MKSAP Quiz: Type 1 diabetic with morning symptoms
This month's quiz asks readers to evaluate a 33-year-old woman for a 3-week history of fatigue, excessive sweating, and occasional headache on awakening.
A 33-year-old woman is evaluated for a 3-week history of fatigue, excessive sweating, and occasional headache on awakening. The patient has had type 1 diabetes mellitus since age 18 years. Her blood glucose log for the past 2 weeks shows fasting blood glucose levels ranging between 125 and 146 mg/dL (6.9 to 8.1 mmol/L) (average, 135 mg/dL [7.5 mmol/L]) and an average predinner level of 176 mg/dL (9.8 mmol/L). She does not check her level at other times during the day but occasionally experiences hypoglycemic symptoms around lunchtime, especially if she does not eat enough. She lives alone and usually exercises 1 hour each evening. Her diabetes regimen is premixed 70/30 insulin (neutral protamine Hagedorn [NPH] insulin/regular insulin) before breakfast and before dinner.
Physical examination shows a slim but well-appearing woman. Temperature is 36.6 °C (97.9 °F), blood pressure is 104/63 mm Hg, pulse rate is 66/min, and respiration rate is 14/min; BMI is 18. Other physical examination findings are unremarkable. Results of laboratory studies show a hemoglobin A1c value of 5.7% (estimated average plasma glucose level, 120 mg/dL [6.7 mmol/L]).
Which of the following is the most likely cause of her symptoms?
A. Dawn phenomenon
B. Nocturnal hypoglycemia
C. Sleep apnea
D. Somogyi phenomenon
MKSAP Answer and Critique
The correct answer is B. Nocturnal hypoglycemia. This item is available to MKSAP 16 subscribers as item 31 in the Endocrinology section. Information about MKSAP 16 is available online.
This patient's symptoms are most likely caused by nocturnal hypoglycemia. Her hemoglobin A1c value is lower than what her blood glucose log averages suggest. Frequent episodes of significant hypoglycemia for several hours each night would explain this discrepancy. The 70/30 insulin she takes twice daily gives a single large peak 6 to 8 hours after taking it. This patient exercises every evening, which means that her muscles will continue to remove glucose from her blood to replenish their glycogen stores for several hours afterward. This occurrence could cause her blood glucose to decrease to very low levels while she sleeps. Given the duration of her diabetes mellitus, the appropriate adrenergic counterregulatory response may be adequately blunted to not cause her to awaken from sleep but can lead to fatigue, sweating, and headache when she awakens.
The dawn phenomenon is defined as an elevation in blood glucose levels during the early morning hours (4 a.m. to 8 a.m.) that is thought to be related to the increased physiologic release of cortisol and growth hormone that occur during this time period. The dawn phenomenon is typically identified by persistent significant elevations of morning blood glucose levels, which were not seen in this patient.
Although sleep apnea may be a cause of fatigue and early morning headache, it is more often seen in obese patients with type 2 diabetes who have an associated high hemoglobin A1c value.
The “Somogyi phenomenon” is a phrase used to describe the theoretical concept that the lower the blood glucose level decreases during the night, the higher it increases the next morning because of increasingly severe rebound hyperglycemia. This idea, however attractive on a theoretical level, has been disproven as a cause of fasting hyperglycemia.
Key Point
- Frequent nocturnal hypoglycemia may cause morning fatigue, sweating, and headache in patients with type 1 diabetes mellitus.