Intended for healthcare professionals


Sex, gender, and sports

BMJ 2019; 364 doi: (Published 20 March 2019) Cite this as: BMJ 2019;364:l1120

Re: Sex, gender, and sports

Dear Dr. Dixon, Dr. Bermon et al.,

Thank you for your comments on our Editorial. Individual-level analyses would perhaps enhance our understanding of the link between serum testosterone levels and athletic performance among intersex women compared to non-intersex women. However, even if privacy laws permitted access to these data, it would still prove difficult to show causal associations independent of so many other contributing biological and non-biological correlations.1 Requiring athletes with naturally high testosterone levels to reduce their blood level of testosterone with hormone suppression or surgery is unscientific - and not without potential risk- since by definition, individuals with differences of sex development have alterations in the way they process androgens at the cellular and tissue level, as explained in detail in Dr. Bermon et al.’s review article.2

A nuanced understanding of endocrinology and sex hormone physiology indeed facilitates informed opinions on the IAAF’s deliberations for categorizing female athletes, because the intracellular metabolism and downstream effects of androgens and estrogens are extremely complex. One of the authors of our editorial includes an internal medicine specialist and gender medicine scientist who has previously published on sex hormone variability, measurement error and the sensitivity/specificity of blood hormone samples at a given point in time.3 The other author is a sports science, injury prevention policy scholar and gender equity advocate. Both authors believe in data-informed decision-making, scientific integrity and merit-based, equitable access to discipline-specific recognitions and awards.

Having credentials does not mean that interpretation of the literature is straightforward or that decisions about eligibility for the sex category, or any other category in sport, are easy to make; different views need to be acknowledged, considered and respected. To this end, our editorial clearly acknowledged the bimodal distribution of testosterone in non-athletes but also cited additional studies that showed overlap among athletes, the lack of a validated test for androgen sensitivity, and the questionable relationship between testosterone levels alone and real-time sports performance. Because of BMJ’s restriction on the number of citations for editorials, we regretfully were unable to include Dr. Bermon et al’s review.


Cara Tannenbaum MD, MSc (internal medicine, epidemiology and biostatistics)
Sheree Bekker PhD (sports science, injury prevention)


1. Healy ML, Gibney J, Pentecost C, Wheeler MJ, Sonksen PH. Endocrine profiles in 693 elite athletes in the postcompetition setting. Clin Endocrinol 2014;81: 294–305.
2. Handelsman DJ, Hirschberg AL, Bermon S. Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance. Endocr Rev 2018;39(5):803-29.
3. Tannenbaum C, Barrett-Connor E, Laughlin GA, Platt RW. A longitudinal study of dehydroepiandrosterone sulphate (DHEAS) change in older men and women: the Rancho Bernardo Study. Eur J Endocrinol. 2004;151(6):717-25.

Competing interests: No competing interests

23 April 2019
Cara Tannenbaum
Professor, Medicine and Pharmacy, Université de Montréal
Sheree Bekker
4565 Queen Mary Road, Montreal, Quebec