**Core Concept**
GnRH (Gonadotropin-releasing hormone) analogues are synthetic peptides that mimic the action of natural GnRH, initially stimulating and eventually downregulating the pituitary gland's production of gonadotropins (LH and FSH). This leads to a decrease in sex hormone production, making them useful in various clinical scenarios.

**Why the Correct Answer is Right**
GnRH analogues are used in the treatment of hormone-sensitive cancers, such as prostate cancer and breast cancer, to reduce tumor growth by decreasing sex hormone levels. They are also used in conditions like endometriosis, uterine fibroids, and precocious puberty to suppress sex hormone production. Additionally, GnRH analogues are used in assisted reproduction to induce ovulation and improve sperm quality.

**Why Each Wrong Option is Incorrect**
**Option A:** GnRH analogues are not typically used for the treatment of thyroid disorders, making this option incorrect.
**Option B:** GnRH analogues are not primarily used for the treatment of hypertension, although they may have a secondary effect on blood pressure. This option is somewhat related to the correct use but is not the best answer choice.
**Option C:** GnRH analogues are not typically used for the treatment of type 2 diabetes, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
GnRH analogues can cause an initial flare effect due to the initial stimulation of gonadotropin production, which can worsen symptoms in conditions like prostate cancer. This effect is temporary and resolves once the downregulation of GnRH receptors occurs.

**Correct Answer:** D.