At a follow-up visit, Rachel's blood glucose records indicate that her levels have been consistently high when she wakes in the morning before breakfast. Describe the dawn phenomenon. Is Rachel experiencing this? How might it be prevented?

Question

What will be an ideal response?

Answer 1

The dawn phenomenon is the tendency for blood glucose to rise between 4 am and 8 am. This is fairly common for T1DM and over 55% of patients are likely to experience the dawn phenomenon. This occurs because of impaired insulin sensitivity in muscle and liver cells from nocturnal secretion of growth hormone due to circadian rhythms. This increases the production of glucose and hyperglycemia results. Also, poor glucose control is related to high and more frequent changes to blood glucose levels. Patients experiencing the dawn phenomenon have an increase of blood glucose >10 mg/dL or an increased insulin requirement of 20% during these hours of the night.
Because Rachel's blood glucose is dropping low and then is running high by the morning, she is not experiencing the dawn phenomenon, but rather "rebound." Rebound also results in high fasting blood glucose, but for a different reason. Along with Rachel treating the 2 am hypoglycemia with 15 grams of carbohydrates orally, her body is naturally treating the hypoglycemia by the increased secretion of counter-regulatory hormones, such as glucagon, epinephrine, and growth hormone/cortisol. These increase gluconeogenesis from lipids and proteins, causing more glucose to be secreted into the blood, further raising Rachel's blood glucose. To prevent this from happening, Rachel should check her blood sugar before going to bed, as well as in the middle of the night. She can also decrease her evening insulin dosage or increase the amount of carbohydrates in her bedtime snack. Either of these steps will keep hypoglycemia from occurring and avoid the promotion of glucose production by counter-regulatory hormones.