What is the primary feature of diabetes mellitus?

The primary feature of diabetes mellitus is insulin deficiency or resistance. In this condition, the body either does not produce enough insulin (which is the hormone responsible for regulating blood glucose levels) or the cells become resistant to the effects of insulin. This results in elevated blood glucose levels, which can lead to various symptoms and complications if not properly managed.

Insulin deficiency can occur in Type 1 diabetes, where the body does not produce insulin at all, while insulin resistance is a hallmark of Type 2 diabetes, where the body's cells do not respond effectively to insulin. Both forms of diabetes lead to hyperglycemia, which is the cornerstone of diabetes pathology.

Other options, such as excess insulin production, constant fatigue, and increased sensitivity to cold, do not accurately describe the primary characteristic of diabetes mellitus. For example, while some individuals with diabetes might experience constant fatigue as a symptom due to fluctuating glucose levels, it is not a defining feature of the disorder itself. Similarly, increased sensitivity to cold is not directly related to diabetes but might be associated with other conditions.