December 6, 2021
The menstrual cycle is a series of changes that occur naturally and repeatedly in the female reproductive system, especially the ovaries and uterus, which allow pregnancy to occur. The menstrual cycle includes the ovarian cycle and uterine cycle. The ovarian cycle regulates the production and release of eggs and the regular release of estrogen and progesterone, while the uterine cycle regulates the preparation and maintenance of the uterine lining to receive a fertilized egg as a site for pregnancy. These two cycles occur simultaneously and are coordinated, usually lasting 21–35 days in adult females with a median value of 28 days, and lasting for about 30–45 years. These cycles are driven by hormones that the body produces naturally. Gonadotropin-releasing hormone (GnRH) stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH plays a major role in the initiation of ovarian follicular growth, while LH plays a major role in follicular development. Meanwhile, the hormones estrogen and progesterone stimulate the uterine lining to thicken to accommodate the embryo as a result of fertilization. The endometrium (the lining of the uterus where the embryo is implanted) will thicken and provide a suitable environment for the embryo, including a blood supply that carries nutrients. If implantation of the embryo does not occur, the lining of the uterus breaks down so that the blood can no longer be accommodated and is released. Menstruation (menstruation), which is triggered by a drop in progesterone levels, is a process of shedding the lining of the uterus and a sign that pregnancy is not occurring. Each cycle has several phases based on events in the ovaries (ovary cycle) or uterus (uterine cycle). The ovarian cycle consists of the follicular, ovulatory, and luteal phases, while the uterine cycle consists of the menstrual, proliferative, and secretory phases. At around the fourteenth day, the egg is usually released from the ovary. Menarche (first menstruation) usually occurs at the age of 12 years. The menstrual cycle can cause some women to experience disturbances in their daily lives. They can experience menstrual pain, tenderness of the breasts, fatigue, and premenstrual syndrome (PMS). More severe problems such as premenstrual dysphoric disorder can occur in 3–8% of women. The use of hormonal contraceptives can affect the menstrual cycle.