Type 1 and 2 diabetes are among the pre-existing conditions associated with more-severe COVID-19 and a greater risk of death from the infection. A growing number of reports have also linked coronavirus infections with new cases of diabetes, prompting researchers to investigate the possibility that SARS-CoV-2 triggers the metabolic disease. 

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To answer some of the questions about how the two diseases influence each other, researchers from King’s College London and Monash University in Australia established the COVIDIAB registry last year to compile detailed reports of COVID-19–related diabetes. According to The Guardian, about 350 clinicians have submitted reports to date.

“The relationship between COVID-19 and diabetes is very complex,” Francesco Rubino, the chair of metabolic and bariatric surgery at King’s College London and one of the researchers who started the registry, tells Scientific American. “It might involve more than one issue.”

A meta-analysis of more than 3,700 patients, published in Diabetes, Obesity and Metabolism in November, found that 14.4% of COVID-19 patients were newly diagnosed with either type 1 or type 2 diabetes. 

“We clearly see people without previous diabetes developing diabetes,” Remi Rabasa-Lhoret, a metabolic diseases researcher at the Montreal Clinical Research Institute, tells CTV News in a March 15 article. “It is highly probable that COVID-19 is triggering the disease.” 

Although other viral infections such as the flu have previously been implicated in new cases of diabetes, “the magnitude of what we see with COVID-19 is above what we’re used to,” says Rabasa-Lhoret.

One of the many questions that researchers have is whether new-onset diabetes is initiated by COVID-19 or if these patients were already at risk of developing the disease. “It’s possible that [a] patient lives with pre-diabetes for many years and didn’t know that,” Mihail Zilbermint, an endocrinologist at Johns Hopkins School of Medicine, tells CTV News. “Now they have COVID-19 infection, and the infection is pushing them towards developing diabetes.”

There are a few possible ways that COVID-19 could trigger diabetes, which is caused either by insufficient insulin, a hormone that regulates cells’ uptake of sugar, or by a reduced sensitivity to insulin. According to Scientific American, SARS-CoV-2 might attack the insulin-producing beta cells of the pancreas or other organs and tissues involved in metabolism. Inflammation related to COVID-19 could also influence blood sugar regulation via stress hormones such as cortisol and adrenaline. It’s also possible that steroids commonly used to treat COVID-19 play a role in diabetes development.