Following are the functions of a particular hormone:
(a) controller of circadian rhythm in humans
(b) helps in pigmentation, metabolism, menstrual cycle
(C ) controls the defence mechanism of the body
Name the hormone.

Options

A. Epinephrine
B. Gastrin
C. Melatonin
D. Insulin.

Answer

To solve the question regarding the hormone with specific functions, we can break down the information step by step.

### Step 1: Identify the Functions of the Hormone
The question provides three specific functions of a hormone:
1. Controller of circadian rhythm in humans
2. Helps in pigmentation, metabolism, and menstrual cycle
3. Controls the defense mechanism of the body

### Step 2: Analyze Each Function
- **Circadian Rhythm**: This refers to the natural internal process that regulates the sleep-wake cycle and other physiological processes. A hormone that is known to regulate this is melatonin.

- **Pigmentation, Metabolism, and Menstrual Cycle**: Melatonin has been linked to the regulation of the menstrual cycle and can influence metabolic processes. It also plays a role in skin pigmentation.

- **Defense Mechanism**: Melatonin is known to have anti-inflammatory properties and can influence the immune system, thus playing a role in the body's defense mechanisms.

### Step 3: Evaluate the Options
The options given are:
1. Epinephrine
2. Gastrin
3. Melatonin
4. Insulin

- **Epinephrine**: Known as the fight-or-flight hormone, it primarily deals with stress responses and does not regulate circadian rhythms.

- **Gastrin**: This hormone is involved in digestion, specifically in stimulating gastric acid secretion, and does not relate to the functions mentioned.

- **Insulin**: This hormone regulates glucose metabolism and is not involved in circadian rhythms or the defense mechanism.

### Step 4: Conclusion
Based on the analysis of the functions and the evaluation of the options, the hormone that matches all the given functions is **Melatonin**.

### Final Answer
The hormone is **Melatonin**.

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