Diabetes mellitus is defined as a disease in which blood glucose levels are too high due to the inability of insulin to channel glucose into cells.

• A. Diabetes mellitus
• B. Hyperthyroidism
• C. Endocrinologist
• D. Hypothyroidism

Answer: (A)

This question tests recognizing what defines diabetes mellitus as a disease of glucose regulation. Diabetes mellitus is characterized by high blood glucose because insulin cannot effectively move glucose from the blood into body cells that need it for energy. This happens when there is not enough insulin (as in type 1) or when the body's cells don’t respond properly to insulin (as in type 2), leading to hyperglycemia over time.

The other options are different conditions: hyperthyroidism and hypothyroidism involve thyroid hormones affecting metabolism, not the primary problem of glucose uptake into cells. An endocrinologist is a clinician who treats hormone disorders, not the disease itself.