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
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?
Women runners with a history amenorrhea and oligomenorrhea have increased
stress fracture risk:
From Barrow and Saha, 1988.
Bone density is significantly lower in amenorrheic athletes than in
Bone mineral density of amenorrheic (gray bars) and normally-menstruating
athletes (black bars). Asterisk indicates statistically significant difference.
From Rencken et al., 1996.
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.
What is involved?
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
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.
Who is Eligible?
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
Treated athletes will be provided with oral contraceptive therapy at no
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
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
Participants cannot already be taking oral contraceptives or have taken
them within the previous six months.
If you have questions, please contact:
Kristin Cobb, Project Director
Katrina Mogielnicki, Associate Director
Division of Epidemiology
Department of Health Research and Policy
HRP Redwood Building
Stanford, CA 94305
Toll Free: 1-877-RUN-BFIT
Study Investigative Team:
Jennifer Kelsey, Ph.D., Stanford University
Laura Bachrach, M.D., Stanford University
Robert Neer, M.D., Massachusettes General Hospital
MaryFran Sowers, Ph.D., University of Michigan
Gail Greendale, M.D., UCLA
Byron Brown, Ph.D., Stanford University
Kristin Cobb, Stanford University
Katrina Mogielnicki, Stanford University
This health study is made possible by funding from the
US Army Medical Research and Material Command.