Women are increasingly becoming active participants in competitive and recreational physical activity. Concern has arisen regarding the effect of physical training on the physiology of the menstrual cycle. As more women participate and training programs become more strenuous, physicians have seen more complaints of menstrual cycle disturbances.

Clinical effects of exercise training
These patients may present with absence of menses (amenorrhea), thinning of the bones (osteoporosis), irregular menses or intermenstrual bleeding, abnormal growth of the uterine lining or infertility. The nature and severity of the symptoms seen are dependent on a number of variables such as the specific type of training, the intensity and duration of training, weekly mileage, and rate of progression of training program.

Normal menstrual cycle
During the first half of the normal menstrual cycle the pituitary gland at the base of the brain stimulates development of an egg (follicular development) and estrogen production by the ovarian. After release of the egg (ovulation), the ovary produces progesterone to ready the uterine lining for implantation of the early fertilized egg. The portion of the menstrual cycle after ovulation is called the luteal phase and normally lasts two weeks. Normal pituitary function is controlled by another part of the brain, the hypothalamus.

We call this interdependent relationship between the brain and the ovaries the hypothalamic-pituitary-ovarian axis (HPO for short) The hypothalmus is affected by variables such as associated nutrition and dietary factors (caloric, fat, or weight restrictions), menstrual pattern prior to onset of training, age when training began. These factors determine ability of the HPO-axis to withstand the further stress brought on by exercise.

Progressive nature of menstrual disturbances.

1. Regular cycles with shortened luteal phase-progesterone production stops early
2. Regular cycles with Inadequate progesterone production
3. Regular cycles with failure to develop and release an egg (anovulation)
4. Irregular cycles but still ovulating
5. Irregular cycles and anovulation
6. Absence of menses and ovulation

Usually stages 1-3 are asymptomatic but may present as infertility.

Research study results:

1. Low to moderate exercise (15-20 miles/week) begun in sedentary women with regular cycles and > one year buildup will not result in problems. Moderate to intense training (30-50 miles/week) building up over two months in young women will more than likely result in significant menstrual abnormalities.

    

2. Even recreational joggers at 12-18 miles /week demonstrated poor follicular development, decreased estrogen and progesterone secretion and absent ovulation.

    

3. One out of four moderate and long distance runners demonstrated one or more episode of anovulation when observed for one year.

Prevalence:
Studies reveal exercise induced amenorrhea in 1 to 44% of athletes. Most frequently seen in ballet dancers and long distance runners. Up to 44% of ballet dancers have been found to be amenorrheic.

Theories:
Pathophysiologic mechanisms responsible for exercise induced amenorrhea are not well understood.

critical fat hypothesis: During puberty menses first occurs when body fat content rises beyond 17% and menses will cease if it subsequently falls below 12%. However, menses will resume in amenorrheic ballet dancers after injury in the absence of any significant change in weight or body fat. Amenorrhea returns when their training resumes.

energy drain: Low caloric input and high caloric expenditure results in endocrine abnormalities manifest as menstrual disturbances. Studies have found decreased caloric intake and a lower metabolic rate in amenorrheic athletes compared to those with normal menses. However, some have postulate that the lower resting metabolic rate is just the body's adaptive response in attempt to maintain weight and conserve energy thereby restoring a more normal energy balance.

eating disorders: Eating disorders such as anorexia and bulimia have been seen in athletes. These conditions have been associated with amenorrhea. In these patients nutritional and psychological factors must be considered.

physical & psychological stress: associated changes seen in several neurohormones such as dopamine and opioids (the body's own "morphine-like" painkillers, may relate to exercise addiction or joggers high) have been shown to interfere with normal hypothalamic function. b-endorphin, one of the opioids, is known to be elevated in the circulation immediately after exercise. It has also been noted to be chronically elevated at rest in competitive swimmers who have trained for two or more years. Psychological stress as seen with strenuous exercise training is associated with an increase in cortisol (an adrenal stress hormone). In the amenorrheic athlete, the adrenal gland may be secreting cortisol at near maximum levels even at rest! The cause of excessive cortisol secretion or how it affects hypothalamic function are as yet unknown.

Clinical implications of exercise-induced menstrual abnormalities:
As menstrual abnormalities may be caused by medical conditions not related to exercise, it is important that an appropriate medical evaluation be made.

Infertility:
Patients with infertility may demonstrate decreased estrogen & progesterone production, poor follicular development and anovulation. Menstrual cycles and hormone production may frequently return to normal upon assuming a less strenuous training schedule and insuring adequate caloric intake. Frequently ovulation inducing medications are necessary to achieve pregnancy. These include clomiphene (the fertility pill), pergonal (a daily injection) or a new device called the GnRH Pump (lutrepulse system) which appears to offer many advantages to the athlete with amenorrhea. By closely mimicking the normal hypothalamic hormone production, the pump can safely & effectively restore normal fertility. As infertility may be related to factors other than ovulation and normal menstrual function, a thorough evaluation should be completed. this includes looking at the semen analysis in the male and evaluating the female for cervical mucus problems or blocked fallopian tubes.

Osteoporosis:
The hormone changes seen with exercise, diminished levels of estrogen and progesterone and the increased levels of circulating cortisol result in decreased bone mineral density. This may even be seen in patients with normal menstrual cycles. As calcium is lost, the bones become more brittle and spinal compression fractures can occur.

Peak bone mass is achieved by age 35. Bone mass gradually decreases from that time onward and more rapidly decreases after the menopause. This loss of bone is referred to as osteoporosis. It is a devastating condition that can result in hip fracture, spinal fractures, debility and death in elderly women.

Estrogen replacement and calcium supplementation during the menopause are effective at slowing bone loss. One great concern is that the decreased estrogen levels and avoidance of dairy products frequently seen in women with moderate or strenuous training, a normal peak bone mass may never be reached. This is of particular concern in the patient with absent menses. These patients are at much greater risk for osteoporosis and bone fractures while young. This can usually be prevented by hormone replacement to restore normal estrogen levels.