Background

• Many competitive women athletes experience menstrual irregularities.
• Menstrual irregularities include amenorrhea (the absence of a menstrual period) and oligomenorrhea (infrequent menstruation). Athletes may also experience hidden abnormalities such as shortened luteal phase, and anovulatory cycles.
• Menstrual irregularities reflect low serum estrogen levels.
• Estrogen is a key hormone in bone deposition and maintenance.
• Women athletes with menstrual irregularities are at increased risk for low bone mass and stress fractures.

What are the Risks?

• Stress Fractures

Women runners with a history amenorrhea and oligomenorrhea have increased stress fracture risk:

From Barrow and Saha, 1988.
• Osteopenia

Bone density is significantly lower in amenorrheic athletes than in normally-menstruating controls:

Bone mineral density of amenorrheic (gray bars) and normally-menstruating athletes (black bars). Asterisk indicates statistically significant difference. From Rencken et al., 1996.
 
 
• Premature Osteoporosis

Some women with athletically-induced amenorrhea have bone densities that would be typical for elderly women:

Spine bone mineral density (BMD) is plotted against a normative data base. The cross in the right panel illustrates the bone density of a 28-year-old competitive female runner. Subject was having normal menstrual cycles at the time of the bone scan but had an 8-year history of exercise-associated amenorrhea. Her spine bone density (0.874 g/cm2) is nearly equivalent to that of a 69-year-old woman (0.877 g/ cm2), illustrated in the left panel. The older woman's spine density is average for her age, but the runner's spine density is well below the average value for her age.
From Snow-Harter, 1994.

• Oral contraceptives contain estrogen and regulate the menstrual cycle.
• Estrogen replacement has been shown to prevent bone loss in post-menopasual women and in pre-menopausal women with medical conditions such as premature ovarian failure and hyperprolactinemia.
• It is unknown if estrogen replacement prevents bone loss in women athletes with menstrual irregularities, as the hypothesis has never been tested.

• This study is a randomized trial of oral contraceptive use in 150 female cross country runners.
• The study will test the hypothesis that oral contraceptives reduce stress fracture incidence and prevent loss of bone mass or increase bone mass among highly trained female athletes.
• This study is important because it is the first trial to test the efficacy of oral contraceptives as a bone health intervention among women athletes.

• Each participant will remain in the study for two years.
• Eligible participants will be randomly assigned to the treatment (oral contraceptive) group or to the control group, and will be informed of their assignment and supplied with oral contraceptives if assigned to the treatment group..
• All participants will have their bone density and body fat percentage measured by dual x-ray absorptiometry.
• Participants will be asked to respond to questionnaires on diet, menstrual and reproductive history, injury history, and training.
• Participants will be asked to return monthly menstrual calendars that record the length and timing of their menstrual cycle.
• Participants will be monitored for stress fractures throughout the course of the study.

• All participants will have their whole body, spine, and hip bone densities and their body fat percentages measured. This is an expensive test, but will be paid for by the study, including transportation to the testing site.
• Treated athletes will be provided with oral contraceptive therapy at no cost.
• Any athlete who suspects she has a stress fracture will be able to get a bone scan; the study will cover all costs not covered by the student's insurance.
• Most importantly, your participation will help further our knowledge about bone health in women runners and will help future women athletes.

• Participants must be women, 18-25 years of age, who are on an intercollegiate cross country team or who run competitively, approximately 40 miles per week.
• Participants cannot already be taking oral contraceptives or have taken them within the previous six months.