The 24 hour (diurnal) rhythm of our body such as the sleep-wake cycle is regulated by the hormone
Or
Which hormone is secreted more in dark condition

Options

A. Insulin
B. Melatonin
C. Thyroxine
D. Adrenaline

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the hormone that regulates the 24-hour (diurnal) rhythm of our body, specifically the sleep-wake cycle, and which hormone is secreted more in dark conditions.

2. **Identifying Key Terms**: The key terms in the question are "24-hour rhythm," "sleep-wake cycle," and "hormone secreted in dark conditions."

3. **Exploring the Options**: The options provided are:
- Insulin
- Melatonin
- Thyroxine
- Adrenaline

4. **Analyzing Each Option**:
- **Insulin**: Secreted by the pancreas, it regulates blood glucose levels and is not directly involved in the sleep-wake cycle.
- **Melatonin**: Secreted by the pineal gland, it is known to regulate sleep patterns and is produced in greater amounts during dark conditions.
- **Thyroxine**: Secreted by the thyroid gland, it regulates metabolism but does not play a significant role in the sleep-wake cycle.
- **Adrenaline**: Secreted by the adrenal glands, it is involved in the fight-or-flight response and does not regulate sleep.

5. **Conclusion**: Based on the analysis, melatonin is the hormone that regulates the sleep-wake cycle and is secreted more in dark conditions. Therefore, the correct answer is **melatonin**.

**Final Answer**: The hormone that regulates the 24-hour rhythm of our body, such as the sleep-wake cycle, is **melatonin**.

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