What animal was crucial to the research that identified the cause of diabetes?

• A. Dogs
• B. Rats
• C. Rabbits
• D. Monkeys

Answer: (A)

Diabetes is linked to a deficiency of insulin produced by the pancreas, which normally keeps blood glucose in check. In the landmark work, researchers used dogs in whom the pancreatic duct was tied off, inducing a diabetes-like state. They showed that insulin from the pancreas could treat these diabetic dogs, reversing the symptoms. This established that a pancreatic hormone—insulin—controls blood sugar and that its absence or dysfunction is the root cause of diabetes. Dogs were the primary animal model in that foundational discovery, whereas rats, rabbits, or monkeys contributed to later aspects of diabetes research.