32 Hypoglycemia
Neonatal hypoglycemia is common, and should be considered in any puppy with nonspecific clinical signs. Hypoglycemia can accompany any neonatal illness that results in anorexia lasting even 24 hours or less. Juvenile hypoglycemia occurs fairly frequently in small-breed dogs younger than 1 year. Hepatic failure and congenital portosystemic shunts can cause hypoglycemia, particularly in young dogs or those with severe hepatocellular dysfunction. Starvation alone is a cause of hypoglycemia by itself only when prolonged (2 weeks or longer), but can contribute to much more rapid development of hypoglycemia in dogs with concurrent illness or preceding cachexia. Sepsis is another relatively common cause of hypoglycemia, and the blood glucose concentration should be measured in any dog that is suspected of having a systemic infection. Exertional hypoglycemia occasionally occurs in dogs after prolonged strenuous exercise; this condition has also been called hunting dog hypoglycemia. Hypoadrenocorticism occasionally causes hypoglycemia to a degree sufficient to cause clinical signs. Hypoglycemia occurs in dogs with hypoadrenocorticism as a result of glucocorticoid deficiency (which may be due to withdrawal of corticosteroids after long-term administration and hypopituitarism), and in these cases, electrolyte abnormalities may be absent. Insulin overdose is a common cause of hypoglycemia in diabetic dogs. Pancreatic islet cell neoplasia (insulinoma) causes severe hypoglycemia due to hypersecretion of insulin. Non–islet cell neoplasia can also cause marked hypoglycemia; hypoglycemia is most likely to be caused by large tumors, such as hepatocellular carcinomas, by splenic neoplasia, or by smooth muscle tumors, particularly of the gastrointestinal tract. Clinicians should avoid diagnosing hypoglycemia based on a single blood glucose measurement in a dog without clinical signs; the diagnosis should always be confirmed by a second fasting blood glucose level.
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