Which phenomenon is described by nocturnal hypoglycemia followed by morning hyperglycemia due to a rebound effect?

• A. Somogyi phenomenon.
• B. Dawn phenomenon
• C. HbA1c elevation
• D. Ketone production

Answer: (A)

The pattern described is the Somogyi phenomenon. When blood glucose falls during the night, the body releases counterregulatory hormones such as glucagon, adrenaline, cortisol, and growth hormone. These hormones stimulate hepatic glucose production and limit glucose uptake, causing a rebound rise in the morning that can appear as morning hyperglycemia even if nocturnal insulin was adequate. This rebound effect explains the overnight dip followed by higher fasting glucose.

Dawn phenomenon is a morning rise in glucose due to circadian rhythms and insufficient insulin, but it isn’t triggered by a prior night-time hypoglycemia. HbA1c elevation simply reflects average glucose over the past 2–3 months, not a specific nocturnal–morning pattern. Ketone production relates to fat breakdown and ketosis, not this rebound mechanism. To differentiate, checking nighttime glucose levels (around 2–3 am) helps determine if a nocturnal hypoglycemia event occurred.