The Testosterone Deception E-Book

Robin Haring

• Herausgeber: Braumüller Verlag
• Kategorie: Ratgeber
• Sprache: Englisch
• Veröffentlichungsjahr: 2015

Seitenzahl: 255

Beschreibung

Most of us believe that more testosterone makes for more man. But what if this assumption is fundamentally wrong? What if the quest for authentic manhood is less determined by testosterone than we all thought? Bringing together extensive scientific research, author Robin Haring shows that testosterone is involved in virtually every aspect of life: relationships, work, health, sleep, diet, exercise, learning and sexuality. Drawing on the latest research in medicine, psychology and behavioral neuroscience, Haring not only reveals what testosterone can (and cannot) do for men, but also makes the compelling and radical argument that quality of life for men has very little to do with their testosterone levels and everything to do with their lifestyle. Presented with insight and humor, the book has a provocative and liberating message for all of us: testosterone levels are much more malleable than previously thought — which means that men are not doomed to be the passive victims of age-related testosterone depletion. But above and beyond this, the book has a subversive message. It says that your testosterone level is not — and ought not to be — the benchmark for successful living. Each individual man has the freedom to define this for himself. Because you are more than your testosterone level. Are you ready for that?

Leseprobe

Prof. Robin Haring, PhD

The Testosterone Deception

or how much testosterone do you need?

Prof. Robin Haring, PhD

The Testosterone

DECEPTION

or how much testosterone do you need?

ABOUT THE AUTHOR

Holding a PhD in epidemiology, Professor Robin Haring’s scientific work focuses on the role of low testosterone concentrations as a cardiovascular risk factor in men. With more than 50 publications in peer-reviewed medical journals, he has made a significant contribution to establish testosterone as a men’s health biomarker. For more information about the author see: robinharing.com

Bibliografische Information der Deutschen Nationalbibliothek

Die Deutsche Nationalbibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.d-nb.de abrufbar.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner.

DISCLAIMER

This book is intended to provide helpful and informative material on the addressed subjects, not as a medical manual.

The information given here is designed to help you make informed decisions about your health. It is not intended as a substitute for any treatment that may have been prescribed by your doctor. If you suspect to have a medical problem, we urge you to seek competent medical help. The author and publisher specifically disclaim all liability arising directly or indirectly from the use of this book.

Mention of specific companies, brand names, organizations or authorities in this book does not imply endorsement by the author or publisher, nor does mention of specific companies, brand names, organizations or authorities imply that they endorse this book, its author or the publisher.

First published in English 2014

Originally published in Austria in 2015 as Die Männerlüge

ISBN Printausgabe: 978-3-99100-146-1

ISBN E-Book: 978-3-99100-147-8

© 2014 by Braumüller GmbH

Servitengasse 5, A-1090 Vienna

www.braumueller.at

Translator: Michael Hale, Hamburg

Cover photograph: shutterstock.com | © Fer Gregory

ISBN 978-3-99100-150-8

Inhalt

Preface

Part 1

Testosterone – a character profile

Testosterone + men: fated to be together from the start

It ain’t over till it’s over

Nature is unfair

No medal without testosterone

Not for wussies

Harder than life

You need to have the right nose

Full beard or clean head? It’s your choice

Testosterone and the breeding eye

The price you’ve got to pay: fatherhood & low testosterone

New old fathers and the blessings of late fatherhood

Contraception – now men’s business?

Willing but not able, or not willing – Viagra and Flibanserin

Part 2

Men – testosterone-driven deficient beings?

Higher, faster, farther

Always over the top with testosterone?

Me, myself and I

Middle – Upper – Lower: Testosterone & social status

Show me your hand and I’ll tell you your testosterone level

You are your testosterone level, or aren’t you?

Testosterone and male behavior – one-way street or traffic circle?

Testosterone under the bell-curve

Part 3

Testosterone & men’s health

Risk factor man

Caution, highly flammable!

Honey sweet

Deadly quartet

Does low testosterone kill you?

Lost in thought

How risky is it, really?

Testosterone in the tap water?

The menopause – now available for men

“Aging male syndrome” – marketing gag or actual disease?

Testosterone replacement therapy: risks, benefits and options

Part 4

Testosterone & lifestyle

As old as Methuselah and still enough testosterone

Keep moving

Tofu or meat power?

