A hormone is :

Options

A. An enzyme
B. Chemical messenger
C. Primary messenger
D. B and C both

Answer

### Step-by-Step Text Solution:

1. **Definition of Hormones**: Hormones are defined as chemical substances secreted by endocrine glands. These glands are ductless, meaning they release hormones directly into the bloodstream rather than through ducts.

2. **Nature of Hormones**: Hormones are classified as non-nutrient chemicals. This means they do not provide nutritional value but serve important regulatory functions in the body.

3. **Function of Hormones**: Hormones act as intercellular messengers, meaning they facilitate communication between cells. They carry signals from one cell to another, influencing various physiological processes.

4. **Production of Hormones**: Hormones are produced in very small amounts (in trace amounts) by the endocrine glands. Despite their low concentration, they have significant effects on target organs.

5. **Types of Messengers**: Hormones can be categorized as primary messengers. They are responsible for delivering messages to target organs. In contrast, secondary messengers (like cyclic AMP and calcium ions) operate within cells to relay the signals initiated by primary messengers.

6. **Conclusion**: Based on the definitions and functions discussed, hormones are not enzymes but are indeed chemical messengers and primary messengers. Therefore, the correct answer to the question is that a hormone is both a chemical messenger and a primary messenger (option B and C).