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Hypoglycaemia is a common, life-threatening complication that occurs as a component of a wide variety of disease processes. Despite its frequent occurrence, information concerning the aetiology, characteristics and outcomes of hypoglycaemic crises in veterinary medicine is limited. This review summarises the current understanding of the pathophysiology of hypoglycaemia, the body's counter-regulatory response, underlying aetiologies, diagnosis and treatment. Disease mechanisms are discussed and published evidence in veterinary literature regarding prognostic indicators, prevalence, diagnosis and treatment is examined for hypoglycaemia-related disease processes including insulinoma, glucose-lowering toxins and medications., (© 2018 British Small Animal Veterinary Association.)

Objectives: Hypoglycaemia is a common cause of morbidity in dogs with congenital portosystemic shunts but the aetiology is unknown. The hypothesis of this study was that dogs with congenital portosystemic shunts would have significantly higher insulin concentrations than dogs without congenital portosystemic shunts. The main objective of the study was to compare peripheral glucose and insulin concentrations between dogs with congenital portosystemic shunts and dogs without congenital portosystemic shunts., Methods: Peripheral serum insulin and plasma glucose concentrations were measured in dogs with congenital portosystemic shunts and without congenital portosystemic shunts and compared both between groups as well as to reference intervals derived from healthy dogs., Results: Congenital portosystemic shunts were diagnosed in 41 dogs. Forty-eight dogs hospitalised with other conditions acted as controls. Serum insulin concentrations were mildly elevated (Ä40 μU/mL) in seven dogs and were markedly elevated in two dogs with congenital portosystemic shunts, yet mild hypoglycaemia (3·3 mmol/L) was detected in only one of these dogs. Four dogs with congenital portosystemic shunts showed fasting hypoglycaemia, yet insulin concentrations were within or below the reference interval in three. There was no difference between the median insulin concentration of dogs with congenital portosystemic shunts and without congenital portosystemic shunts., Clinical Significance: Hyperinsulinaemia is infrequently observed in dogs with congenital portosystemic shunts. The aetiology of hypoglycaemia in dogs with congenital portosystemic shunts merits further investigation., (© 2012 British Small Animal Veterinary Association.)

A 14-year-old domestic shorthair cat was presented with hypoglycaemia and seizures of several weeks duration. Bloodwork revealed hypoglycaemia (1.83 mmol/l; reference range 4.22-8.05 mmol/l) with concurrent normal insulin levels (171 pmol/l; reference range 72-583 pmol/l). An insulinoma was suspected and medical and dietary management were attempted with minimal success. An exploratory laparotomy was performed and a single, well-defined mass was found within the left lobe of the pancreas. The mass was removed and histologically classified as an islet cell carcinoma, consistent with an insulinoma. The cat had an episode of presumed postoperative pancreatitits, but recovered with appropriate treatment. The cat has had no clinical signs of recurrence of greater than 32 months postsurgery. There are only four cases of insulinoma in cats reported in the literature. All prior insulionomas reported were in older cats and were malignant in character, which is similar to the reports in the dog. This case is unique because of the apparent lack of local recurrence and development of metastatic disease, leading to the prolonged survival.

Hypoglycaemia was accompanied by sinus bradycardia and circulatory collapse in a dog and a cat. In each case, when the hypoglycaemia was corrected by intravenous infusion of a glucose solution the bradycardia and circulatory failure were soon abolished, indicating that these abnormalities were caused by the hypoglycaemia. Similar observations have been made in human patients. To the author's knowledge, this is the first report documenting hypoglycaemic bradycardia in veterinary medicine.

A six-year-old neutered female pointer was referred for evaluation of seizures that occurred only in association with exercise. A tenacious ocular discharge was also evident and tear production was decreased bilaterally. Diagnostic testing revealed severe hypoglycaemia caused by secondary hypoadrenocorticism. Treatment was instituted with prednisone (5 mg, orally, once daily) and the seizures ceased. Tear production returned to normal without additional treatment. Glucocorticoid deficiency should be considered a cause of hypoglycaemic seizures once other, more common, causes have been ruled out.

Simultaneous insulin and glucose measurements from a single sample are often insufficient for the laboratory diagnosis of insulinoma in the hypoglycaemic dog. Although the simple insulin (microU/litre): glucose (mmol/litre) ratio is best, when the selected threshold is set at 13.5, it is not always efficient to confirm or refute insulinoma. The fasting test consists of collecting four samples on a given day (no accurate time period is set between any two samples) from a fasting dog for simultaneous insulin and glucose measurements to detect at least one abnormal insulinaemia peak.

A five-year-old intact male rottweiler was presented with a history of episodic weakness and mild-generalised seizures. A tentative diagnosis of an insulin-secreting tumour in the pancreas was made based on fasting hypoglycaemia with concomitant hyperinsulinaemia and a subnormal fructosamine value. The diagnosis was confirmed by exploratory coeliotomy, intravenous infusion of methylene blue, histopathology and immuno-histochemical analysis of suspected neoplastic tissue. Fructosamine assays are traditionally used for monitoring the metabolic status of diabetics where a single elevated measurement reflects persistent hyperglycaemia. This report suggests that a single low measurement of fructosamine may indicate persistent hypoglycaemia and may be helpful, in conjunction with an insulin measurement, in the diagnosis of insulin-secreting tumours.

The response of dogs with insulinoma to surgical and medical management is variable, with the majority developing intractable hypoglycaemia. A long-acting somatostatin analogue, Octreotide (SMS 201-995; Sandostatin) has been useful in the management of hypoglycaemia in humans with insulinoma, and preliminary reports suggest a beneficial clinical response in dogs with insulinoma. The present study objectively evaluated Octreotide in the management of three dogs with immunohistochemically confirmed insulinoma. Octreotide had no benefit over placebo, and little effect on circulating glucose and insulin concentrations despite clearly detectable plasma concentrations of Octreotide. No clinical improvement was apparent in two dogs given Octreotide over a period of two and three weeks. These results contrast with the positive clinical responses noted previously and indicate that further placebo controlled, objective studies are necessary before clear statements on the treatment of insulinoma with Octreotide are made.