What causes amenorrhea?
The normal menstrual cycle occurs because of changing levels of hormones made and secreted by the ovaries. The ovaries respond to hormonal signals from the pituitary gland located at the brain's base, which, in turn, is controlled by hormones produced in the hypothalamus of the brain. Disorders that affect any component of this regulatory cycle can lead to amenorrhea. However, a common cause of amenorrhea in young females sometimes overlooked or misunderstood by the individual and others, is an undiagnosed pregnancy. Amenorrhea in pregnancy is a normal physiological function. Occasionally, the same underlying problem can cause or contribute to either primary or secondary amenorrhea. For example, hypothalamic problems, anorexia or extreme exercise can play a major role in causing amenorrhea depending on the person's age and if she has experienced menarche.
Primary amenorrhea is typically the result of a genetic or anatomic condition in young females that never develop menstrual periods (by age 16) and is not pregnant. Many genetic conditions that are characterized by amenorrhea are circumstances in which some or all of the normal internal female organs either fail to form normally during fetal development or fail to function properly. Diseases of the pituitary gland and hypothalamus (a region of the brain important for the control of hormone production) can also cause primary amenorrhea since these areas play a critical role in the regulation of ovarian hormones.
Gonadal dysgenesis, a condition in which the ovaries are prematurely depleted of follicles and oocytes (egg cells), leads to premature failure of the ovaries. It is one of the most common cases of primary amenorrhea in young women.
Another genetic cause is Turner syndrome, in which women are lacking all or part of one of the two X chromosomes normally present in the female. In Turner syndrome, the ovaries are replaced by scar tissue and estrogen production is minimal, resulting in amenorrhea. Estrogen-induced maturation of the external female genitalia and sex characteristics also fails to occur in Turner syndrome.
Other conditions that may be causes of primary amenorrhea include androgen insensitivity (in which individuals have XY (male) chromosomes but do not develop the external characteristics of males due to a lack of response to testosterone and its effects), congenital adrenal hyperplasia, and polycystic ovary syndrome (PCOS).
Pregnancy is an obvious cause of amenorrhea and is the most common reason for secondary amenorrhea. Further causes are varied and may include conditions that affect the ovaries, uterus, hypothalamus, or pituitary gland.
Hypothalamic amenorrhea is due to a disruption in the regulator hormones produced by the hypothalamus in the brain. These hormones influence the pituitary gland, which in turn sends signals to the ovaries to produce the characteristic cyclic hormones. A number of conditions can affect the hypothalamus:
Other types of medical conditions can cause secondary amenorrhea:
- tumors or other diseases of the pituitary gland that lead to elevated levels of the hormone prolactin (which is involved in milk production) also cause amenorrhea due to the elevated prolactin levels;
- elevated levels of androgens (male hormones), either from outside sources or from disorders that cause the body to produce too high levels of male hormones;
- ovarian failure (premature ovarian failure or early menopause);
- polycystic ovary syndrome (PCOS); and
- Asherman's syndrome, a uterine disease that results from scarring of the uterine lining following instrumentation (such as dilation and curettage) of the uterine cavity to manage postpartum bleeding or infection.
Women who have stopped taking oral contraceptive pills should experience the return of menstruation within three months after discontinuing pill use. Previously, it was believed that birth control pills increased a woman's risk of amenorrhea following use of the pill, but this has been proven not to be the case. Women who do not resume menstruation after three months have passed since oral contraceptive pills were stopped should be evaluated for causes of secondary amenorrhea.