Do athletes with Disorders of Sex Development (DSD) have a physiological advantage in sports?

Physiological Advantages of Athletes with Disorders of Sex Development (DSD)

Athletes with Disorders of Sex Development (DSD) typically have significant physiological advantages in sports competition due to higher testosterone levels that contribute to increased muscle mass, bone density, and oxygen-carrying capacity.

Understanding DSD and Athletic Performance

Disorders of Sex Development (DSD) refer to conditions where chromosomal, gonadal, or anatomical sex development differs from typical patterns. The primary physiological advantage in athletes with DSD stems from hormonal differences, particularly testosterone levels.

Key Physiological Advantages:

1. Testosterone Effects

   • Athletes with certain DSDs (particularly 46,XY DSD) may produce testosterone in the male range—10 to 20 times higher than typical female ranges 1
   • Testosterone has potent anabolic effects on muscle mass and bone density
   • Stimulates erythropoiesis (red blood cell production), enhancing oxygen-carrying capacity 1

2. Musculoskeletal Advantages

   • Greater muscle mass and strength
   • Enhanced bone mineral density
   • Improved power-to-weight ratio

3. Cardiovascular and Respiratory Benefits

   • Higher hemoglobin concentrations
   • Enhanced oxygen transport capacity
   • Potentially improved cardiac output

Scientific Evidence on Performance Advantages

The most recent evidence indicates that sex differences in athletic performance are profound and primarily attributable to the direct and indirect effects of sex-steroid hormones 2. These differences:

• Exist before puberty
• Increase dramatically as puberty progresses
• Result in males outperforming females in events determined by strength, speed, power, endurance, and body size 2

For athletes with 46,XY DSD competing in the female category, these advantages may persist even with hormone therapy. The International Federation of Sports Medicine (FIMS) consensus statement notes that there may be lasting advantages from previously high testosterone concentrations 3.

Controversies and Alternative Perspectives

Some researchers challenge the testosterone-centric view of advantage. Ferguson-Smith argues that Y chromosome genes for stature (and possibly other genes) may be responsible for the increased frequency of 46,XY DSD among elite female athletes 4. This research suggests that in many cases:

• Androgens may be non-functional or absent
• Testosterone alone cannot explain athletic success
• Genetic variation plays a major role in athletic performance 4

Regulatory Approaches

Sports governing bodies have implemented regulations based primarily on serum testosterone levels to determine eligibility for female competition. However, these approaches have limitations:

• Lack of comprehensive sports performance data before, during, or after testosterone suppression 3
• Need for sport-specific policies based on peer-reviewed scientific evidence
• Recognition that even evidence-based regulations may not eliminate all performance differences 3

Health Considerations

Athletes with DSD may require hormone replacement therapy (HRT) if their gonads are removed or if they have impaired sex steroid production 5. This treatment is essential for:

• Inducing or maintaining secondary sexual characteristics
• Optimizing bone health
• Promoting physical and social well-being 5

Conclusion

While there is strong evidence that athletes with certain DSDs (particularly those with XY chromosomes and high testosterone levels) have physiological advantages in sports competition, the scientific community continues to debate the extent and nature of these advantages. Current regulatory approaches focus on testosterone levels, but emerging research suggests more complex genetic factors may also play important roles in athletic performance.