Find the odd one out with respect to the mode of chemical secretion.

Options

A. Pineal gland
B. Pituitary gland
C. Thyroid gland
D. Mammary gland

Answer

To solve the question of finding the odd one out with respect to the mode of chemical secretion among the given options (pineal gland, pituitary gland, thyroid gland, and mammary gland), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Glands**:
- We have four glands: Pineal gland, Pituitary gland, Thyroid gland, and Mammary gland.

2. **Classify the Glands**:
- The first three glands (Pineal, Pituitary, and Thyroid) are classified as **endocrine glands**.
- Endocrine glands secrete hormones directly into the bloodstream, which then travel to target organs to exert their effects.

3. **Understand the Function of Each Gland**:
- **Pineal Gland**: Produces the hormone melatonin, which regulates sleep-wake cycles.
- **Pituitary Gland**: Often referred to as the "master gland," it produces various hormones (like FSH, LH, ACTH) that regulate other endocrine glands.
- **Thyroid Gland**: Produces hormones like T3 (triiodothyronine) and T4 (thyroxine) that regulate metabolism.

4. **Examine the Mammary Gland**:
- The **Mammary Gland** is primarily responsible for the production of milk during lactation. It is not classified as an endocrine gland because it does not secrete hormones into the bloodstream in the same manner as the other three glands. Instead, it produces milk, which is a secretion that is excreted through ducts.

5. **Conclusion**:
- Since the mammary gland is not an endocrine gland and does not primarily secrete hormones into the bloodstream like the other three glands, it is the odd one out.

### Final Answer:
- The correct option is **Mammary Gland** (Option 4).