## **Core Concept**
The question tests understanding of pharmacological agents used in the management of infertility, specifically those that induce ovulation. Antihormonal substances or more accurately, anti-estrogenic agents, play a role in this process. Clomiphene citrate is a key drug in this category.

## **Why the Correct Answer is Right**
Clomiphene citrate works by competitively inhibiting estrogen receptors in the hypothalamus. This inhibition disrupts the normal feedback mechanism by which estrogen levels regulate the release of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). As a result, the hypothalamus perceives a lower estrogen level and responds by increasing GnRH secretion, which in turn stimulates the pituitary gland to release more LH and FSH. This increase in LH and FSH stimulates follicular growth and ovulation. Clomiphene citrate is a **mixed estrogen receptor agonist/antagonist**, with predominantly anti-estrogenic effects in the hypothalamus.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain progestins can influence the menstrual cycle and are used in fertility treatments, they are not primarily used to induce ovulation through antihormonal (anti-estrogenic) action.
- **Option B:** This option might seem plausible due to its role in fertility treatments, but it does not accurately represent clomiphene citrate or its mechanism.
- **Option D:** Without a specific agent listed, it's hard to directly refute, but generally, GnRH analogs can be used to induce ovulation but work through a different mechanism, directly stimulating GnRH receptors.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that clomiphene citrate is often the first-line treatment for inducing ovulation in women with polycystic ovary syndrome (PCOS) or other causes of anovulatory infertility. Its use is associated with an increased risk of multiple gestations.

## **Correct Answer:** C. Clomiphene citrate