Take it easy

The late bird catches the worm

Just do it?

No gender gap for monks

Menopause, andropause or never pause for any cause?

Testosterone is for everyone

Part 5

Testosterone & the crisis of man

Happy despite low testosterone?

Less is the new more

What makes a man a real man?

Testosterone and the battle of the sexes

Epilog

References

Preface

We’ve never had so much testosterone! Whatever the topic – the world economic crisis, the Olympic Games, mandatory job quotas for women or the European Union rescue package for Greece and Spain – whenever the major issues of our time come up for discussion, the magic word “testosterone” never fails to make the stage. The accusations made against testosterone are as simple as they are ubiquitous: testosterone inflames the greed of Wall Street bankers; testosterone prevents women from reaching the upper echelons of managerial power; testosterone is bringing the world’s economy to its knees; the world is racing to its doom in a testosterone haze and so on and so forth. The atmosphere is now so heavily laced with testosterone that it’s almost possible to become pregnant just by breathing. Testosterone is, of course, considered to be the most important male hormone, but aren’t all these claims just a little bit over the top?

The time is ripe for a better understanding of the role testosterone plays in men’s lives. Testosterone is routinely blamed for everything from male infidelity to economic collapse and – thanks to Lance Armstrong, Jane Fonda and the catastrophic effects of testosterone-driven investment banking – it is by far our most prominent hormone, appearing in the news literally on a daily basis. On top of this, global testosterone sales increased 12-fold over the last decade – an expansion in consumption fueled by the ongoing debate about the existence or non-existence of the andropause (the “male menopause”) and the diagnosis of a brand new condition known as “Aging Male Syndrome.” In the context of the discourse about healthy aging and longevity, testosterone is closely identified with notions of vitality, vigor and sexual agility in an aging American population.

As a testosterone researcher, I felt an ever-growing need to inform the lay public about the current state of testosterone science. This book is the story of what we know and what we are learning about testosterone. It is written within the context of scientific research into the subject, and the following chapters describe the various pieces of the testosterone puzzle, which I have divided up into four major parts: biology, behavior, health and sociology. Part 1 describes the long and tortuous history of the discovery of testosterone and examines the physiology of male testosterone (where does it come from?), as well as its basic function in men (what does it actually do for us?). Although some people might assume otherwise, the field of testosterone research is full of surprises, and throughout the book I use examples from a number of scientific studies, as well as the animal kingdom, to demonstrate this.

Having given the reader an insight into the complexity and richness of the physiologic processes underlying testosterone production in men, the stage is then set for Part 2. In this section of the book, I attempt to address some common misconceptions about the testosterone-like nature of manhood. These chapters present the current state of knowledge about testosterone and its effects on male behavior and explore major areas of life such as relationships, work, decision-making, emotions, social life and – last but not least – sex. They also attempt to answer the following questions: To what extent does testosterone drive male behavior?

Is every social interaction poisoned by testosterone?

Does testosterone fuel egocentric choices, risk-taking behavior or the will to power?

Part 2 ends with some surprising insights about the reciprocal – or, rather, circular – relationship between testosterone and behavior. Testosterone does, of course, drive male behavior to a certain extent, but on the other hand, the actions we perform and the choices we make in our daily lives also impact on our testosterone level. No matter what we do – whether it’s watching a sad movie, becoming a father for the first time, oversleeping or doing endurance training – all of these things are resonated by our endocrine system in general and our testosterone level in particular. So in this section of the book, I attempt to turn the received notion that testosterone begets behavior on its head and consider scientific evidence showing that the way you live your life affects how much testosterone you have.

Part 3 describes the latest scientific research (including my own) into the role played by testosterone in men’s health and also deals with a number of pressing questions: Why do men with low testosterone levels face a higher risk of suffering from hypertension, adiposity or diabetes? Why do men with low testosterone levels even die earlier compared to men with normal levels? Does low testosterone actually cause these adverse events, or only indicate them? Is testosterone the reason why women live five years longer than men on average?

In this section, I also question the existence of the condition that has been sold to the public as “Aging Male Syndrome” and ask: Is the “andropause” a medical fact or fiction? Is there any hard scientific evidence behind these buzzwords? What is the true risk-benefit-ratio of the testosterone replacement therapies that promise us more testosterone in exchange for our dollars?

