What Is Cystic Fibrosis-Related Diabetes (CFRD)?

Cystic fibrosis–related diabetes (CFRD) is a complication of cystic fibrosis (CF). CF is an inherited disorder that causes the mucus in your body to be thick and sticky. It affects many organs and body systems, including your pancreas.

If your pancreas becomes too damaged, it will be difficult to make enough of the hormone insulin to take the sugar out of your bloodstream. If this happens, you will develop diabetes.

This article will discuss the symptoms of CFRD, how it's diagnosed and treated, and how CFRD affects people living with cystic fibrosis.

How CFRD Develops

A mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene causes CF. This gene makes a protein that helps the mucus around your organs and tissues stay thin and move freely around your body. It also helps your lungs, digestive system, and pancreas function properly. The mutation causes mucus to become thick and sticky. CFRD is one of the major complications of CF due to damage to the pancreas from this mucus.

The American Diabetes Association (ADA) has classified CFRD is as type 3c diabetes mellitus (T3cDM). This type of diabetes is caused by a disease of the pancreas. Symptoms, diagnosis, and management of T3cDM are different from those for type 1 diabetes (your body makes little to no insulin) and type 2 diabetes (the insulin made in your body does not work properly).

Symptoms of CFRD

CFRD often shows no symptoms at first. There may be episodes of hyperglycemia (high blood sugar) during lung infections or treatment with corticosteroids. Other symptoms of diabetes, like excessive thirst and increased urination, might be confused as CF symptoms.

Additional signs to look out for include:

• Feeling more tired than usual
• Weight loss or inability to maintain weight
• In children, poor growth or delay of puberty
• More lung exacerbations (flare-ups)

Diagnosing CFRD

Because CFRD often shows no symptoms, routine screening will help get an early diagnosis. The ADA and the Cystic Fibrosis Foundation recommend using the two-hour 75 gram oral glucose tolerance test (OGTT) to diagnose CFRD. CF patients 10 years and older should get screened annually.

The criteria for diabetes diagnosis will be different for people with CF. Blood sugar levels considered prediabetic in the general population may be considered normal in those with CF.

CFRD diagnostic criteria if your CF is stable include:

• Two-hour OGTT blood sugar of 200 milligrams per deciliter (mg/dL) or more
• Fasting blood sugar (which measures your blood sugar after a night of not eating) of 126 mg/dL or more
• A1C (a blood test used to diagnose diabetes and prediabetes) of 6.5% or more
• Standard symptoms of diabetes (excessive urination or thirst) with blood sugar levels of 200 mg/dL or more

CFRD diagnostic criteria during a CF flare-up or corticosteroid treatment include:

• Fasting blood sugar of 126 mg/dL or more
• Blood sugar levels of 200 mg/dL or more two hours after a meal for more than 48 hours

CFRD Treatment

Oral diabetes medication is not currently recommended for CFRD patients. Insulin therapy is the most effective treatment. This will include taking rapid-acting insulin before meals. For patients with hyperglycemia in between meals, a combination of rapid-acting and slow-acting basal insulin may be used.

Current guidelines for blood sugar level goals if you have CFRD include:

• Fasting blood sugar between 70 and 130 mg/dL
• Below 180 mg/dL two hours after a meal

With CFRD, an illness may cause temporary insulin resistance. You will need higher doses to control your blood sugar until the illness clears up.

Outlook

CFRD is a lifelong condition and does not have a cure. CF patients with diabetes are more likely to experience poor lung function and, eventually, lung failure. However, treatments for CF and CFRD have vastly improved in recent years. Now people with CF are living longer than ever before.

But CFRD can be successfully managed with insulin therapy, especially when diagnosed early. Health outcomes have been greatly improved with the recommendation for annual screenings for diabetes in patients with CF.

Summary

Cystic fibrosis–related diabetes (CFRD) is a complication of cystic fibrosis (CF). CF is caused by a genetic mutation that makes the body's normally thin mucus thick and sticky. This mutation damages organ systems, particularly the lungs and pancreas. CFRD develops when the pancreas cannot make enough insulin to remove the sugar from your blood.

For patients with CF, guidelines for diagnosing diabetes are a bit different than for types 1 or 2 diabetes. One instance of high blood sugar may not result in a CFRD diagnosis. The recommendation is to screen CF patients annually. Symptoms are much the same as when someone develops type 1 or type 2 diabetes. However, you may not experience any symptoms at all.

CFRD is managed with insulin therapy. Health outcomes have improved significantly due to the recommendation for annual screenings. It is important to get an early diagnosis to decrease the risk of lung failure.

A Word From Verywell

A CFRD diagnosis can feel overwhelming. You are faced with the challenge of managing two chronic conditions at the same time. But the good news is that medical research has made it possible to manage CFRD successfully. Insulin therapy is proven to keep blood sugar in control for people with CFRD.

For the best chance of success, follow the treatment plan that your healthcare provider has created for you. This means taking prescribed medication as directed, eating a healthy diet, and getting regular exercise. Always consult with your healthcare provider if you have questions or concerns.