About which day in a normal human menstrual cycle does rapid secretion of LH (popularly called LH-surge) normally occurs?

Options

A. 14th day
B. 20th day
C. 5th day
D. 11th day

Answer

To determine the day in a normal human menstrual cycle when the rapid secretion of LH (luteinizing hormone), known as the LH surge, occurs, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Menstrual Cycle**: The menstrual cycle typically lasts about 28 days, though it can vary. It consists of several phases: the follicular phase, ovulation, and the luteal phase.

2. **Identify the Role of LH**: Luteinizing hormone (LH) is produced by the pituitary gland and plays a crucial role in regulating the menstrual cycle. It is secreted at low levels throughout most of the cycle.

3. **Recognize the LH Surge**: The LH surge is a rapid increase in the secretion of LH, which occurs just before ovulation. This surge is critical as it triggers the release of the egg from the ovary.

4. **Timing of Ovulation**: Ovulation typically occurs about 14 days before the next menstrual period starts. Therefore, if we consider a 28-day cycle, ovulation would occur around day 14.

5. **Determine the Day of LH Surge**: The LH surge usually occurs 1 to 2 days before ovulation. Thus, if ovulation is around day 14, the LH surge would occur on day 13 or day 14.

6. **Conclusion**: Based on the above analysis, the rapid secretion of LH (LH surge) normally occurs on day 14 of the menstrual cycle.

### Final Answer:
The LH surge normally occurs on **day 14** of a normal human menstrual cycle.