In Part 4, the final section of the book, I explore the implications of the many delusions that have grown up around testosterone. Giving examples from a number of past and recent studies, I examine the scientific community’s unfortunate tendency to use differences in biological features such as brain weight, finger ratio and hormone levels (i.e. testosterone) as an explanation for economic, social and cultural issues. In these chapters, I also conduct a debate with the discipline of sociology on the relevance of hormones (in particular testosterone and estradiol) in the battle of the sexes. Given the bestselling recent forecasts about The End of Men (by Hanna Rosin), I question the use of testosterone as a biological explanation for the shifting power dynamics between men and women and challenge the testosterone-driven perspective on manhood favored in popular behavioral and gender research.

Contrary to zeitgeisty claims about the looming extinction of manhood, Part 4 helps us to see how men can adapt to the ever-changing reality of today’s world in the quest for an authentic manhood beyond the prevailing myths about testosterone.

In the same way that we can see some things through the lens of the human eye and other things through the lens of a microscope or a telescope, testosterone can also act as a lens through which we can gain important new insights into our everyday lives and surroundings, thus adding to our knowledge of the wondrous world we live in. Consequently, this book will – hopefully – not only change your perspective of (male) human nature and aging, but also improve your chances for doing what needs to be done to make the best of it.

Although it would be better to read the book from start to finish, I’ve conceived it in such a way that it’s also possible to begin at any chapter you like, to skip chapters, or simply skim through it. But however you decide to enjoy this book, I definitely want reading it to be fun, and for this reason I decided to spare my readers the usual scientific obsession with details. Anyone wishing to gain a deeper knowledge of the subject should see the numerals that I’ve placed at the end of many sentences. These refer to the corresponding scientific articles listed at the end of the book. But for now I would simply like to wish you an interesting and enjoyable journey through the world of testosterone.

Part 1

Testosterone – a character profile

Name: testosterone

Family: sex hormones

Big sister: estrogen

Big brother: dihydrotestosterone

Parents: cholesterol

Place of origin: testicles (95%)

Born: 1935

Discoverers: Adolf F. J. Butenandt and Leopold Ružica

Amount produced: 6-7 mg per day

Hobbies: track and field, cycle racing, politics, investment banking

Awards & prizes: Nobel Prize for Chemistry, 1939

Physique: 19 ring-like carbon atoms surrounded by hydrogen and oxygen

Best friends: endocrinologists, andrologists, professional sportspeople

(and those wishing to become professionals)

The birthplace of testosterone lies in the middle of Zurich, in the historic chemistry building of the venerable Swiss Federal Institute of Technology. At the end of the 19th century, the institute’s chemistry department attracted large numbers of chemists due to its excellent working conditions and modern laboratories. Among these were Adolf F. J. Butenandt and Leopold Ružica. There, in 1935, the two chemists succeeded in being the first to create the male sex hormone testosterone artificially from cholesterol.1 The hormone was christened, however, by the German pharmacologist Ernst Laqueur. He had already isolated the hormone from bovine testicles earlier that year and created the artificial compound word “testosterone” from “testis” (testicle) and “steroid” (sex hormone). For their discovery of the structure of testosterone in 1939, Adolf F. J. Butenandt and Leopold Ružica were awarded the world’s greatest scientific award, the Nobel Prize. Less than two years later, laboratory-manufactured testosterone was used for the first time in the medical treatment of sexual underdevelopment.2 Just one year after testosterone treatment, patients experienced a deepening of their voices, increased hair growth and more frequent erections: the 100-year-old puzzle surrounding male potency seemed to have been unraveled.3

As early as 1849, an experiment on castrated roosters had led Arnold Berthold to suspect the existence of hormones. He observed that after undergoing a testicle transplant, a castrated rooster regained full sexual functioning. He was unable, however, to come up with a plausible explanation for this phenomenon. As it didn’t matter where the testicles were transplanted onto the rooster’s body, he came to the conclusion that the effects of the transplant must occur via the bloodstream and not via the nervous system. At the time, this was an almost revolutionary idea and – like so many revolutionary ideas – it was initially rejected by the scientific community. More than 80 years were to pass before the discovery of testosterone proved that the “father of endocrinology” – as Berthold is now respectfully known – had been right all along. By this time, however, he was dead.

