The COVID-19 pandemic has revealed a significant association between SARS-CoV-2 infection and diabetes, whereby individuals with diabetes are more susceptible to severe disease and higher mortality rates. Interestingly, recent findings suggest a reciprocal relationship between COVID-19 and diabetes, wherein COVID-19 may contribute to developing new-onset diabetes and worsen existing metabolic abnormalities. This narrative review aims to shed light on the intricate molecular mechanisms underlying the diabetogenic effects of COVID-19. Specifically, the review explores the potential role of various factors, including direct damage to $\beta$-cells, insulin resistance triggered by systemic inflammation, and disturbances in hormonal regulation, aiming to enhance our understanding of the COVID-19 impact on the development and progression of diabetes. By analysing these mechanisms, the aim is to enhance our understanding of the impact of COVID-19 on the development and progression of diabetes. The binding of SARS-CoV-2 to angiotensin-converting enzyme 2 (ACE2) receptors, which are present in key metabolic organs and tissues, may interfere with glucometabolic pathways, leading to hyperglycaemia, and potentially contribute to the development of new disease mechanisms. The virus’s impact on $\beta$-cells through direct invasion or systemic inflammation may induce insulin resistance and disrupt glucose homeostasis. Furthermore, glucocorticoids, commonly used to treat COVID-19, may exacerbate hyperglycaemia and insulin resistance, potentially contributing to new-onset diabetes. The long-term effects of COVID-19 on glucose metabolism are still unknown, necessitating further research into the possibility of developing a novel type of diabetes. This article provides a comprehensive overview of the current understanding of the interaction between COVID-19 and diabetes, highlighting potential areas for future research and therapeutic interventions.

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment by reactivating T cell-mediated anti-tumor immunity. However, this enhanced immune activity can lead to immune-related adverse events (irAEs). This narrative review focuses on endocrine irAEs, including thyroid dysfunction, hypophysitis, adrenal insufficiency, and diabetes mellitus. It also explores infectious complications and their underlying mechanisms. These mechanisms include immune dysregulation resulting directly from ICI-induced T-cell activation and indirectly from the immunosuppressive therapies used to treat irAEs. Furthermore, potential role of endocrine irAEs in predisposing patients to infectious complications is analyzed. The objective is to provide non-oncology specialists with the clinical insight necessary to recognize and manage these complex side effects. This narrative review synthesizes current literature on the diagnosis, management, and pathophysiology of endocrine irAEs and infections associated with different classes of ICIs (anti-CTLA-4, anti-PD-1, and anti-PD-L1). Endocrine irAEs are common, with incidence varying by ICI type; combination therapies pose the highest risk. Thyroid dysfunction is the most frequent, followed by hypophysitis, which often leads to permanent secondary adrenal insufficiency. ICI-induced diabetes mellitus is a rare but serious complication, frequently presenting as diabetic ketoacidosis. ICIs are believed to induce a distinct array of infections resulting from immunological dysregulation, unrelated to immunosuppressive medication. The phenomenon is increasingly called ICI therapy-induced dysregulated immunity. Moreover, evidence suggests that endocrine irAEs can compromise immune function and lead to a significantly higher risk of bacterial and fungal infections. Identifying infections that imitate irAEs is particularly important because the therapy is significantly distinct. Greater interdisciplinary awareness is crucial for the early recognition and appropriate management of both the endocrine and infectious complications, ultimately improving the safety and outcomes for patients receiving immunotherapy.

The helminth infection caused by Strongyloides stercoralis is widespread in tropical regions, but rare in European countries. Unfamiliarity with the disease and diagnostic obstacles could contribute to its lethal outcome. Frequent use of corticosteroids during the COVID-19 pandemic could increase its significance. The aim of this retrospective descriptive study was to explore disease patterns and discuss clinical dilemmas in patients with S. stercoralis hyperinfection treated at the University Hospital for Infectious Diseases ‘Dr. Fran Mihaljević’ in Zagreb, Croatia, between 2010 and 2021. Five out of 22 (22.7%) immunosuppressed patients treated due to strongyloidiasis developed hyperinfection. All patients were male, median 64 years; four were immunosuppressed by corticosteroids (although ileum resection could have been the trigger in one) and one by rituximab. The diagnosis was established after a median of 1.5 months of symptom duration, accidentally in all patients, by visualizing the parasite in the gastric/duodenal mucosa in four cases, and bronchial aspirate in one. All patients were cachectic, four out of five had severe hypoalbuminemia and all suffered secondary bacterial/fungal infection. Despite combined antibiotic, antifungal and antihelmintic therapy, three out of five of the patients died, after failing to clear living parasites from stool samples. We can conclude that significant delays in diagnosis and lack of clinical suspicion were observed among our patients with the most severe clinical presentations of strongyloidiasis. Although being beyond diagnostic recommendations for strongyloidiasis, an early upper gastrointestinal endoscopy with mucosal sample analysis could expedite diagnosis in severe, immunosuppressed patients. The persistence of viable parasites in the stool despite antihelmintic therapy should be further investigated.

