Amenorrhea means that a woman of childbearing age fails to menstruate. The normal menstrual cycle ranges from 23 to 35 days. It is regulated by the hypothalamus, a portion of the brain that also controls body temperature, appetite and blood pressure. The hypothalamus stimulates the pituitary gland (located near the base of the brain) to release two hormones that regulate female reproductive cycling: luteinizing hormone and follicle-stimulating hormone.
These hormones, in turn, influence production of the hormones estrogen and progesterone, which are responsible for cyclic changes in the lining of the uterus, including menstruation. In order for a woman to have regular menstrual cycles, her hypothalamus, pituitary gland, ovaries and uterus must be functioning properly. Her cervix and vagina must also be anatomically normal to allow the passage of menstrual flow.
Primary amenorrhea is defined as no period by age of 14 in the absence of growth/secondary sexual characteristics or no period by age of 16 regardless of presence of normal growth and development with appearance of secondary sexual characteristics.Primary amenorrhea is most often due to late puberty, which is fairly common in teenage girls who are very thin or very athletic. These young women are typically underweight, and their bodies have not experienced the normal puberty-related rise in body fat that is required to trigger the beginning of menstrual cycling. In other girls, the delay of menses may be due to Turner's syndrome, a genetic disorder involving the sex chromosomes, or to a developmental abnormality of the female reproductive organs.
Secondary amenorrhea is absence of periods for a length of time equivalent to a total of at least three of the previous cycle intervals or six months of amenorrhea.
Secondary amenorrhea can be caused by
Among the general population, amenorrhea currently affects 2 per cent to 5 per cent of all women of childbearing age. Female athletes, especially young women, may be more likely to suffer from amenorrhea. While exercise or physical activity itself does not cause amenorrhea, its likelihood increases with the intensity of exercise, and how quickly a woman increases physical activity. Women who engage in sports associated with lower body weight, such as ballet dancing or gymnastics, are more likely to develop amenorrhea than women in other sports.