Between these two dates, a number of fantastic treatments for the rejuvenation of male potency were recorded. On June 1, 1889, Charles Édouard Brown-Séquard appeared before the French Biological Society in Paris and announced that he had discovered the “fountain of youth.” In an experiment now regarded as legendary, the 72-year- old infirm neurologist and physiologist injected himself with a liquid extract taken from the testicles of dogs and guinea pigs. And he was more than happy with the results, feeling physically stronger and mentally more alert. Without any prompting from the audience, he informed those gathered in the auditorium that his constipation was now cured and that he was once again capable of releasing a strong, high jet of urine. Although his colleagues were skeptical about his claims, he insisted that there was a direct correlation between the injection and the beneficial effects he was now experiencing.

We now know that a much higher dosage would have been required to achieve the results described by Brown-Séquard. In the final analysis, the correlation between the extract and the effects he claimed for it remained unclear, as the size of the study sample never exceeded the number one (himself). Seen from a modern perspective, Brown-Séquard’s “fountain of youth” was probably just the product of a massive placebo effect.

This did not, however, prevent business-minded imitators such as the famous French surgeon Serge Voronoff from making a killing by transplanting chimpanzee testicles on to well-off, elderly men. The 100,000 gold francs that Voronoff charged per operation would now be worth 340,000 US dollars! In the 1930s, thousands of these transplants were performed all around the world. So many, in fact, that at times it was impossible to keep up with the demand for chimpanzee and baboon testicles. However, this entire business boomed without being aware of the actual source of male virility: testosterone.

More than 40 years were to pass between Charles Édouard Brown-Séquard’s first experiment on himself and the pioneering work conducted by Adolf Butenandt, for which he collected 15,000 liters worth of urine samples from Berlin police officers. From these 15,000 liters of urine he was able to distill 0.0015 grams of the male sex hormone and subsequently unlock the secret to its structure. The rest, as the saying goes, is history.

Nevertheless, Charles Édouard Brown-Séquard is still regarded as the founding-father of endocrinology, the study of the structure and functioning of hormones. Because although the term “hormone” (from the Ancient Greek hormān: drive, stimulate, set in motion) was not coined until 1905), his hunch that a depletion of certain substances in the human body could be counteracted by using extracts from animal organs finally turned out to be correct.

Testosterone + men: united forever

The exact difference between a man and woman is just 27 centimeters. I’m not referring here to the male organ of reproduction, but to SRY, the “male gene,” which was discovered in 1991.4 Scientists had been aware for quite some time that all human beings – men and women – begin their lives as female fetuses. But before the discovery of SRY, they had not been able to explain how genes and hormones interact with each other, with the result that carriers of the Y-chromosome develop into full-blown males. In order for the original program – which is set to “female” – to create a male baby, a hormonal switch has to be thrown. Only after the sixth week of pregnancy does the male Y-chromosome become active, resulting in the development of embryonic testicles. From the eighth week of pregnancy onwards, the testosterone factory swings into action, and by the time it reaches full production in the sixteenth week, what started life as a female fetus has now become a male – mission accomplished. At this point, the testosterone level of male fetuses falls again, leveling off at roughly equal in boys and girls by the 26th week of pregnancy.

After their birth, boys once again experience a similar rise in their testosterone level, but this drops off again after about three months. While the first burst of testosterone in the womb is responsible for the formation of the male sexual organs and for turning girls into boys, the reason for the post-natal rise in testosterone has yet to be discovered. There’s also still no explanation as to why those babies that just can’t wait to get out into the big, wide world (born after 32 weeks) have higher testosterone levels than those babies that are content to hang on in the womb for a while longer (born after 40 weeks).5 In any case, as a memento of their short spell as women, men’s bodies have a number of superfluous characteristics, such as nipples.

However, the process by which fetuses are transformed from their original female state into males is extremely prone to interference. A number of influencing factors can lead to intermediate states that are neither clearly male nor unambiguously female. A good illustration of the difficulties faced by doctors in such cases is provided by 800-meter world champion Caster Semenya. After the young South African woman unexpectedly won the gold medal at the 2009 World Championships in Athletics, which were held in Berlin, people immediately began to voice suspicions about her gender. Semenya’s masculine facial features, deep voice, muscular physique and clearly defined six-pack only increased the skepticism as to how female she actually was. But because Semenya showed up negative on all the relevant doping tests, her success in Berlin was simply put down to an overdose of testosterone. But could it be that Semenya is a XY-woman?

