**Core Concept**
Medical castration, also known as chemical castration, refers to the use of medications to reduce or eliminate sex hormone production, particularly testosterone in males. This is achieved through the inhibition of the hypothalamic-pituitary-gonadal (HPG) axis.

**Why the Correct Answer is Right**
LH-RH (Luteinizing Hormone-Releasing Hormone) analogues work by mimicking the action of natural LH-RH, leading to an initial surge in LH and FSH secretion. However, as the body adapts, the LH-RH analogues are internalized, reducing LH and FSH secretion, which in turn decreases testosterone production. This results in a decrease in sex drive and fertility. The mechanism involves the downregulation of LH-RH receptors in the pituitary gland, leading to a decrease in LH and FSH secretion.

**Why Each Wrong Option is Incorrect**
**Option A:** Diethylstilbestrol (DES) is a synthetic estrogen used for various purposes, including the treatment of prostate cancer. However, it is not typically used for medical castration due to its estrogenic effects and potential for causing gynecomastia.

**Option C:** Gossypol is a toxic compound found in cottonseed oil that has been investigated as a potential male contraceptive. However, it has not been widely adopted due to its toxicity and potential side effects.

**Option D:** HCG (Human Chorionic Gonadotropin) is a hormone that can stimulate testosterone production. It is used in some cases to treat hypogonadism and infertility, but it is not used for medical castration.

**Clinical Pearl / High-Yield Fact**
When using LH-RH analogues for medical castration, it is essential to note that the initial surge in LH and FSH secretion can cause an increase in testosterone levels, which may worsen symptoms in patients with prostate cancer.

**Correct Answer:** B. LH RH analogues