Level of follicle stimulating hormone (FSH) during infancy and adulthood is the same but spermatogenesis is seen only during adulthood. mRNA levels coding for FSH receptors are also found to be same in testis of both age groups. Which of the following investigations will clarify this paradox a little more?

Options

A. Culture testicular cells and add LH to see testosterone production.
B. Culture testicular cells and add testosterone to see comparative rise in FSH mRNA from both age groups.
C. Culture testicular cells and FSH to see comparative rise in cAMP production by both age groups.
D. Add both LH and FSH to testicular cells and evaluate cAMP production.

Explanation

To clarify the paradox regarding the levels of follicle stimulating hormone (FSH) during infancy and adulthood, and the occurrence of spermatogenesis only during adulthood despite similar mRNA levels for FSH receptors in the testes of both age groups, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of FSH and LH**:
- Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) are crucial for male reproductive function. FSH stimulates Sertoli cells in the testes, while LH stimulates Leydig cells to produce testosterone.

**Hint**: Remember the specific roles of FSH and LH in the male reproductive system.

2. **Recognize the Timing of Spermatogenesis**:
- Spermatogenesis, the process of sperm production, occurs only during adulthood when testosterone levels are sufficient. In infancy, although FSH levels are present, the hormonal environment is not conducive for spermatogenesis.

**Hint**: Consider the importance of testosterone in initiating spermatogenesis.

3. **Investigate the Hormonal Environment**:
- The presence of FSH alone is not enough to trigger spermatogenesis. The action of LH and the resulting testosterone production is also necessary.

**Hint**: Think about what other hormones are required alongside FSH for spermatogenesis to occur.

4. **Evaluate the Investigations**:
- To clarify the paradox, we can culture testicular cells and add LH to see if testosterone production occurs. This would help demonstrate that while FSH levels are similar, the presence of LH and testosterone is critical for spermatogenesis.

**Hint**: Focus on the importance of LH in stimulating testosterone production in the testes.

5. **Select the Correct Investigation**:
- Based on the analysis, the best investigation to clarify the paradox is: "Culture testicular cells and add LH to see testosterone production." This option directly addresses the need for testosterone in the process of spermatogenesis.

**Hint**: Look for options that directly test the relationship between LH and testosterone production.

### Conclusion:
The investigation that will clarify the paradox is to culture testicular cells and add LH to see if testosterone production occurs, as this will highlight the role of testosterone in spermatogenesis, which is not initiated by FSH alone.