Hypoglycemic seizures in a Shetland pony.

The research article discusses an unusual case of hypoglycemic seizures in a Shetland pony, linked to a pancreatic neoplasm and excessive insulin production.

Case Presentation and Diagnosis

• The study centers around a 12-year-old Shetland pony broodmare which had experienced eight seizures between May and August of 1979. Anomalies were noticed in plasma glucose and serum insulin levels during these seizures.
• Three seizures showed significantly low plasma glucose levels (16, 18, and 19 mg/100 ml) while during two others, the serum insulin levels were exceptionally high (86.0 and 97.7 microU/ml).
• Although the mare did not show fasting hypoglycemia, plasma glucose levels assessed throughout a typical day were abnormal. A notably low plasma glucose level was recorded eight hours post-feeding.

Evaluation of Insulin and Glucose Levels

• Serum insulin levels measured during an oral glucose tolerance test and intravenous glucagon tolerance test revealed consistent signs of organic hyperinsulinism of a pancreatic origin. This refers to an elevated insulin level in the body due to causes within the pancreas.
• In an attempt to distinguish the subject pony from control ponies, a twenty-four hour fast and an intravenous glucose tolerance test were conducted. These tests, however, failed to mark a clear difference between the subject and control ponies concerning plasma glucose and serum insulin levels.

Pathological Findings

• A pathological examination of the pancreas found a single adenoma (a benign tumor) of pancreatic islet cell origin around 2.0 mm in size, along with the hyperplasia (increase in the number) of islet cells, mainly beta cells which produce insulin.
• The investigation concludes that the hypoglycemic seizures in the mare were due to this pancreatic neoplasm and its associated hyperinsulinism.
• This study is significant as it is the first documented instance of a horse experiencing hypoglycemic seizures as a result of a pancreatic tumor and excessive insulin production.