The Somogyi Effect is Rare in Diabetic Cats Managed Using Glargine and a Protocol Aimed at Tight Glycemic Control
The Somogyi effect is defined as hyperglycemia caused by the release of counter-regulatory hormones in response to insulin-induced hypoglycemia, and it is widely believed to exist in diabetic cats. However, studies in human diabetic patients over the last quarter century have rejected the common occurrence of the Somogyi phenomenon. The aim of this study was to determine the frequency of the Somogyi effect in diabetic cats treated with glargine.
Fifty-five cats diagnosed with diabetes mellitus were included in the study. Data were collected over 20 months, and were obtained from owners who joined the online German Diabetes-Katzen Forum, and followed a protocol of intensive blood glucose regulation using glargine. The aim was to achieve euglycemia (50-100 mg/dL as measured using a portable blood glucose monitor) using twice daily insulin dosing. Owners performed an average of 5 ± 2 blood glucose measurements per day, and supplied spreadsheets recording all blood glucose concentrations.
The Somogyi effect was defined differently in cats that had good glycemic control compared to those that were not well controlled. For cats that were well controlled and had their nadir concentrations in the normal range (50-80 mg/dL) on an almost daily basis for >2 weeks, a Somogyi effect was defined as a glucose concentration of <40 mg/dL, followed by a fast, steep rise in blood glucose concentration to >400 mg/dL, and/or concentrations that were at least 150 mg/dL above the usually measured higher concentrations. The two subsequent insulin doses showed almost no effect, and the glucose concentration remained elevated for >24 hours. In cats that had never had a glucose concentration in the normal range or only had nadir glucose concentrations in the normal range for several days, a Somogyi was defined as a blood glucose concentration of <70 mg/dL, followed by a fast, steep rise in glucose concentration to >400 mg/dL and/or concentrations that were at least 200 mg/dL above the usually measured higher concentrations for that cat. The two subsequent insulin doses showed almost no glucose lowering effect, and the glucose concentrations remained elevated for >24 hours.
Asymptotic or biochemical hypoglycemia was common and most cats (93%) had blood glucose concentrations > 40 to <50 mg/dL measured at some point during the study, 84% had glucose concentrations > 30 to <40 mg/dL, and 51% had some glucose concentrations > 20 to <30 mg/dL.
Although biochemical hypoglycemia was common, the Somogyi effect was very rare in this cohort of diabetic cats. Based on the criteria, only 4 single events were identified in 4 different cats.
We conclude that that the Somogyi effect is rare in cats treated with glargine on a protocol aimed at tight glycemic control, despite the frequent occurrence of biochemical hypoglycemia.