While experts have long known that diabetes is a risk factor for more severe illness from COVID infections, many have also suspected an inverse relationship. Earlier this year, microbiologist Peter Jackson of Stanford University published a study in the journal Cell Metabolism showing that SARS-CoV-2 infects pancreatic cells that produce insulin and may even destroy them.

COVID and the Pancreas

The pancreas regulates your blood sugar levels by producing the hormones insulin (which lowers blood sugar) and glucagon (which raises blood sugar). When the two are out of balance, prolonged high blood glucose (hyperglycemia) can cause multiple organ malfunctions and lead to irreversible damage to the heart, kidneys, nerves, retina, and blood vessels.

Paolo Fiorina, an endocrinologist and a professor at the University of Milan, began investigating the effects of COVID on the pancreas in April 2020, after a hospital colleague made a remark concerning how so many COVID patients who had died had also been hyperglycemic. Though diabetes was a known risk factor for severe COVID illness, Fiorina decided to look deeper. In May 2021, he published a study of 551 COVID-19 patients with no history of diabetes and normal hormone levels prior to the infection. Of the 551 patients, 46% were newly hyperglycemic. COVID-19 had completely disrupted their hormone profiles.  

At the same time, researchers–Jackson among them–noticed that autopsies of people who died from COVID-19 also showed that the pancreas had been infected. Subsequent studies found that the virus infects and kills the insulin-producing beta cells. Loss of these cells can increase your risk of developing diabetes.

Questions Remain

It’s not yet clear how SARS-CoV-2 infiltrates the cells of the pancreas. Fiorina’s latest research shows that the virus can be detected in the pancreatic lymph node, suggesting that it may travel either directly through the lymphatic system or through the bloodstream.

Enough time hasn’t passed yet for scientists to fully understand pancreatic outcomes in the months immediately following patients’ recoveries from their infections, but Fiorina’s study found that one-third of those who were newly hyperglycemic retained that status for at least six months after their recovery. He added that even those who don’t have diabetes in the months right after their COVID-19 infection could still develop it in the future. 

To make matters worse, the virus can scar your pancreatic tissue, making you more susceptible to pancreatitis and even pancreatic cancer. “It’s not like having a clean wall that you can put new fresh plaster on,” he said. “Repairing things is harder because you’re starting with a bumpy wall.”

COVID-Pancreas Theory Is Controversial

Despite the appearance of recent evidence, research into a causal relationship between COVID and diabetes is still very new, and not all scientists are on board. This is largely because there are other possible explanations for rising blood sugar levels in COVID patients.

The body’s immune response to COVID-19 can sometimes overreact and cause inflammation across multiple systems. This widespread inflammation can stress the pancreas, increasing blood sugar production. Steroids used by hospitals to treat inflammatory response can also be a factor. 

According to endocrinologist Kathleen Wyne at Ohio State University’s Wexner Medical Center, people with normal hormone profiles and diabetes risk factors have received these steroids without issues. For those already at risk, however, the steroids can cause an overproduction of insulin, driving up patients’ blood sugar. 

Wyne is skeptical about a causal COVID-diabetes connection. Many of her patients at the medical center have been able to stop taking insulin shortly after being discharged. She also claims that, in her experience, new diagnoses of Type 1 diabetes have not increased during the pandemic, and she has seen no evidence of a massive beta-cell die-off.

“I think the real question becomes—what happens when the inflammatory response subsides, what happens when the steroids go away?” Wyne says. “If the diabetes stays there, is that the person who was about to tip over the edge into diabetes anyway?” It’s possible, she says, that for many, the condition is temporary, similar to gestational diabetes during pregnancy. 

New Research May Also Solve Old Mysteries

Scientists have long hypothesized that Type 1 diabetes is caused by an infection, similar to other autoimmune diseases such as Hashimoto’s disease and lupus, but there has never been enough data to prove or disprove this hypothesis. The vast number of coronavirus infections, however, makes collecting the necessary data a distinct possibility.

To facilitate that data collection, Francesco Rubino, chair of metabolic and bariatric surgery at King’s College London, along with several colleagues, started a global registry of patients with COVID-related diabetes. Not only would it help the medical community better understand the dynamics between COVID and the pancreas, he said, but “If you prove with some degree of confidence that COVID can actually cause diabetes, then you have a proof of concept for a viral mechanism behind diabetes.” 

The registry has finally reached more than 620 cases, a large enough sample to begin analyzing the data. Regardless of what they find, however, Rubino warns people infected with the coronavirus that diabetes often progresses undetected until advanced stages that are more complicated to treat. “I think it’s not likely to be a problem for the vast majority of people who had COVID,” he said, “but if you can know earlier rather than later, it’s much better for you.” 

He urges anyone who has recovered from COVID to seek treatment immediately if they experience such early warning signs of diabetes such as fatigue, frequent urination, and unusual, inexplicable thirst.

*McKeever, A. (2021, Oct. 8). COVID-19 is Linked to New Diabetes Cases—But Long-Term Problems Could Be More Severe. National Geographic. https://www.nationalgeographic.com/science/article/the-many-ways-covid-19-seems-to-be-harming-the-pancreas

Much about the novel coronavirus, i.e., COVID-19, is still not fully understood. As research progresses and our knowledge of the virus increases, information can change rapidly. We strive to update all of our articles as quickly as possible, but there may occasionally be some lag between scientific developments and our revisions.