What are the two main types of diabetes mellitus?

The two main types of diabetes mellitus are Type 1 and Type 2. Type 1 diabetes is an autoimmune condition where the body's immune system attacks and destroys the insulin-producing beta cells in the pancreas. This typically leads to a complete lack of insulin, requiring individuals with Type 1 diabetes to rely on external sources of insulin for management. It often manifests in childhood or early adulthood.

On the other hand, Type 2 diabetes is characterized by insulin resistance, where the body's cells do not respond effectively to insulin, often coupled with a progressive decline in insulin production over time. Type 2 diabetes is more commonly associated with lifestyle factors such as obesity, physical inactivity, and poor diet, and it generally develops in adults, though increasing cases are seen in children and adolescents.

The other choices are not accurate representations of the main types of diabetes. Type 3, although sometimes referred to in discussions about diabetes, does not represent a formally recognized category in the context of diabetes classifications. Similarly, the designation Type A and Type B is not a standard classification for diabetes mellitus, as the focus remains primarily on Type 1 and Type 2 for clinical and medical purposes.