Type 1 diabetes mellitus is a disease in which the body does not produce enough insulin; consequently, the blood glucose is elevated because of the:

• A. Prolonged elevation of stress hormone (cortisol, epinephrine, glucagon, growth hormone) levels.
• B. Malfunction of the glycogen-storing capabilities of the liver.
• C. Destruction of the beta cells in the pancreas.
• D. Insulin resistance of the receptor cells in the muscle tissue.

Answer: (C)

The main idea being tested is that type 1 diabetes causes hyperglycemia because insulin is absent due to destruction of insulin-producing beta cells. Insulin acts to move glucose into muscle and fat cells and to suppress glucose production by the liver. When beta cells are destroyed, insulin levels fall, so glucose can’t enter tissues effectively and the liver continues releasing glucose, driving blood sugar up.

That’s why the destruction of pancreatic beta cells is the best explanation. The other ideas describe ways that glucose can rise in different contexts (stress hormones can raise glucose, hepatic glycogen storage issues aren’t the primary defect in type 1, and insulin resistance is typical of type 2), but they don’t capture the fundamental cause of hyperglycemia in type 1 diabetes.