Occurrence of Leydig's cells and their secretion is

Options

A. ovary and oestrogen
B. liver and cholesterol
C. pancreas and glucagon
D. testis and testosterone

Explanation

### Step-by-Step Solution:

1. **Identify the Location of Leydig Cells**:
- Leydig cells, also known as interstitial cells, are located in the interstitial spaces between the seminiferous tubules within the testes.

2. **Understand the Function of Leydig Cells**:
- The primary function of Leydig cells is to produce and secrete androgens, with testosterone being the most significant androgen produced.

3. **Hormonal Regulation**:
- The secretion of testosterone by Leydig cells is stimulated by luteinizing hormone (LH), which is secreted by the anterior pituitary gland.

4. **Role of Testosterone**:
- Testosterone plays a crucial role in the development of male secondary sexual characteristics during puberty and is essential for the process of spermatogenesis (the formation of sperm).

5. **Conclusion**:
- Therefore, the occurrence of Leydig cells and their secretion (testosterone) is primarily associated with the testes.

### Final Answer:
The occurrence of Leydig's cells and their secretion is found in the **testes**, where they secrete **testosterone**.

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