NFS302 Lecture 5: Testosterone and Sports

Is there a “Sports gene”?

• Almost certainly not

• BUT, there is a sports hormone → testosterone (C₁₉H₂₈O₂)

What is Testosterone?

• A steroid=based androgenic hormone produced primarily in the gonads

• Androgenic = derived from Greek (“man” + “produce”)

  • Men produce ~2.5-10 mg/day

  • Men produce at least 10x more than women (generally, but up to 20x)

Testosterone Reference Ranges

• “Ideal” range depends on who you ask, and we use different units in Canada vs. US

• Testosterone reference:

  • 8.4-28.8 nmol/L (Canada)

  • 242.2-830.6 ng/dL (US)

  • As long as you are in this range, it doesn’t really matter how high/low you are

• Free testosterone reference: 196-636 pmol/L

• 34.7 nmol/L (1000 ng/dL) or higher → disqualification from a natural bodybuilding competition

  • Would assume you are using exogenous test

What is Estrogen?

• All estrogen comes from testosterone (or other androgens)

  • Female sex hormone

• Enzyme aromatase: converts testosterone and other less active androgens → estrogen

  • Male bodybuilders may take things to downregulate this enzyme and prevent this reaction

Humans with more testosterone are…

• Bigger, taller, faster, stronger

• More aggressive

• Higher proportion of lean muscle mass

  • Regardless of sex, if you give someone testosterone, these things will generally happen

Sex as a Biological Predictor

• Biological sex has one of the strongest correlations to performance and athletics

• There are relevant differences between men/women and overall health

• Women are the underrepresented sex → much harder to get information that is applicable to them

Variables Predictive for Health and/or Behaviour

• These variables are not that important on their own, but are predictive of something WAY more important

• Factors: sex, cholesterol, BP, eating nuts, bone mineral density, BMI, vegetable intake, pushups number, IQ, HbA1c, age, VO₂ max

  • Some more impactful than others

5 words to live by

1. Be nice

2. Don’t tell lies

The Super Man

• Evolution in male genetics for fighting and athletic performance

• Beard: hides and protects the jaw → keeps you from getting knocked out

  • Females are more likely to get concussed in sports

• Jaw: evolved to ↓ likelihood of getting knocked out

• Humans use hands and fists for fighting

• Strength difference between men/women is disproportionate in upper vs. lower body

History of “War” in Male Genetics

• Winners get to procreate, losers die

• Minor changes in number of reproducing females and a more stable female population

• Dramatic reduction in number of reproducing males (ratio of 1:17)

• Violent intergroup competition preferentially taking place between members of male descent groups

• Group extinction → extinction of lineages

T&F world records

• males are significantly faster (~10-12%)

Roger Bannister

• Makes history in 1954 by becoming first human to run a mile in <4 min

• Since then, ~1400 male runners have gone on to do this

  • No female has done this yet

Peres Jepchirchir

• WR holder in women’s only marathon

  • 2 hr 16 min 16 sec

• Her WR time is beaten by 250-300 different men every year

Christian Coleman

• Won gold medal in 100m at 2019 world championships

• That season, ~2500 men ran times to beat the female gold medalist

Male vs. Female: Voice types

• Female singers:

  • Pitch ~160-300 Hertz

  • Soprano, mezzo-soprano, contralto

• Male singers:

  • Pitch ~60-180 Hertz

  • Tenor, baritone, bass

Behaviour and Testosterone

• Classic behavioural change with anabolic steroids → ↑ increased aggression

• However, anywhere from ~20% of normal levels to 2x normal is largely unpredictive of anything

  • ↓ testosterone to 0 → ↓ aggression (seen with animal castration)

  • “Roid rage” → test levels 4x+ higher

• Obviously many factors contributing to predisposition for aggressive behaviour:

  • Nature: brain structures (amygdala, etc)

  • Nurture: traumatic incidents in childhood, etc.

