Diabetes mellitus is characterized by which of the following?

Diabetes mellitus is indeed characterized as a chronic disease of insulin deficiency. This condition arises primarily due to the body's inability to produce adequate amounts of insulin (as seen in Type 1 diabetes) or the body's resistance to insulin (as seen in Type 2 diabetes). Insulin is a crucial hormone that regulates blood glucose levels by facilitating the uptake of glucose into the cells for energy. When insulin levels are insufficient or ineffective, glucose accumulates in the bloodstream, leading to the hallmark symptoms and complications associated with diabetes.

The other choices do not accurately represent the characteristics of diabetes mellitus. A temporary decrease in sugar levels, an increase in cortisol production, and a reduction in hemoglobin levels do not directly relate to the fundamental aspects of diabetes. Instead, they describe other physiological changes or conditions that may occur in different contexts but are not defining features of diabetes mellitus.