Portal de Periódicos da CAPES

Testosterone

2015; Wiley; Volume: 227; Issue: 6 Linguagem: Inglês

10.1111/joa.12388

1469-7580

Gillian Morriss‐Kay,

Hormonal and reproductive studies

By J. Herbert. ( 217 pp. ISBN 978-0-19-872497-1; hardback; £16.99/$29.95.) Oxford: Oxford University Press. 2015. This book is a fascinating account of one of the most potent physiological forces that drives human behaviour and influences social structure. It takes a broad view of the subject, summarised by the subtitle sex, power and the will to win. The writing style combines an effervescent enthusiasm with a refusal to simplify the subject for the sake of presenting a neat story. The scientist reader will appreciate the intellectual rigour of this careful approach, although it sometimes sits awkwardly alongside explanations aimed at the lay reader. I enjoyed the many quotations from other writings that pepper the text and precede each chapter. These range from the predictable (Darwin, Pinker, E. O. Wilson, Hippocrates) to the less expected (Flora Thompson, Hillaire Belloc, Louis de Bernières) and the specialised (Carl von Clausewitz, Niall Ferguson and Rupert Brooke in the chapter on war). I found the distribution of other ‘extras’ into footnotes and numbered endnotes less congenial, as they disrupted continuous reading of the text. The first chapter sets testosterone in an evolutionary context. Although the title indicates that it is about human evolution, it is much broader than that and begins with a section on the brain and an account of female mammalian reproductive cycles that I found rather tedious. The word ‘testosterone’ is not even mentioned until page 11 – some explanation as to why ‘a book on testosterone has to start with consideration of the way that females breed’ (p. 11) might have made the first 10 pages more welcoming had it come earlier. However, the scene is soon set for the chapters that follow – ‘The tendrils of its powerful actions creep into much of what we do’ (p. 14). The basic molecular biology of testosterone is covered in chapter 2. This is a difficult topic to explain to the lay reader, but is generally well done except that figure 7 comes too early – the acronym SHBG is not explained until four pages later, and it is puzzling that the androgen receptor is illustrated out of context in the next chapter. The observation that only 5% of blood testosterone is unbound, and hence available, is an important point clearly made, and I was interested to learn that the sensitivity of the androgen receptor varies in inverse proportion to the number of its CAG repeats. Chapter 3, ‘Testosterone Makyth Man’, is wide-ranging and fun but, as always, warns against generalisation. It assesses the evidence that prenatal and early postnatal testosterone influences male-type behaviour, sexual preference, gender identity and the 2D : 4D finger ratio (so what am I to conclude from my own male-type finger pattern?). Chapter 4 covers the subject of testosterone and sex in a straightforward and competent manner, providing a context of non-primate mammals and primates before considering human sexuality and sexual attractiveness. The book then moves into more dynamic territory with chapters on aggression, how winning and losing affects (and is affected by) testosterone levels, and war. Here we are engaging with the core link between testosterone and masculinity. There are of course exceptions – women are found among FTSE traders and soldiers, but their very rarity underlines the strength of the link. It is only in sport and in non-physical competition that women's ambition commonly equals that of men, and I was disappointed that the relationship between testosterone and competitiveness was not discussed in the context of the areas in which both women and men participate in equal numbers and with equal enthusiasm, if not equal muscle power. These four chapters consider the relationship between competition, aggression, risk-taking and reproductive success, and the importance of undertaking a cost–benefit analysis to assess the likelihood of winning. Because these individual testosterone-driven behaviours are not conducive to social harmony, both human and primate societies have evolved complex ways of controlling them. As the author points out, social controls are important for maintaining genetic diversity as well as for controlling promiscuity and conflict. The most interesting and informative studies on testosterone and risk-taking have been carried out on the trading floor; these are described in some detail. Apparently two elements are involved: an emotional (fast) response involving the amygdala, and a slower, more logical appraisal that involves the anterior cingulate gyrus and seems to be less testosterone-dependent. The balance between the two needs to be adjusted in relation to an assessment of how many losses can be sustained to maximise the probability of a major success. Decisions about the costs and benefits of conflict are also relevant to the decision to make war (Chapter 8). Although oxytocin plays a role in inter-male bonding, it is principally testosterone that governs the ‘aggressive propensities, competitive traits, a tendency to form alliances with other group members but to be hostile towards strangers, territoriality’ (pp. 142–143). This chapter ranges over international conflict, street gangs, bikers, football teams and gentlemen's clubs. It also considers fanaticism as an extreme form of group identity and loyalty to a cause and/or leader. After four quite racy chapters about behaviour in which testosterone and maleness are almost synonymous, a chapter on testosterone in women follows. I suppose it is only to be expected that it is relatively short, but even so I found it disappointing. There is, it seems, ‘confusion and uncertainty about the role of testosterone in women’, the one positive piece of information being that testosterone is concerned with sexual interest (receptivity) as opposed to sexual attractiveness, which is controlled by oestrogen. Apparently ‘the common idea that women who succeed in roles that are more often occupied by men must necessarily have more testosterone is a fallacy, though a common one’. Unlike all the other statements in this book, this important one lacks data or a reference to support it. And I don't believe that women are worse map-readers than men, even if we are poor at route-finding without maps. More data or references please! I also regret the lack of a counter-story: the roles of testosterone are of course the main subject of the book, but in a chapter on women, the fact that we have only low levels of this hormone deserves more consideration than it is given. For instance, a lesser tendency to risk-taking is surely an important source of stability in our traditional role as the primary caretaker. And I wanted to know whether the claimed female characteristics are consistent in Androgen Insensitivity Syndrome women, who have lacked testosterone influences on their bodies and brains from embryonic stages onwards, or in the former East German athletes who were given testosterone as young women and are now appealing for compensation because of the long-term effects. The book ends with a very well-written chapter on testosterone and the brain. The figure showing sites of androgen receptors is clear and informative but I was puzzled by the purpose of the illustration of a rat brain that had no relevance to the text. An illustration showing all of the human limbic system components mentioned, not just two of them, would have been helpful. These are minor criticisms; in general this chapter covers the topic well and forms a fitting end to the book. It summarises the overall theme that testosterone drives human male sexuality and its attendant behaviours, while mechanisms derived from cortical functions keep its effects within acceptable limits (potentially, at least). In spite of my complaints that the book did not specifically address some of my own interests, I warmly recommend it to both male and female readers of this Journal as a rewarding, informative and enjoyable read. I hope to see some of my reservations addressed in a second edition.