Diabetes mellitus is a disorder which is due to

Options

A. iodine deficiency
B. hormonal deficiency
C. `Na^(+)` deficiency
D. enzyme deficiency

Explanation

### Step-by-Step Text Solution:

1. **Understanding Diabetes Mellitus**:
- Diabetes mellitus is a metabolic disorder characterized by high blood sugar levels over a prolonged period.

2. **Role of the Pancreas**:
- The pancreas is a gland that has both endocrine and exocrine functions. The endocrine part, which is about 1-2% of the pancreas, consists of the islets of Langerhans.

3. **Hormones Produced by the Pancreas**:
- The islets of Langerhans contain two main types of cells:
- **Alpha cells**: These secrete glucagon, a hormone that raises blood glucose levels (hyperglycemic effect).
- **Beta cells**: These secrete insulin, a hormone that lowers blood glucose levels (hypoglycemic effect).

4. **Insulin Deficiency**:
- In diabetes mellitus, there is a deficiency of insulin. This deficiency disrupts the balance between insulin and glucagon, leading to elevated blood glucose levels (hyperglycemia).

5. **Symptoms of Diabetes Mellitus**:
- Common symptoms include excessive hunger (polyphagia), excessive thirst (polydipsia), and excessive urination (polyuria). These symptoms occur because peripheral cells cannot utilize glucose effectively due to the lack of insulin.

6. **Conclusion**:
- Therefore, diabetes mellitus is primarily caused by the deficiency of insulin, which is secreted by the beta cells of the pancreas.

### Final Answer:
Diabetes mellitus is a disorder caused by the deficiency of insulin.

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