Estrogen is an important hormone in a woman's reproductive system. It is secreted by the growing follicle at the beginning of each menstrual cycle and plays a variety of roles. The maintenance of normal reproductive function is controlled by the brain, in a region called the hypothalamus. Excessive exercising and weight loss can put the hypothalamus into a "stress" state, whereby normal reproductive function is blocked and a woman fails to have normal estrogen secretion.
The Hypothalamic-Pituitary Axis
A woman's menstrual cycles are regulated by the hypothalamus, a part of the brain. The hypothalamus is important in regulating an individual's emotions, reproductive cycles, movement and energy cycles. The hypothalamus secretes a hormone, gonadotropin releasing hormone, or GnRH. GnRH stimulates the pituitary, another organ in the brain. The pituitary secretes other hormones which stimulate the ovaries with each menstrual cycle. With each cycle, follicles form in the ovaries which produce estrogen. When the egg is released, the ruptured follicles function by producing progesterone. This process continues throughout a woman's reproductive life.
Effects of Exercise
Exercise by itself does not lead to estrogen deficiency, but rather the weight loss that may be associated with it. Gradually increased exercise is less likely to cause estrogen deficiency compared to sudden extreme exercise. The sudden weight loss can cause a stress reaction in the body -- and this may cause a reaction in the hypothalamus to cease menstrual cycles. During these situations, the body responds as if it were in a "starvation state" and the hypothalamus stops secreting GnRH. This is thought to be a protective measure to block reproduction during times of famine or extreme stress. The malfunction of the hypothalamus can lead to a failure of secretion of pituitary hormones that are needed for ovulation and estrogen secretion. The principle sign of this is oligomenorrhea, a decreased frequency of menstrual periods, or amenorrhea, in which menstrual cycles completely stop.
Complications of Amenorrhea
Many women may find the lack of regular menstrual cycles to be a relief; however, it can be associated with a variety of long-term complications. The lack of estrogen can decrease the calcification of bones, predisposing to stress fractures and future osteoporosis. Teenage girls may have decreased growth or a growth arrest. Of course, women who are planning to become pregnant will be unable to if they are unable to have menstrual cycles.
Anorexia Nervosa
The most well known, and serious, disease causing amenorrhea is anorexia nervosa. This is a psychiatric disorder characterized by an abnormal preoccupation with losing weight. According to "Davidson's Principles and Practice of Medicine," this disease is suspected when an individual loses at least 15 percent of their body weight, or has a body mass index of less than 17.5, has amenorrhea for at least three months, excessively avoids high calorie foods, and perceives themselves as fat despite being grossly underweight. Anorexia can have serious consequences, including potentially fatal heart rhythm disorders.
Treatment
Women who stop having their periods following strenuous exercise should consider a variety of lifestyle changes to return to a normal reproductive cycle. Nutritional changes are critical -- women should stop dieting, at least for some time, and focus on having a diet rich in protein. At least 20 percent of dietary calories should come from fat. In addition, women with possible anorexia nervosa should be diagnosed and treated by a psychiatrist to get treated for this dangerous condition.
References
- "Davidson's Principles and Practice of Medicine"; Nicki R. Colledge, et. al; 2010
- Sports MD: Nutrition Tips for Women with Amenorrhea; Nancy Clark MS RD CSSD; February 18, 2011
- USC Fertility: 5 Things You Need to Know About Exercise-Induced Amenorrhea; Dr. Karine Chung
- UpToDate: Amenorrhea and Infertility Associated with Exercise; Michelle P Warren; February 11th, 2011
