25-80% of people with chronic pancreatitis will develop diabetes due to their condition. The specific diabetes is called type 3c diabetes, otherwise known as pancreatogenic diabetes.

What is type 3c diabetes

A healthy pancreas has two functions. The pancreas:

1) controls blood sugar using the hormones insulin and glucagon, and

2) digests food by releasing digestive enzymes

Diabetes is a set of diseases where the first function, blood sugar control, is impaired. Such is the case for type 1 and 2 diabetes.

In contrast, type 3c diabetes causes impairments in both controlling blood sugar and in releasing digestive enzymes, which can make its treatment more difficult. Approximately 1.8% of people with adult-onset diabetes likely have type 3c diabetes due to pancreatitis, but many are misdiagnosed as having type 1, or more frequently, type 2 diabetes. This is problematic, because symptoms and treatment can differ, depending on the type of diabetes a person has. In fact, more people are predicted to have type 3c diabetes than type 1 diabetes, and among hospitalized patients, type 3c diabetes patients comprise up to 9.2% of all diabetes patients. 80% of this type of diabetes is caused by chronic pancreatitis, but other conditions can cause it, too, including pancreatic cancer, the genetic condition cystic fibrosis, and haemochromatosis, a genetic condition where iron accumulates over time and causes damage to various organs.  The risk of type 3c diabetes is higher in those who smoke, pancreatitis patients with a partial pancreatectomy, and increases in people with chronic pancreatitis over time.

Symptoms of type 3c diabetes, and how they compare to those of type 1 and type 2 diabetes

Blood sugar control

In type 1 diabetes, people are typically dependent on injections of the hormone insulin to help regulate blood sugar. In type 2 diabetes, people may initially be able to control their blood sugar with lifestyle changes or medication, but some become insulin-dependent over time. Individuals with type 3c diabetes are likely to need insulin injections to help control their blood sugar. About half of people with diabetes due to chronic pancreatitis are treated with insulin therapy.

People with type 3c diabetes may have mild impairments with blood sugar control, or may have more extreme swings in blood sugar, called brittle diabetes. This latter condition may be due to having impairments in the hormone glucagon or problems with nutrient digestion and absorption, due to pain or nausea from pancreatitis, or alcohol dependence.

Digestive enzyme impairment

Type 3c diabetes impacts the digestive function of the pancreas, causing a condition called exocrine pancreatic insufficiency (EPI) in nearly every person with chronic pancreatitis and diabetes. This can cause symptoms like chronic diarrhea and bloating, and be helped by taking replacement pancreatic enzymes, called PERT [What You Should Know About EPI]. Digestive symptoms due to EPI are less common in other types of diabetes, but do still occur in almost one third of type 2 diabetes patients and one to two thirds of type 1 diabetes patients.

How does pancreatitis cause type 3c diabetes?

Over time in chronic pancreatitis the pancreas loses the ability to produce enough insulin, and thus to control blood sugar. The ability to release enzymes to help digest food also declines in parallel. Scientists don’t yet understand how this happens, but some preliminary research exists. It’s possible that the inflammation from the pancreatitis damages the part of the pancreas that releases insulin, or that the inflammation directly prevents the release of insulin. In later stages of the pancreatitis, the scarring of the pancreas destroys the insulin-producing parts of the pancreas. It is also possible that the body becomes less able to use insulin to regulate blood sugar – called “insulin resistance” – due to chronic pancreatitis over time.

Other causes of diabetes in people with pancreatitis

Rarely, new diabetes in people aged over 50 years turns out to be due to pancreatic cancer. This risk is highest in the first 2-3 years after diagnosis of diabetes. Weight loss at the time of diabetes diagnosis is also more likely in people eventually diagnosed with pancreatic cancer (59%) versus type 2 diabetes (30%). Among all people with new-onset diabetes aged older than 50 (not solely people with pancreatitis), the risk of pancreatic cancer can range from 1% to 13.5%. Nevertheless, the vast majority of people who are diagnosed with new-onset diabetes at those ages solely have diabetes.  It should also be noted that individuals with pancreatitis are still able to get type 1 or type 2 diabetes, independently of their pancreatitis.

References

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Hart PA, Bellin MD, Andersen DK, et al. Type 3c (pancreatogenic) diabetes mellitus secondary to chronic pancreatitis and pancreatic cancer. Lancet Gastroenterol Hepatol. 2016;1(3):226-237.

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Woodmansey C, Mcgovern AP, Mccullough KA, et al. Incidence, Demographics, and Clinical Characteristics of Diabetes of the Exocrine Pancreas (Type 3c): A Retrospective Cohort Study. Diabetes Care. 2017;40(11):1486-1493.