XY-women look like normal women, but their genetic make-up corresponds to that of a man. As we’ve already learned, a sudden, massive increase in testosterone at a specific point during pregnancy has an irrevocable effect on the sexual and physical development of the fetus. If this “testosterone surge” doesn’t kick in at exactly the right time, the development of the fetus in favor of one sex or the other comes to a standstill, and it is left in a kind of inter-gender limbo. In order to achieve its full effect, testosterone has to find its way from the bloodstream into the cells via so-called androgen receptors. However, XY-women carry a genetic mutation within them that blocks the androgen receptors, thereby rendering testosterone ineffective. This results in an absence of male physical characteristics such as bodily hair and a penis and testicles. Although there are varying degrees of resistance to testosterone, in its most extreme form – complete androgen resistance – the effects of testosterone are neutralized completely and babies that are genetically male are unable to break out of the basic female programming. The result is a boy that grows up as a girl. In many cases, XY-women are only identified as such with the onset of puberty, when they fail to start having their period. The acute identity crisis that XY-women then go through (am I a man, a woman, or both?) is made even worse by the realization that they will never be able to bear children, as they have neither a womb nor ovaries.

In any event, it took the International Olympic Committee (IOC) and the International Federation of Athletics Associations (IAAF) two years to come up with new rules of competition following the Semenya case. Since the London Olympics in 2012, the following regulation has been applied: XY-women with male levels of testosterone are only allowed to compete as women if it can be proven that they have altered testosterone receptors – in other words that they are resistant to testosterone and don’t have a competitive advantage over other women as a result of their higher testosterone level. As far back as the Olympic Games in Atlanta in 1996, a total of eight genetic males were discovered among the 3,387 “female” athletes (1:423).6 However, they were still allowed to compete as XY-women, as they didn’t react to the higher levels of testosterone in their bodies.

At any rate, the concept of two clearly defined sexes now seems to be completely outdated. A “Y” in the chromosome pair would have resulted in an unequivocal “That’s a man!” 30 years ago. Today, however, the dividing line between the sexes is seen as fluid. Neither chromosomes, nor hormone levels, nor internal and external genitalia allow for clear gender classification. But if the biological criteria for determining a person’s sex are so ambiguous, could one argue that gender is a cultural, as opposed to a biological category? Or are men, as Simone de Beauvoir famously argued, not born but made? We’ll return to this question later.

It ain’t over till it’s over

After the first gush of testosterone in the womb has set the switches for the development of a male child, a further burst is necessary in order for the boy’s final, irrevocable sexual maturation to take place. During puberty (from the Latin pubertas “sexual maturity”) a significant increase in testosterone triggers the emergence of secondary sexual characteristics (bodily hair), the ability to reproduce (sperm production) and a noticeable increase in height. However, the exact time-span to which the term “puberty” can be applied is still the subject of intense scientific debate and research, because even in normal, healthy individuals, puberty begins and ends at different times. At the moment, scientists are in agreement about just one thing: young people are entering puberty and achieving sexual maturity earlier and earlier as time goes by, with the result that an 18-year-old today is as physically well developed as a 22-year-old would have been in around the year 1800. The most probable explanation for this is that improving dietary and health conditions are causing boys and girls to reach sexual maturity at an increasingly earlier age.

This trend is confirmed by the medical adviser to the world famous St. Thomas Choir of Leipzig, Michael Fuchs. According to the usual timing, a boy’s voice breaks right in the middle of puberty. The rush of testosterone that boys receive during puberty causes their throats to increase in circumference by about 40%, and the vocal folds in the larynx become thicker and almost double in length. This causes the pitch of the voice to drop by a full octave (interval of eight notes) and transforms delicate boys’ voices into full, manly basses.

