Good morning all,
During our recent EMG lab, we considered muscle structure/function, and how muscle strength can be improved through enlargement of muscle fibers. We also noted that testosterone can support the development of larger muscles in both men and women. In the news this week is a report confirming that testosterone improves muscle and athletic performance in women, along with news of a strict limit on testosterone in female athletes being imposed by a track-and-field regulatory body.
Testosterone is a potent steroid hormone, produced in abundance by the male gonads (the testes). Testosterone is also found in women. The female gonads (ovaries) do not produce testosterone directly, but do produce several estrogens, which can be converted to testosterone by enzymes (especially in the brain). Both sexes also produce other androgens (male-typical hormones) in the adrenal glands, which also can be converted into testosterone.
So, we tend to think of testosterone as a 'male hormone', but the reality is not so simple. Both women and men have circulating testosterone, although men typically have levels that are 10-30x higher that those found in women. But, here too, our simplistic and convenient categorizations are not always reflected in reality.
While men typically have much more testosterone in circulation than do women, the range of variation in each gender is large. What of women who produce unusually large amounts of testosterone? Will that give them a muscular and a competitive advantage in sporting events? The anecdotal and the experimental evidence say that it will.
It is convenient to think of all persons as being purely binary in terms of their sex, such that all aspects of their sexual make-up (genetic sex, physical sex, physiological sex, gender identity) align to be either purely female or purely male, but the reality is, as always, more complicated. Persons of differential sexual development may not be perfectly aligned in all of their sexual characteristics, causing them to have characteristics which are not purely 100% typical of one gender or another. Apart from the social and physical challenges this poses, how such individuals can be evaluated in regulated sporting events recently has come into question. The most notable case has been that of the South African athlete Caster Semenya, a multi-medal winning foot race champion who has repeatedly been sanctioned because her testosterone levels are higher than the thresholds set for female athletes.
And what of athletes that are making a gender transition? Their testosterone levels are highly variable, and may fall within the male-typical or the female-typical range. Should they be barred from, or limited in, participation in sporting events?
These are important issues, beyond sporting regulation. Most aspects of society long have been male-biased, and it is becoming increasingly apparent that we suffer because of this. In science, it has become very clear that work done largely on male physiology serve females poorly. For decades, the standard experimental models for human physiology have been male mice and rats. Only one gender was used in order to reduce experimental variability. We long have known of differences in the female and male reproductive systems, but we never really appreciated how their influences translate into other systems (including the muscular system). But, now we are learning how surprisingly different male and female physiology outside of reproductive systems can be. And, the fact that this recent study of testosterone supplements in women was one of the first of its kind suggests that we have a lot of catching-up to do:
There is much to be learned about differences in female and male physiology and their implications for our health and well-being, and our scientific community is finally waking up to this fact. How the sporting community deals with the complexities of our physiology is of relatively little importance, perhaps. But the issue of equality in general, in science, health, and society, is one that recent generations have failed to properly address. May your generation be more open, more mindful, and more egalitarian.
Have a great weekend -
Good morning all,
As our term comes to a close, I'll use my last news message to send along the latest news from on ongoing story in exercise physiology that raises interesting, and difficult, questions about sex differences in physiology and the regulation of sporting events.
As we have described in class, both males and females have circulating testosterone, with males generally having much higher levels than females, on average. But, like all aspects of physiology, there is a wide range of what constitutes "normal" values, and there is overlap between the ranges of naturally-occurring male and female levels.
The science of testosterone is fairly well-understood in terms of its anabolic effects. Testosterone enables muscle fiber development to a larger size, and facilitates its maintenance at that size. Testosterone supplements have been used (both knowingly and unknowingly) for decades to help athletes build muscle, and its use was the primary factor which led to the formation of the World Anti-Doping Agency (WADA) and the associated regulations restricting the use of chemicals to enhance the physiology and performance of athletes, especially those competing in sanctioned (e.g., large, high-profile, big money) events.
Over the last few years in particular, however, we have gained an understanding that much of what makes us male or female is not always so perfectly discrete, so categorical. For some aspects of our genetics, anatomy, physiology, and performance, male and female traits are most often clearly binary (e.g., one way or the other). But other of our traits, especially some of our physiology, is not so dimorphic or discrete, and circulating testosterone levels fit into this category.
Males and females generally compete only within same-sex sporting events because, for most events, males hold a competitive advantage. This is certainly true for track-and field race events, which place emphases on speed and endurance. This is not to say that female athletes are in any way unimpressive or not elite - they certainly are, and many would leave male competitors 'in the dust'. But, in general, males outperform females in foot races, and testosterone seems to provide at least some of that advantage, through enhanced muscle size and performance.
Recent analyses have shown that the top female athletes in female track events have testosterone levels higher than the average woman. This is perhaps not a surprise, as these elite female athletes carry more muscle than the average woman as well. We must ask - which came first? Did higher testosterone promote more muscle, which led to racing success? Or does intense training lead to muscle development and an altered hormonal profile? Probably some of both.
This situation has reached a peak in recent years over the case of Caster Semenya, an Olympic medalist who hails from South Africa. By all published accounts, Caster is genetically and physically female, but exhibits hyperandrogenism, a state of producing greater than the normal amount of androgens (male hormones). She is the most-accomplished middle-distance female athlete of the last decade, to the point at which protests against her have been raised, and regulations put in place to prevent her from racing unless she takes medications to reduce her androgen levels. She has appealed those decisions, to no avail.
This issue raises many difficult considerations, from the personal (is this athlete being singled-out? Has her privacy been unfairly invaded?), to the social and political (is this another, familiar case of racism in sport?), to the athletic (is Caster really benefiting from her androgen levels?). As such, it seems unlikely to be settled easily, or soon. Nonetheless, it serves as a useful reminder that natural variability is, well, natural - it is an essential part of what allows us to exist as 7 billion different individuals. There are those among us who are short or tall, thick or thin, slow, - or very fast. Can we really regulate or legislate ourselves into categories, for competition, or for other reasons? Most of our physical and physiological traits vary broadly over a continuum, which means that drawing categorical boundaries may be somewhat artificial. In this case, we seem to have a single physical trait, with a well-understood connection to physical performance, that has become exposed in the very high-profile (and big-money) world of competitive sporting.
As we learn more about physiology, we are likely to revisit this issue many times again, and in new ways. How long will it be before we hear "Is it fair for me to compete against someone who has a better genetic profile than I do?". I suspect that, in the coming decades, we will be discussing less the physiological and hormonal aspects of physical and mental performance, but rather the genetic bases for them instead.
I'm signing off for the term now. I hope that these weekly news messages have been useful to you. This is the first semester that I have used them to this extent, and it has been a learning experience for me. In particular,
In the end, though, I remain very optimistic. Science is "mankind's organized quest for knowledge" (Floyd Bloom), and we already know that "knowledge is power" (Francis Bacon). It is science that offers us the best hope to deeper understanding, new therapies and treatments, new cures, and new adventures. We will encounter many speed-bumps along the way, to be sure. I hope that our course has inspired you to be a part of this quest, and to make the best use of the knowledge that you gain while on it.
Have a great weekend, and best of luck with all of your exams next week.