between thyroid dysfunction and clinical severity of COVID-19 was reported. CONCLUSION: Literature data show that thyroid dysfunction is present in a significant percentage of patients with COVID-19. Assessment of thyroid function may be considered in symptomatic COVID-19 patients to have a baseline before introducing thyroid-interfering drugs and those requiring high-intensity care. Further, well-designed studies are needed to better elucidate the impact of COVID-19 on thyroid function and inform thyroid function testing and thyroid dysfunction management in COVID-19 patients.

Prevalence of interstitial pneumonia suggestive of COVID-19 at 18F-FDG PET/CT in oncological asymptomatic patients in a high prevalence country during pandemic period: a national multi-centric retrospective study.

PURPOSE: To assess the presence and pattern of incidental interstitial lung alterations suspicious of COVID-19 on fluorine-18-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT) ([18F]FDG PET/CT) in asymptomatic oncological patients during the period of active COVID-19 in a country with high prevalence of the virus. METHODS: This is a multi-center retrospective observational study involving 59 Italian centers. We retrospectively reviewed the prevalence of interstitial pneumonia detected during the COVID period (between March 16 and 27, 2020) and compared to a pre-COVID period (January-February 2020) and a control time (in 2019). The diagnosis of interstitial pneumonia was done considering lung alterations of CT of PET. RESULTS: Overall, [18F]FDG PET/CT was performed on 4008 patients in the COVID period, 19,267 in the pre-COVID period, and 5513 in the control period. The rate of interstitial pneumonia suspicious for COVID-19 was significantly higher during the COVID period (7.1%) compared with that found in the pre-COVID (5.35%) and control periods (5.15%) (p < 0.001). Instead, no significant difference among pre-COVID and control periods was present. The prevalence of interstitial pneumonia detected at PET/CT was directly associated with geographic virus diffusion, with the higher rate in Northern Italy. Among 284 interstitial pneumonia detected during COVID period, 169 (59%) were FDG-avid (average SUVmax of 4.1). CONCLUSIONS: A significant increase of interstitial pneumonia incidentally detected with [18F]FDG PET/CT has been demonstrated during the COVID-19 pandemic. A majority of interstitial pneumonia were FDG-avid. Our results underlined the importance of paying attention to incidental CT findings of pneumonia detected at PET/CT, and these reports might help to recognize early COVID-19 cases guiding the subsequent management.