The menstrual cycle is guided by a carefully timed rise and fall of hormones, mainly estrogen and progesterone, along with follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

At the start of the cycle (menstruation), hormone levels are at their lowest, which triggers the shedding of the uterine lining.

As the follicular phase begins, FSH stimulates the growth of ovarian follicles, and estrogen gradually rises. This boost in estrogen not only helps the uterine lining rebuild but also gives many people an increase in energy, mental clarity, and even brighter moods.

Around the middle of the cycle, estrogen peaks and a sharp surge in LH triggers ovulation - the release of a mature egg.

After ovulation, progesterone levels rise during the luteal phase, working to prepare the uterus for a possible pregnancy. Progesterone tends to have a calming effect, but if pregnancy doesn’t occur, both estrogen and progesterone levels drop toward the end of the cycle. This hormonal dip is what often brings on premenstrual symptoms such as mood changes, bloating, and fatigue, before the cycle begins again with menstruation.