Rebound hyperglycaemia in diabetic cats

Abstract

Objectives: Rebound hyperglycaemia (also termed Somogyi effect) is defined as hyperglycaemia caused by the release of counter-regulatory hormones in response to insulin-induced hypoglycaemia, and is widely believed to be common in diabetic cats. However, studies in human diabetic patients over the past quarter century have rejected the common occurrence of this phenomenon. Therefore, we evaluated the occurrence and prevalence of rebound hyperglycaemia in diabetic cats.

Methods: In a retrospective study, 10,767 blood glucose curves of 55 cats treated with glargine using an intensive blood glucose regulation protocol with a median of five blood glucose measurements per day were evaluated for evidence of rebound hyperglycaemic events, defined in two different ways (with and without an insulin resistance component).

Results: While biochemical hypoglycaemia occurred frequently, blood glucose curves consistent with rebound hyperglycaemia with insulin resistance was confined to four single events in four different cats. In 14/55 cats (25%), a median of 1.5% (range 0.32-7.7%) of blood glucose curves were consistent with rebound hyperglycaemia without an insulin resistance component; this represented 0.42% of blood glucose curves in both affected and unaffected cats.

Conclusions and relevance: We conclude that despite the frequent occurrence of biochemical hypoglycaemia, rebound hyperglycaemia is rare in cats treated with glargine on a protocol aimed at tight glycaemic control. For glargine-treated cats, insulin dose should not be reduced when there is hyperglycaemia in the absence of biochemical or clinical evidence of hypoglycaemia.

Figure 1

(a) Boxplots comparing maximum blood glucose concentrations occurring after the nadir between days when the nadir was ⩽50 mg/dl (⩽2.8 mmol/l) and days when the nadir was >50 mg/dl to ⩽100 mg/dl (>2.8 mmol/l to ⩽5.5 mg/dl) in cats not yet regulated (mean blood glucose >200 mg/dl [11 mmol/l]). (b) For days when blood glucose was ⩾300 mg/dl (⩾16.7 mmol/l) following a nadir, a similar comparison of maximum blood glucose concentrations after a nadir was made between days when the nadir was in the normal range (>50 mg/dl to ⩽100 mg/dl [>2.8 mmol/l to ⩽5.5 mg/dl]) or below normal (⩽50 mg/dl [⩽2.8 mmol/l]; consistent with rebound hyperglycaemia)

Figure 2

A histogram with a normal curve, showing the first insulin dose (IU) given to each of the 14 cats which produced a curve that was consistent with rebound hyperglycaemia