Ovulation is associated with sudden rise in –

**Core Concept**
Ovulation is a critical phase in the menstrual cycle where a mature ovum is released from the ovary, making it available for fertilization. This process is regulated by a complex interplay of hormones and neural signals.

**Why the Correct Answer is Right**
During ovulation, there is a significant surge in the levels of luteinizing hormone (LH), which triggers the release of the ovum from the antral follicle. This LH surge is mediated by the hypothalamic-pituitary-gonadal axis, specifically through the action of gonadotropin-releasing hormone (GnRH) on the anterior pituitary gland. The resulting LH surge stimulates the ovary to release the ovum into the fallopian tube.

**Why Each Wrong Option is Incorrect**
**Option A:** While estrogen levels do increase during the follicular phase, the sudden rise associated with ovulation is primarily due to LH, not estrogen.
**Option B:** Progesterone levels rise after ovulation, but this is a consequence of ovulation, not the cause.
**Option C:** Testosterone is a sex hormone produced by the ovaries and testes, but it is not directly involved in the ovulation process.

**Clinical Pearl / High-Yield Fact**
The LH surge is often used as a marker for ovulation, and its timing can be used to determine the optimal window for conception.

**Correct Answer:** D. Luteinizing hormone (LH)