Behaviour and Biological Sex

• 150 studies of over 100,000 subjects

• Different categories of risk taking behaviour were evaluated and men finished ahead of women in 14/16 categories

  • One of the ties → smoking

• “Men are by far the more reckless sex” - ↑ recklessness and risk-taking behaviour

Behaviour & Biological Sex: Crime

• Men commit the overwhelming majority of violent crimes

• Firearms: men and boys are 2/3 victims and 9/10 people accused of firearm related violence

• Executions: 883 total, 13 women (1.5%)

  • Held up across multiple countries (nurture may not play as much of a role)

Behaviour & Biological Sex: Jobs

• Men die in occupational jobs far more than women

• Dominate top 20 most dangerous jobs in %

Behaviour & Biological Sex: Darwin awards

• Award given for dying the stupidest death

• Men are way more likely to receive this award (90%)

  • Women: 10%

Shark Attacks

• More than 80% of recorded shark bites in history happened to men

• According to recent data, more females are being bitten

  • Attributable to more women gaining equality and engaging in water sports

Cross of Valour/Star of Courage

• Two highest honours for bravery available for Canadian citizens

• Since 1972:

  • 484 recipients: 437 men, 47 women

  • Risk-taking can sometimes be beneficial (saving someone who fell in ice, running into burning building)

Behaviour: control for environment?

• Sampled ~80,000 people from 76 countries

  • 6 fundamental preferences

• Men were more likely to be risk-taking and more willing to punish negative actions

  • Differences become more pronounced in countries with increased levels of economic development/gender equality

Marathon Participation in 2019

• Large difference between male and female participation

  • 2/3 male, 1/3 female across Canada

Participation in Shorter Races?

• Way more women competed in Toronto 10k than men

• Shorter distance → ↑ women

3 pillars of evolutionary biology

1. Variability

2. Heritability

3. Differential reproductive success

Variability

• Not all members of a species are exactly the same

• They differ across many traits

  • Height, intelligence, etc.

Heritability

• Some portion of some traits are attributable to genes passed down from parents to offsprint

Differential reproductive success

• Not everyone has the same number of kids

  • ↑ # of kids → ↑ success (genes passed down)

How much can an individual procreate?

• Genghis Khan

  • DNA is still seen today (he lived 1000s of years ago)

  • Was a conqueror - lots of free time

• Some lady from 1400s

  • 69 kids (27 births) → 16 pairs of twins, 7 sets of triplets, 4 sets of quadruplets

  • Could not do anything else in life

Cost of Getting Genes into Next Generation

• Males:

  • Voluntary release sperm

  • No cost for pregnancy, lactation or childbirth

• Females:

  • 1 egg cell/28 days from menarche-menopause

  • Need 72800 calories, extra folic acid, iron, physical illness during pregancy

  • Need extra calories and vitamins during lactation

  • Potential death during childbirth

Modern Pregnancy-Related Deaths (USA)

• CDC data with PMSS for 2011-15 analyzed

  • ~700 women die from pregnancy-related complications in US every year

  • Translates to 17.2 deaths per 100k live births

  • Significant racial/ethnic disparities

    • ↑ for African American, Native American and Alaska native women

How many mammals are there?

• >6000 species of mammals

  • Not all live in “social groups”

• Authors analyzed 76 social species to determine which sex occupied “leadership role”

  • Females: leaders in 8 species (10.5%)

Challenge Hypothesis

• Developed in 1990

• Explained 3 seasonal fluctuations in testosterone observed in birds:

  • Levels lowest in non-breeding season

  • Testosterone increases at start of breeding season

  • Physiological max testosterone level reached when male-male competitive interactions happened

• Subsequent meta-analysis in human males → simulated competitions influence testosterone

  • Winning → ↑ testosterone

Differences in Toy Preference

• Meta-analysis in 16 studies from multiple locations

• Children overwhelmingly chose to play with toys typed to their gender

  • Meta-regression showed no significant effect of presence of an adult, study context, geographical location of study, publication date, child’s age, inclusion of gender neutral toys

• Compared interactions of 34 rhesus monkeys with human wheeled toys and plush toys

  • Male monkeys showed consistent, stronger preference for wheeled toys

  • Female monkeys showed greater variability in preferences

  • Nature seems to have a greater effect

Sexual Dimorphism

• Condition where 2 sexes of the same species exhibit different characteristics

  • Ie. size, colour, markings, other features

• Usually resulting from sexual selection

• Dimorphism often allows males to fight for females

  • Ex. elephant seals: giant nose

Hyenas: Exception

• Hyena procreation is bizarre and dictated by the female

• Fallacy of logic → exception proving the rule

Law of parsimony

• Principle that the simplest explanation of an extent or observation is the preferred explanation

  • “if you hear hoofbeats, think horses, not zebras”