A long-term study of budding singers from the world-famous St. Thomas Choir of Leipzig proves that boys’ voices are breaking earlier and earlier. Whereas in Johann Sebastian Bach’s day (Bach was director of the choir from 1723 to 1750), choirboys’ voices were breaking when they were about 17 or 18 years old, this now usually happens when the boys are 15 years old, and in some cases when they are as young as 11 or 12 years old.7 In order to predict the approaching drop in pitch and thus make it easier to plan the lineup of the choir and look after the singers’ voices more effectively, 36 boys from the St. Thomas Choir of Leipzig were subjected to a series of tests every three months over a period of three and a half years. The tests measured ten vocal and eight non-vocal parameters. However, at the end of the study, only one parameter was able to provide a reliable prognosis as to when a boy’s voice would begin to break. I’ll give you three guesses which one it was? His testosterone level. Using this, it was possible to ascertain that about 16 months elapse between the first rush of testosterone and a boy’s voice breaking. None of the other parameters used was able to produce such a precise prediction. Subsequent research into testosterone trajectories proved their potential as a useful measure to examine pubertal dynamics.8

But why do boys’ voices break during puberty at all? The answer has its roots in human evolution: the deeper a man’s voice is the greater his chances of attracting a mate. A deep male voice is a sign of high testosterone levels and signals potency, determination and aggression. And a deep male voice also leaves traces in the female memory. Researchers from the University of Aberdeen in Scotland showed 912 women a picture of a single object and simultaneously played them recordings of different voices saying the name of the object. Then the researchers brought out two similar, but non-identical versions of the object they had shown the women and asked them to say which one they had seen. The result: if an object was accompanied by a deep male voice, the women were much better able to remember it. In addition, the women reported that they found bass voices much more agreeable than high voices.9 In this way, a sonorous bass voice buries itself deep in the female memory and recommends its owner as a powerful, strong-willed provider.

However, the fact that boys’ voices break is still a comparatively harmless symptom of puberty; a period that is also accompanied by a sudden increase in fatal accidents, dangerous showing off and excessive risk-taking among teenage boys. Fatal accidents might still be a relatively rare occurrence, but the rate does rise from 1:10,000 at the age of 13 to 5:10,000 by the age of 18. With the aid of this “accident hump” – which also occurs in male primates – the demographer Joshua Goldstein was able to indirectly provide additional evidence for the earlier onset of sexual maturation. Goldstein discovered that the accident hump has been starting approximately 2.5 months earlier per decade since the year 1750.10 But although adolescents are reaching sexual maturity at an increasingly early age, they are at the same time attaining the social status of adulthood at an increasingly later age. For a good half a century now, the age at which young people marry, raise a family, start work and become financially independent of their parents has been rising. Research into the development of the brain points in the same direction, indicating that puberty is now lasting until young people are 24 years old.11

But regardless of the exact beginning and end of puberty, nature seems to have adapted itself to the accident hump and takes the precaution of providing a ratio of 105 male to every 100 female births. Although this relationship is subject to slight variations, these have nothing to do with testosterone. As surprising as it may seem, variations in temperature result in an altered sex ratio at birth, whereas testosterone hardly reacts at all to seasonal influences. During a cleverly worked out comparative study, three blood samples were taken from 121 men at three-month intervals. This showed that daily fluctuations in male testosterone levels are much stronger than seasonal long-term fluctuations.12,13 On the contrary, scientists evaluated Scandinavian church registers going back 150 years and discovered that for every extra degree in temperature, roughly one per cent more boys are born.14 This, of course, casts a whole new light on the consequences of the prevailing climate change. I can already see the tabloid headline: “Global warming leads to a world of men!”

Nature is unfair

Although, according to Albert Einstein, “God doesn’t play dice,” (which was his way of saying that the universe should be explained by solid, deterministic laws) men of the same age sometimes have wildly differing testosterone levels – something for which there is still no logical explanation. The proportion of genetic factors that influence a man’s testosterone level is estimated by scientists to be around 50%.15-18 But exactly which genetic factors play a part in the regulation of male testosterone levels was completely unclear until recently. Only the evaluation of data gathered from over 14,000 men made it possible to identify the genetic factors that influence male testosterone levels.19 The fact that the genetic variations that were discovered to be linked to testosterone levels are located on the SHBG gene should come as no surprise to scientists, as SHBG codes for a protein that binds testosterone in the blood. However, the lead author of the study, Professor Claes Ohlson from the University of Gothenburg, suggests that the genetic factors his team identified have comparable effects to non-genetic factors on testosterone levels and could be used clinically to identify men who are at risk of low testosterone. But even in the light of these brand-new insights into testosterone’s genetic underpinnings, is it really possible to determine a “normal” testosterone level?