Cystic Fibrosis-Related Diabetes (CFRD) is a unique form of diabetes that affects individuals with cystic fibrosis (CF). It is a common extrapulmonary complication for people with CF, impacting organs outside the lungs. Early detection and management of CFRD are important because it can influence overall health, including lung function and nutritional status in individuals with CF.
Understanding CF-Related Diabetes
CFRD is a distinct type of diabetes linked to cystic fibrosis, a genetic condition. It is one of the most common complications in adults with CF, with prevalence increasing with age. For instance, it affects approximately 2% of children with CF, rises to about 19% in adolescents, and can impact up to 50% of individuals aged 30 and older.
CFRD shares characteristics with both Type 1 and Type 2 diabetes but has its own unique features. Similar to Type 1 diabetes, individuals with CFRD experience insulin deficiency. CFRD is not an autoimmune condition, distinguishing it from Type 1 diabetes. Like Type 2 diabetes, individuals with CFRD can also develop insulin resistance. Unlike typical Type 2 diabetes, CFRD patients are generally not obese and do not exhibit the full metabolic syndrome features.
How CFRD Develops
The development of CFRD is rooted in the effects of cystic fibrosis on the pancreas. CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which leads to the production of thick, sticky mucus throughout the body. In the pancreas, this thick mucus can block ducts, causing chronic inflammation and scarring. This damage can impair the insulin-producing beta cells, reducing insulin secretion.
Pancreatic dysfunction in CF extends to insulin production, contributing to insulin deficiency. Chronic inflammation and infections can also contribute to insulin resistance, further complicating glucose regulation. Certain medications, such as steroids used to treat CF, can also induce insulin resistance.
Recognizing and Diagnosing CFRD
Recognizing CFRD can be challenging because its symptoms often overlap with those of cystic fibrosis itself. Individuals with CFRD may experience increased thirst, frequent urination, excessive fatigue, unexplained weight changes, and a decline in lung function. Increased exacerbations and infections are also possible. Many people with CFRD may not notice any symptoms, emphasizing the importance of regular screening.
Due to the often subtle presentation, annual screening for CFRD is recommended for individuals with CF aged 10 years and older. The primary diagnostic tool is the oral glucose tolerance test (OGTT). This test involves measuring blood glucose levels after an overnight fast, then administering a glucose drink, and taking subsequent blood samples at 1 and 2 hours to assess how the body processes sugar. A diagnosis of CFRD is made if the 2-hour plasma glucose level is 200 mg/dL or higher. Other criteria, such as a fasting plasma glucose of 126 mg/dL or higher, or a random glucose level of 200 mg/dL or higher in a symptomatic individual, also indicate CFRD.
Treatment and Management Strategies
The primary treatment for CFRD is insulin therapy, to maintain near-normal blood glucose levels. Insulin is typically administered via injections multiple times a day or through an insulin pump, a device delivering insulin continuously. Oral diabetes medications are generally not as effective as insulin for CFRD and are rarely recommended.
Nutritional considerations are a significant aspect of CFRD management. Individuals with CFRD should maintain a high-calorie, high-protein diet as recommended for CF patients, while balancing carbohydrate intake to manage blood glucose. Adequate hydration and vitamin and mineral supplementation are part of a comprehensive nutritional plan.
Regular monitoring of blood glucose levels is important, often multiple times daily using a blood glucose meter or a continuous glucose monitor (CGM). Monitoring helps guide insulin adjustments and assess glycemic control. Quarterly monitoring of HbA1c levels is recommended to assess average blood glucose over time.