Which of the following is a disorder of the endocrine system?

Diabetes Mellitus is a disorder of the endocrine system because it directly involves the malfunctioning of the pancreas, which is responsible for producing insulin, a critical hormone that regulates blood sugar levels. In Diabetes Mellitus, either the body does not produce enough insulin (as in Type 1 diabetes) or the cells become resistant to insulin (as in Type 2 diabetes), leading to elevated glucose levels in the bloodstream. This hormonal imbalance impacts various bodily functions and requires careful management, which is a fundamental aspect of endocrine disorders.

In contrast, Alzheimer's Disease is a neurodegenerative disorder primarily affecting the brain; seizures are a neurological condition, and fractures are physical injuries to bones. These options do not relate to the hormonal regulation and hormone-producing glands that characterize endocrine system disorders.