**Core Concept**
GnRH analogues are used in the hormonal treatment of carcinoma of the prostate to suppress testosterone production, which is essential for the growth and proliferation of prostate cancer cells. This principle is based on the concept of androgen deprivation therapy (ADT), which aims to reduce the levels of androgens such as testosterone in the body.

**Why the Correct Answer is Right**
GnRH analogues work by initially stimulating the pituitary gland to release GnRH, which in turn stimulates the secretion of LH and FSH from the pituitary gland. However, with continuous administration of GnRH analogues, the pituitary gland becomes desensitized, leading to a decrease in LH and FSH secretion. This decrease in LH and FSH results in a decrease in testosterone production by the testes. The most commonly used GnRH analogue in the treatment of prostate cancer is leuprolide.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a GnRH analogue commonly used in the treatment of prostate cancer. While it may be used for other indications, it is not the preferred choice for prostate cancer treatment.
**Option B:** This option is incorrect because it is not a GnRH analogue at all. It is a different class of medication used for a different indication.
**Option C:** This option is incorrect because, although it is a GnRH analogue, it is not the most commonly used one in the treatment of prostate cancer.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that GnRH analogues can cause an initial flare effect, which can worsen symptoms in patients with prostate cancer. Therefore, it's crucial to initiate these medications with a GnRH antagonist or a non-steroidal anti-androgen to prevent this flare effect.

**Correct Answer: C. Leuprolide**