How Does the Menstrual Cycle Influence Bone Health?

In athletics, stories of success often overshadow the struggles that lurk beneath the surface. Take Mary Cain, a promising athlete who rose through the ranks in 2013 to join Nike’s prestigious Oregon Project, considered the world’s premier track team at the time. Behind the facade of success, there was a troubling reality. After restrictive dieting and pressure from her coach, Mary Cain shared with the New York Times that she lost her menstrual period for three years and broke five bones.

Her experience underscores a common pitfall in striving for peak performance. We often focus on visible signs of progress, like muscle growth or speed, while overlooking more elusive players in our health, such as our bones. Unlike muscles, we can’t see our bones getting stronger, which makes prioritizing their health more challenging. To keep our bones healthy and safely reach our performance goals, our hormones play a vital role. 

The Role of Estrogen in Bone Health

Bone is living, dynamic tissue that continuously grows and changes – and estrogen plays a vital role in its health.¹ Estrogen helps the body absorb more calcium from the food we eat and slows down the activity of osteoclasts, the cells that break down bone.^2,3,4 Without enough estrogen, these cells can become more active, causing bone loss and potentially contributing to bone stress injuries that take months to heal.⁵

Why would an athlete lack estrogen? Whether intentional or not, athletes can end up in a state of low energy availability.⁶ Low energy availability is when you don’t eat enough to cover your exercise and bodily function energy needs, and your body begins to prioritize vital organs like the heart and lungs. 

“As a result, less critical physiological systems – such as the reproductive system – may shut down,” said Dr. Kate Ackerman. “There’s a drop in estrogen and other important hormones, which are then not available for bone.”^6,7

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Menstrual cycle irregularity is a symptom that doctors can track and connect to a person’s bone health. “If someone isn’t eating enough, they might lose their period, and then they can have low bone density,” said Dr. Ackerman. “This is the original ‘Female Athlete Triad’ that was first discussed in the early ‘90s.”^1,7

“The scientific community has now moved on from the original Female Athlete Triad to ‘Relative Energy Deficiency in Sport’ (REDs), recognizing that hormonal imbalances impact many different body systems,” added Dr. Ackerman.⁶ Athletes with REDs may also experience other changes to the body, such as cardiovascular dysfunction and metabolic disturbances. 

“Your missed period is one indication that you’re under-fueling, but it’s not the only one,” said Dr. Ackerman. “You can be under-fueling and still get your period.”

Researchers are still trying to understand why the order in which body systems are affected varies among individuals. For example, one person might experience muscle fatigue or cognitive changes before noticing menstrual irregularities. “This is an area of research that is ongoing,” added Dr. Ackerman.

MaligneRange/Wikimedia Commons CC BY-SA 4.0

Signs of REDs Beyond a Missed Period

The body’s response to low energy availability varies among individuals and is influenced by many factors, including genetics. Recognizing REDs involves identifying a combination of symptoms and risk factors.⁶ 

If you’re uncertain if you have REDs, consult a doctor who specializes in sports medicine or endocrinology. They may assess your dietary intake, recommend a DXA scan to measure bone mineral density, and request blood tests to evaluate levels of key hormones like estrogen, cortisol, and thyroid hormones. 

Keep in mind that you don’t need to have an eating disorder to develop REDs; you may simply be unaware you are not getting enough nutrients to fuel your training.

Debunking the Myth: Energy Deficiency and Hormonal Treatments

Hormonal replacement therapies are sometimes used to address bone mineral density issues. The efficacy of various treatments for improving bone health is a topic for another article, but they shouldn’t be seen as a complete solution.

“Hormonal replacement therapies are only a band-aid solution to the bone problem while you’re trying to fix the energy deficit,” said Dr. Ackerman. If you’re in an energy deficit, your body still won’t have the necessary resources to support all its systems properly.

To truly protect your bone health, you need to ensure you’re consuming enough nutrients to meet your body’s needs. A pill or patch with estrogen isn’t sufficient. Other activities like weight-bearing, multi-directional exercise also play a significant role.^1,8,9,10

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Dr. Ackerman highlights that everyone is different, and you may need to find a personalized approach for bone health that works best for you. Consult with an expert to ensure you are getting enough energy intake to meet your energy demands. 

To learn more about bone health, read our Playbook article “Start ‘Em Young: Prevention of Bone Stress Injuries in Athletes.”