Neuroinvasive flaviviruses such as tick-borne encephalitis virus (TBEV) and West Nile virus (WNV) are widely distributed in continental Croatian regions. We analyzed clinical characteristics, laboratory parameters, and molecular epidemiology of neuroinvasive flavivirus infections in eastern Croatia. A total of 43 patients with confirmed flavivirus infection hospitalized from 2017 to 2023 were included in the study. Reverse-transcription polymerase chain reaction (RT-qPCR) was used to detect flavivirus RNA in clinical samples (cerebrospinal fluid; CSF, urine). ELISA was used for IgM and IgG antibody detection in serum and CSF with confirmation of cross-reactive samples by virus neutralization test. WNV was detected more frequently (74.4%) than TBEV (25.6%). A statistically significant age difference was found between WNV patients (median 65 years) and TBEV patients (median 36 years). Comorbidities were more frequently detected in WNV patients (hypertension 56.3 vs. 18.2%; diabetes 31.3 vs. 0%). Meningitis was the most common clinical presentation in both TBE and WNV neuroinvasive disease (WNND; 63.6 and 59.4%, respectively). In addition, some rare clinical presentations of WNND were also detected (cerebellitis, polyradiculoneuritis). No significant differences in the frequency of clinical symptoms were observed between WNV and TBEV-infected patients (fever 93.7 vs. 100%; malaise 78.1 vs. 100%; headache 75.0 vs. 100%; nausea 50.0 vs. 63.6%; vomiting 34.4 vs. 54.6%). Comparative analysis of total and differential leukocyte blood count showed similar results. However, CSF pleocytosis was higher in TBE patients, with a significant difference in the neutrophil and lymphocyte count (WNND median 48.5% and 51.5%; TBE median 10.0 and 90.0%, respectively). The length of hospital stay was 12 days for WNND and 9 days for TBE. Phylogenetic analysis of detected WNV strains revealed the presence of WNV lineage 2 in eastern Croatia.

Acute hyperglycaemia is a common COVID-19 complication linked to adverse outcomes. The combined prognostic value of cytokine activation and acute insulin resistance in non-diabetic patients remains unclear. In this prospective cohort study, we enrolled 144 hospitalised adults with RT-PCR-confirmed SARS-CoV-2 infection and no prior diabetes. We aimed to characterise metabolic–inflammatory phenotypes and evaluate their association with disease severity and post-discharge glycaemic outcomes. Patients were classified as normoglycaemic or dysglycaemic based on repeated glucose profiles. Dysglycaemic patients were further phenotyped as stress hyperglycaemia (SHG) or newly diagnosed diabetes (NOD). This classification was based on post-discharge glycaemic assessment at 3 and 6 months, distinguishing transient from persistent hyperglycaemia. Admission hyperglycaemia was associated with a consistently elevated pro-inflammatory cytokine pattern. However, cytokine concentrations were comparable between stress hyperglycaemia and newly diagnosed diabetes, indicating that inflammatory burden alone does not explain metabolic persistence. In contrast, insulin resistance (HOMA-IR) was markedly higher in the newly diagnosed diabetes phenotype. Along with admission oxygenation and key cytokine signals, this contributed to risk stratification for severe disease. In conclusion, early admission assessment of glucose and insulin resistance identifies high-risk metabolic phenotypes. This enables targeted in-hospital risk stratification and post-discharge glycaemic surveillance.

Sodium imbalance is a common electrolyte disturbance in COVID-19, often linked to disruptions in hormonal regulation. This review explores the relationship between sodium dysregulation and endocrine disturbances, particularly focusing on primary and secondary hypothyroidism, hypocortisolism, and the renin–angiotensin–aldosterone system (RAAS). Hypocortisolism in COVID-19, due to adrenal insufficiency or secondary to pituitary dysfunction, can lead to hyponatremia through inadequate cortisol levels, which impair renal free water excretion and enhance antidiuretic hormone (ADH) secretion. Similarly, hypothyroidism is associated with decreased renal blood flow and the glomerular filtration rate (GFR), which also increases ADH activity, leading to water retention and dilutional hyponatremia. Furthermore, COVID-19 can disrupt RAAS (primarily through its interaction with the angiotensin-converting enzyme 2 (ACE2) receptor), diminishing aldosterone secretion and further contributing to sodium loss and hyponatremia. These hormonal disruptions suggest that sodium imbalance in COVID-19 is multifactorial and warrants further investigation into the complex interplay between COVID-19, endocrine function, and sodium homeostasis. Future research should focus on understanding these mechanisms to develop management algorithms that address both sodium imbalance and underlying hormonal disturbances in order to improve prognosis and outcomes in COVID-19 patients.