Comparing Male vs. Female athletes

• Christine Sinclair: greatest Canadian football player of all time

• But… overlooked due to being a woman

  • People think Alphonso Davies is greater simply because he is a man

• It is not productive to compare male vs. female athletes

Representation in Healthcare

• Important to discuss biological sex differences for purpose of representation

  • Women are not just smaller men → research is not translatable

  • Studying women is crucial for diagnosis and treatment → pathologies differ (ex. heart attack)

Diseasing with Differing Prevalence in Men vs. Women

• Some are obvious:

  • Organ specific cancers (breast, ovarian, prostate)

  • Disorders associated with menstrual cycle

• Others are less obvious:

  • ADHD prevalence greated in males

  • 1/5 and 1/3 women break bone due to osteoporosis in their lifetime

  • Nearly 60% of all people with arthritis are women

  • 75-90% of people with fibromyalgia are women

  • Global incidence of depression (2010) was 5.5% for women and 3.2% for men

    • 1.7x more common in women

  • Other types of “pain” disorders are more common in women

    • Ex. migraines, IBS, anxiety, UTIs

Life Expectancy Trends

• Women live longer than men

“Straw Man” Fallacy of Logic

• Misrepresenting, exaggerating, or just completely fabricating your opponent’s arguments, usually as something extreme or easy to argue about

  • Change subject and make a statement that is hard to argue

Transgender

• Describes a psychological identification with the gender that is different from the person’s gender as assigned at birth

Intersex

• Refers to persons born with congenital conditions in which development of chromosomal gonadal or anatomic sex is atypical

Timeline of gender testing in sports

• 1928: women are allowed to compete in track and field at Olympics

  • Occasional spot checks for external genitalia → obviously discouraged women from signing up

• 1968: advent of chromosome testing

  • Males = XY, females = XX

  • Problem is that human chromosomes don’t always divide into binary groups (ie. intersex)

• 2011: IAAF implements regulations based on hyperandrogenism with the key metric being functional testosterone

  • Measure test levels to distinguish M vs. F

Consensus meeting on sex reassignment and hyperandrogenism (2015)

1. Those who transition from female to male are eligible to compete in the male category without restriction

2. Those who transition from male to female are eligible to compete in the female category under the following conditions

   • Athlete has declared that her gender identity is female (min. 4 years)

   • Total serum test level has been <10 nmol/L for at least 12 months prior to first competition

   • Total serum test level stays below <10 nmol/L throughout competition

   • Compliance with these conditions may be monitored by testing

Eligibility regulations for female classification (2018)

• Any athlete with difference in sexual development (DSD) must meet the following criteria to be eligible to compete in restricted events (400m-mile) in an international competition:

  1. Must be recognized by law as female or intersex

  2. Must reduce her blood test level to <5 nmol/L for a continuous period of 6+ months

  3. Must maintain blood testosterone <5 nmol/L continuously (whether in/out of competition)

• REDUCED cutoffs

Why pick on testosterone?

• “To the best of our knowledge, there is no other genetic or biological trait encountered in female athletics that confers such a huge performance advantage”

  • Which is why FTM athletes compete with no restrictions, while MTF face pitfalls

Do Serum Androgens Influence Athletic Performance?

• 2127 observations of competition best performances and serum androgen concentrations

  • Obtained in 2011-2013 IAAF World Championships

• Argument against allowing high T women:

  • Women in lowest free test group performed significantly worse than women in highest group in 400m, 400m hurdles, 800m, hammer throw, pole vault

• Argument in favour of allowing high T women:

  • Many other events showed no difference

  • This pattern was not found in any of the male athletic events

• 8 trans female distance runners

  • 7/8 runners experienced significant slowing of race times from 5k-marathon distance

  • The 1 runner improving also lost 20 pounds and significantly increased training

Serum Androgens and Performance: USAF

• 29 trans men and 46 trans women who started gender affirming hormones while in the US Air Force

• Compare pre- and post-hormone fitness results of athletes with average performance of all men and women under age of 30 in USAF between 2004-24

• Conclusions:

  • Prior to hormones, trans women performed 31% more pushups, 15% more situps and ran 21% faster (↑ performance)

  • After two years of taking hormones, pushup and situp differences disappeared but trans women were still 12% faster (still slight ↑ performance despite ↓ test levels)