The hormone insulin is secreted by

Options

A. Hypothalamus
B. Thymus
C. `beta`-cells of islet of Langerhans
D. Pituitary.

Answer

**Step-by-Step Solution:**

1. **Identify the Question:** The question asks about the source of secretion for the hormone insulin.

2. **Review the Options Provided:**
- A) Hypothalamus
- B) Thymus
- C) Beta cells of the islet of Langerhans
- D) Pituitary gland

3. **Analyze Each Option:**
- **Option A: Hypothalamus** - The hypothalamus is located in the forebrain and regulates the secretion of hormones from the pituitary gland. It does not secrete insulin, so this option is incorrect.
- **Option B: Thymus** - The thymus is involved in the immune system's development and is located on the dorsal side of the heart. It does not secrete insulin, making this option incorrect as well.
- **Option C: Beta cells of the islet of Langerhans** - These cells are located in the pancreas and are specifically responsible for the secretion of insulin, which regulates blood glucose levels. This option is correct.
- **Option D: Pituitary gland** - The pituitary gland is known as the master gland because it regulates other endocrine glands, but it does not secrete insulin. Therefore, this option is also incorrect.

4. **Conclusion:** The correct answer is **C) Beta cells of the islet of Langerhans**, as they are the cells responsible for the secretion of insulin.

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