Menstruation is a complex process that occurs because of several hormones working together in the body. Certain sex hormones are responsible for changes that affect this process. One of these hormones, known as FSH, is essential for initiating the menstrual cycle. A delicate balance of FSH levels is required for the body to proceed through menstruation.
FSH stands for follicle stimulating hormone, which is a gonadotropin that is secreted by the pituitary gland in the brain 1. Once FSH is secreted, it stimulates the follicles in the ovaries to mature, preparing the body to release an egg. The normal range of follicle stimulating hormone for a woman who is menstruating is between 5 and 20 milli-international units per liter, abbreviated as mIU/L. This level is lowered in women who are pregnant and rises in those who have gone through menopause.
During the early part of the menstrual cycle, when FSH stimulates the ovaries, several follicles increase in size and one will release an egg. This egg travels through the fallopian tubes toward possible fertilization. Simultaneously, the body is preparing the uterine lining for the implantation of a fertilized egg. If fertilization does not occur, the body sheds this lining in the form of blood and tissue during menstruation. After a menstrual period, FSH is secreted again by the pituitary gland to develop another follicle and prepare for a possible pregnancy the following month.
The process of menstruation begins when a girl goes through puberty, a distinct set of changes that moves the body toward adulthood. During puberty, the brain begins to secrete gonadotropin-releasing hormone, a substance that further stimulates the release of follicle stimulating hormone for ovulation. The ovaries produce estrogen, which is responsible for other characteristic changes during puberty, such as breast development and hair growth. FSH is involved in the development of these physical changes, which appear before a girl’s first menstrual cycle.
Because the role of FSH is for the maturation of follicles for pregnancy, it can be used as a method of stimulation for women who are attempting to conceive. Many fertility specialists will give a woman a dose of FSH in the form of an injection to stimulate the process of the menstrual cycle. By doing this, they hope to begin ovulation by stimulating the follicles to produce at least one egg. Instead of letting the body progress through to a menstrual period, they attempt to fertilize the egg, resulting in pregnancy.
Women who are menopausal have FSH levels above 40 mIU/L and will not have menstrual periods. Some women who are younger than 40 years of age and have irregular menstrual cycles or absence of menstruation may have high levels of FSH. These women are said to have premature ovarian failure. This is a process where the body recognizes fewer eggs in the ovaries and increases production of FSH in an attempt to stimulate maturation. This results in higher levels of the hormone in the bloodstream and if an egg matures and is released, menstruation will follow.
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