Progestin - estradiol combined contraceptive pills inhibit ovulation by

Options

A. negative feed back on the release of estrogen from ovary required for follicular development
B. prventing the uterine physiological and morphologica changes required for implanttion
C. inhibiting the secretion of FSH and LH
D. both 1 & 3

Answer

To answer the question regarding how progestin-estradiol combined contraceptive pills inhibit ovulation, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Role of FSH and LH**:
- Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) are critical hormones in the menstrual cycle. FSH is responsible for stimulating the growth of ovarian follicles, while LH triggers ovulation.

2. **Mechanism of Combined Contraceptive Pills**:
- Progestin-estradiol combined contraceptive pills work primarily by inhibiting the secretion of FSH and LH from the anterior pituitary gland. This inhibition prevents the normal hormonal signals that would lead to follicular development and ovulation.

3. **Negative Feedback Mechanism**:
- The presence of synthetic hormones (progestin and estradiol) in the bloodstream creates a negative feedback loop that signals the pituitary gland to reduce the production of FSH and LH. This is crucial because lower levels of these hormones mean that the ovarian follicles do not mature and ovulation does not occur.

4. **Additional Effects**:
- Besides inhibiting FSH and LH, these pills also induce physiological changes in the endometrium (the lining of the uterus), making it less suitable for implantation. However, the primary mechanism for inhibiting ovulation is through the suppression of FSH and LH.

5. **Conclusion**:
- Therefore, the correct answer to the question is that progestin-estradiol combined contraceptive pills inhibit ovulation by inhibiting the secretion of FSH and LH (Option C).

### Final Answer:
Progestin-estradiol combined contraceptive pills inhibit ovulation by inhibiting the secretion of FSH and LH.

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