Select the correct statement.

Options

A. Pineal gland secretes melatonin
B. Vasopressin is secreted by kidneys
C. Endocrine system of invertebrates is very complex
D. `T_3` is secreted from follicular cells of parathyroid glands

Answer

To solve the question, we need to analyze each of the four statements provided and determine which one is correct.

### Step-by-Step Solution:

1. **Evaluate Statement 1: "Pineal gland secretes melatonin."**
- The pineal gland is located on the dorsal side of the forebrain and is known for secreting the hormone melatonin. Melatonin is crucial for regulating sleep-wake cycles and maintaining circadian rhythms.
- **Conclusion:** This statement is correct.

2. **Evaluate Statement 2: "Vasopressin is secreted by kidney."**
- Vasopressin, also known as Antidiuretic Hormone (ADH), is produced in the hypothalamus and secreted by the posterior pituitary gland. It acts on the kidneys to regulate water balance but is not secreted by the kidneys themselves.
- **Conclusion:** This statement is incorrect.

3. **Evaluate Statement 3: "Endocrine System of Invertebrates is very complex."**
- The endocrine system of invertebrates is generally considered to be simpler than that of vertebrates. Invertebrates have fewer hormones and simpler regulatory mechanisms.
- **Conclusion:** This statement is incorrect.

4. **Evaluate Statement 4: "T3 is secreted from follicular cells of parathyroid gland."**
- T3, or triiodothyronine, is a thyroid hormone that is produced in the thyroid gland, specifically from the follicular cells. The parathyroid glands are responsible for secreting parathyroid hormone (PTH), which regulates calcium levels in the blood.
- **Conclusion:** This statement is incorrect.

### Final Conclusion:
- The only correct statement is **Statement 1: "Pineal gland secretes melatonin."**