Patients with CF are living longer than ever before (YES!), but age can bring new health issues--including CFRD. CFRD is very common--50% of CF patients will develop it by age 30. Current guidelines recommend annual oral glucose tolerance tests beginning at age 10.
Insulin secretion defects are present early in CF patients, and are progressive. We know that CFRD doesn't behave exactly like Type 1 or Type 2 diabetes...so what is the mechanism driving the impaired glucose tolerance here? Understanding precisely why so many CF patients develop CFRD could lead to better, earlier therapeutic interventions. After all, CFRD is associated with a lower survival rate and higher rates of lung transplant in CF patients. Not good. Not to mention that CFRD can have a real negative impact on your life. Successfully managing CFRD can be burdensome and time consuming. Symptoms can include decline in BMI and FEV1.
Some readers might be thinking, "My child is young and her sugars are normal--this doesn't apply to me." Dr. Kelly would argue that it DOES. She goes on to explain the typical oral glucose tolerance test (OGTT)--a sugary drink (75 g glucose) is administered, and after 2 hours, the patient's blood is drawn to test blood glucose levels. Levels below 140 mg/dL are considered normal. 140-199 classifies as "glucose sensitive." Levels above 200 mg/dL are diagnostic for CFRD. Dr. Kelly believes that that the standard OGTT may actually miss many CF patients exhibiting early signs of glucose intolerance and goes on to show some evidence. She suggests that CF patients have an initial delayed and blunted insulin secretion, similar to type II diabetics, and believes early indications of this could be picked up more accurately with the non-fasting, 50g glucose test, where blood glucose is tested after 1 hour instead of 2. Her argument is that early insulin abnormalities can be seen in the time immediately after ingesting glucose, and this test could be better at identifying and treating those individuals exhibiting the earliest signs of CFRD. If dealing with CF has taught me anything, it is that it is almost always better to nip problems in the bud before they get big and ugly. Controlling blood sugars is no exception.
She went on to describe how pancreatic enzyme replacement has an effect on insulin secretion. Individuals who take their enzymes properly have improved insulin secretion and blood sugar control! Some of those individuals who screen positive for early glucose intolerance might be able to see some improvement by simply tweaking their enzymes a bit (may need support to be diligent in taking them, others may need a dosage adjustment.) That is nice to know. Others may need alternate interventions.