In women, the menstrual cycle is a self-regulating process during which the body undergoes many physiological and hormonal changes. The menstrual cycle is regulated by two hormones secreted by the pituitary gland: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These hormones control the production of the estrogen and progesterone hormones that are produced in the ovaries. 
Women begin their menstrual cycle during puberty, at the beginning they begin with menarche, which is the first menstruation. At this time, girls can have irregular menstruation, this being totally normal. Women will continue to have menstrual cycles throughout their fertile lives until they reach menopause, which occurs between the ages of 40 and 60.
The time in which women’s period comes down
- The average menstrual cycle lasts approximately 28 days, but it can last between 24 and 42 days, all being regular periods if women always have more or less the same days. When women have irregular cycles, menstruation can go months without appearing, being in some women something completely normal when it is always like this and in others when they have regular menstrual cycles and suddenly there are problems with their periods, you will have to find out with the help of the doctor what is exactly what is happening.
- A woman’s menstrual cycle has three phases: the menstrual phase, the follicular phase, and the luteal or secretory phase. These three phases are the ones that mark the menstrual rhythm of each woman.
- The menstrual phase. The menstrual phase is when the lining of the uterus, called the endometrium, sheds as menstrual fluid out of the cervix and vagina. This is the rule, where the menstrual flow consists of blood, mucus and tissues. The first day of menstrual flow is defined as day one of the next menstrual cycle. Menstruation lasts approximately 3 to 7 days (although it can be shorter or longer). Menstruation indicates that the woman is not pregnant, however, the woman can become pregnant in menstruation, since she can conceive at any time of her menstrual cycle.
- The follicular phase. This phase (also known as the proliferative phase) is when the follicles in the ovaries develop and mature to prepare for ovulation. Only one ovule will reach full growth, which will be the one that will be released during menstriation. In this phase the ovaries produce estrogen. The egg is then released and will travel to the fallopian tubes. The release of the mature egg is called ovulation and occurs 14 days before the start of the next menstrual period and will be when the woman is at her most fertile in her menstrual cycle.
- The secretory or luteal phase. After ovulation, estrogen and progesterone are at their highest levels because they help prepare the endometrium to secrete nutrients that feed the embryo if a fertilized egg were to implant. If conception and implantation do not occur, the pituitary gland will reduce the production of hormones, the corpus luteum deteriorates and the endometrium will be shed, causing the next period and the menstrual cycle again.
