Cystic Fibrosis-Related Diabetes

Cystic fibrosis-related diabetes (CFRD) is a unique type of diabetes that is common in people with CF. With early diagnosis and proper treatment, CFRD can be managed successfully.

Causes of CFRD

There are two types of diabetes in people without cystic fibrosis: type 1 and type 2. Type 1 diabetes is an autoimmune disease that occurs when the body's immune system attacks and destroys the cells in the pancreas that make insulin (beta cells), which helps the body absorb and use the energy from food. Type 1 diabetes is most commonly diagnosed in childhood and requires you to take insulin to stay alive.

Type 2 diabetes, which occurs more often in adults who are overweight or obese, is caused by the lack of a normal response to insulin in addition to the pancreas not making enough insulin.

Cystic fibrosis-related diabetes (CFRD) shares some features with both type 1 and type 2 diabetes. In people with CF, the thick, sticky mucus that is characteristic of the disease causes scarring of the pancreas. This scarring prevents the pancreas from producing normal amounts of insulin; so, like people with type 1 diabetes, they become insulin deficient. Their pancreas still makes some insulin, but not enough to stay healthy and maintain good nutrition.

Additionally, people with CFRD may not respond to insulin in the right way like people with type 2 diabetes do, especially when sick, taking steroid medication, or pregnant. This is referred to as being "insulin resistant."

Symptoms, Screening, and Diagnosis

People with CFRD may not experience any symptoms. Some diabetes symptoms are similar to other CF symptoms you may already have. Many people with CFRD do not know they have CFRD until they are tested for diabetes.

Some common symptoms, like increased thirst and urination, are caused by high blood sugar levels, known as hyperglycemia. Other symptoms of CFRD are excessive fatigue, weight loss, and unexplained decline in lung function.

The CF care guidelines for CFRD recommend that people with CF ages 10 and older be tested every year for CFRD with an oral glucose tolerance test (OGTT). The OGTT is the best way to diagnose CFRD and is usually done in the morning after an eight-hour fast. If you are diagnosed with CFRD, you will receive proper treatment in order to feel better, gain weight, and improve your lung function.

It is important to note that OGTT is different than hemoglobin A1c (HbA1c). HbA1c is not recommended as a screening test for CFRD since it is often low in people with CF. This marks another important difference between CFRD and other types of diabetes.

Listen to Andrea Kelly, M.D., talk about CFRD and what's changed since she's been in the field of CF.

Watch this webcast to learn more about CFRD diagnosis and screening.

Treating CFRD

The goal for treating CFRD is to keep blood sugar (glucose) at normal or near-normal levels. Doing so will help you gain weight, maintain muscle mass, feel better, and have more energy. Maintaining normal glucose levels also lowers the risk of problems caused by diabetes.

CFRD can be well managed with insulin, along with monitoring your blood sugar levels, eating your usual high-calorie diet, and staying active.

“Many people with CFRD are unsure about what to eat to manage their blood sugar levels. Fortunately, certain meal planning techniques can help.” -- Gretchen Garlow, MS, RD, LDN, a CF dietitian, from the CF Community Blog

There are many types of insulin, which are grouped by how fast they work and how long they last in the body. Insulin is injected into the body and helps your body cells absorb the energy (calories) from the food you eat. Calories in food come from carbohydrates, protein, and fat. Insulin helps the body cells absorb these three nutrients so that you can achieve and maintain a healthy body weight and good nutritional status.

People with CFRD still need to eat the same high-calorie, high-protein, high-fat, and high-salt diet to help achieve and maintain a healthy body weight. Since foods with carbohydrates turn into blood glucose when eaten, people with CFRD need to count the carbohydrates in the foods they eat so they can give themselves the right amount of insulin. Your diabetes care team will help you determine the amount of insulin you need for your carbohydrates.

Physical activity like exercise is good for lung function and can also improve your body's response to insulin. People with CFRD are encouraged to do at least 150 minutes of some type of moderate aerobic exercise -- activities that require you to breathe in oxygen, like jogging or playing sports -- every week. Monitoring your blood sugar levels will allow you to remain active since exercise may cause the levels to drop when muscles use the sugar for energy.

“If you have CFRD, be sure to check your blood sugar before and after exercise.” -- Lee Degiorgio, an adult with CF, from the CF Community Blog 

If you are diagnosed with CFRD, your CF care team may expand to include an endocrinologist (a doctor with special training in the treatment of diabetes) and certified diabetes educators. Working with you, this team will design a treatment plan to help you manage your diabetes while also maintaining your health with CF.

Download the manual, "Managing Cystic Fibrosis-Related Diabetes, An Instruction Guide for Patients and Families."

The manual is also available in Spanish: "El Manejo de la Diabetes Relacionada con la Fibrosis Quística."

Learn how you can manage CFRD while traveling.

What Research Is Being Done?

The CF Foundation has funded researchers who are investigating the effect that the cystic fibrosis transmembrane conductance regulator (CFTR) protein has on the development of CFRD to find ways to treat it.