Part One of this series introduced The Female Athlete Triad, a syndrome described by the American College of Sports Medicine (ACSM) in 1992, as the combination of three disorders that can all decrease women’s physical performance and cause morbidity and mortality [1]. The three components are disordered eating, amenorrhea, and osteoporosis, and they are interrelated to each other in their origins, development, and ultimate consequences. The disordered eating usually occurs first, which leads to the menstrual dysfunction, and osteoporosis [2]. This article focuses on amenorrhea and its relationship in The Female Athlete Triad.

Menstrual Cycle Dysfunctions
Amenorrhea, which is a symptom and not a disease, is the absence of menstrual bleeding [1]. It is classified as either primary amenorrhea or secondary amenorrhea. Primary amenorrhea is the absence of menstruation by the age of 16. Secondary amenorrhea is the absence of three or more consecutive menstrual cycles after a woman has already established a menstrual cycle. Amenorrhea that is associated with excessive exercise, disordered eating, or stress is believed to be a type of secondary amenorrhea called functional hypothalamic amenorrhea (FHA) [3]. FHA is a reversible form of amenorrhea that results from psychophysiological and behavioral responses to certain life events that disturb the menstrual cycle.

Menstrual Cycle Mechanics
The menstrual cycle is divided into four phases: the follicular phase, the ovulatory phase, the luteal phase, and the menstrual phase [4]. The duration of the cycle averages 28 days, however it may be as short as 20 days or as long as 45 days. Hormones that come from the hypothalamus, the pituitary gland, and the ovaries fluctuate greatly throughout the cycle. The hypothalamus secretes gonadotropin releasing-hormone (GnRH) in short pulses throughout the cycle. In response to GnRH, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are secreted from the pituitary gland into the ovaries during the follicular phase. These hormones cause growth in the ovarian follicles that contain the egg. Estrogen is secreted from the ovaries during this time to stimulate growth of the endometrium. The ovulatory phase then occurs and large quantities of estrogen and progesterone are secreted to continue endometrial growth. During the luteal phase, the egg is released from the ovary. At the end of the luteal phase, the estrogen and progesterone levels fall and menstruation begins.

Amenorrhea Theories
Amenorrhea was first believed to occur because women who were excessively exercising and dieting had low body weights and body fat [5]. These highly criticized studies stated that all women with body fat percentages below 22% would be subject to amenorrhea. Many studies and reviews since then have shown that a lack of body fat per se does not induce amenorrhea [6]. In addition, most female athletes with normal menstrual cycles have body fat percentages that are below 22% [7].
It is true that the prevalence of menstrual dysfunction is greater among athletes than in the general population [8]. Reports have ranged from 3.4% to 66% in some sports, compared to the reports of 2% to 5% in the general population [2]. But a combination of many factors like weight loss, low body fat, and psychological and exercise stress are all associated with FHA, and scientists are just beginning to sort out all of the details.
FHA results when GnRH secretion from the hypothalamus is decreased. This, in turn, decreases all of the hormones necessary for normal menstruation. The exercise or emotional stress theory suggests that the decrease in GnRH is due to increased levels of cortisol caused by intense exercise and emotional stress [1, 3]. The energy drain theory suggests that GnRH reduction stems from an inadequate calorie intake to match high calorie needs during intense training [9]. Whether one or a combination of these theories proves to cause FHA, it is easy to see how the hypothalamus can be involved. The hypothalamus regulates homeostasis, which is the body’s stable condition, and it controls the autonomic nervous system, the pituitary gland, emotional and behavioral patterns, eating and drinking, body temperature, and sleep cycles [10].

Non-cyclic Consequences
Amenorrhea results in many harmful conditions for the female athlete. The low estrogen levels in amenorrheic athletes are similar to the low levels found in postmenopausal women [2]. These low levels have been associated with a decrease in bone mass which can lead to stress fractures and osteoporosis [11]. Women with amenorrhea may or may not be infertile [12]. This may lead to a false sense of security if they are involved in unprotected sex. Also, hormonal abnormalities can increase the risk for cancer. Fortunately, these harmful effects can be prevented and reversed. The next article in this series will explain the relationship between amenorrhea and osteoporosis.

References
1. Otis, C.L., et al., American College of Sports Medicine position stand. The Female Athlete Triad [see comments]. Med Sci Sports Exerc, 1997. 29(5): p. i-ix.
2. West, R.V., The female athlete. The triad of disordered eating, amenorrhoea and osteoporosis. Sports Med, 1998. 26(2): p. 63-71.
3. Berga, S.L., Stress and ovarian function. Am J Sports Med, 1996. 24(6): p. S36-S37.
4. Guyton, A.C. and J.E. Hall, Textbook of Medical Physiology. Ninth ed. 1996, Philadelphia: W.B. Saunders Company. 1017-1032.
5. Frisch, R.E. and J.W. McArthur, Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset. Science, 1974. 185(4155): p. 949-951.
6. Sanborn, C.F., B.H. Albrecht, and W.W. Wagner, Jr., Athletic amenorrhea: lack of association with body fat. Med Sci Sports Exerc, 1987. 19(3): p. 207-212.
7. De Cree, C., Sex steroid metabolism and menstrual irregularities in the exercising female. A review. Sports Med, 1998. 25(6): p. 369-406.
8. Shangold, M., et al., Evaluation and management of menstrual dysfunction in athletes. Jama, 1990. 263(12): p. 1665-1669.
9. Warren, M.P., The effects of exercise on pubertal progression and reproductive function in girls. J Clin Endocrinol Metab, 1980. 51(5): p. 1150-1157.
10. Tortora, G.J. and S.R. Grabowski, Principles of Anatomy and Physiology. Eighth ed. 1996, New York: HarperCollins. 406.
11. Snow-Harter, C.M., Bone health and prevention of osteoporosis in active and athletic women. Clin Sports Med, 1994. 13(2): p. 389-404.
12. Thein, L.A. and J.M. Thein, The female athlete. Journal of Orthopedic and Sports Physical Therapy, 1996. 23(2): p. 134-148.