What hormonal changes occur during the completion of meiosis I in oocytes?

During the completion of meiosis I in oocytes, there is a significant surge in luteinizing hormone (LH). This LH surge is a critical event in the ovarian cycle, triggering ovulation and the final maturation of the oocyte. Prior to ovulation, oocytes are arrested in the prophase of meiosis I, and the LH surge is what leads to the resumption and completion of meiosis I, resulting in the oocyte completing this stage and expelling the first polar body.

The processes involved also include hormonal changes, but the focus here is on the surge of LH. The prominent increase in LH occurs in response to rising estrogen levels produced by developing follicles, signaling that the oocyte is ready for ovulation. This LH surge is essential for the transition from the follicular phase to the luteal phase of the menstrual cycle, subsequently promoting ovulation.

Changes in estrogen, progesterone, and follicle-stimulating hormone (FSH) occur at different stages and do not directly trigger the completion of meiosis I in oocytes as the LH surge does. Therefore, understanding the specific role of LH helps clarify how hormonal signaling regulates oocyte maturation and ovulation.