As we are in the midst of the Holiday Season it's a good time to review some of the basic biological differences between men and women, and why they matter to medicine.

So, a very short 🧵on Sex, Stress and the Holidays.
The time that it takes for food to work its way through the gut is referred to as 'transit time'.

And this digestive speed differs by sex: faster in men, slower in women.

Why does sex matter? Because the absorption of many medications are influenced by transit time.
Alcohol consumption by fruit flies has markedly different physiological effects, drink for drink, depending if the fly is male or female.

In humans, this is the case even when you control for body fat composition and weight.

The figure below is what happens when flies drink.
Selective Serotonin Reuptake Inhibitors or SSRIs are a class of drugs (the most famous example being Prozac) which are used to treat depression, anxiety and mood disorders.

Even when you control for other factors, some of the SSRIs work much better for women than men.
In many cultures presents are exchanged at this time of year.

Are you male and thinking of buying a gift for your father? A reminder that you were 'gifted' with approximately 900 less genes from your father than your mother.

Females receive about the same amount from both.

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More from @sharonmoalem

26 Jan
Viruses love to mutate. And some viruses mutate more than others. The biggest challenge for our immune system and any vaccination strategy that uses it, are viral mutations.

So why did the polio vaccine work while most of the #COVID19 vaccines will not?

A short thread.

1/5
The development of the polio vaccine was heralded as a major public health triumph. And it really was.

But did we just get lucky?

You see, polio has a higher mutation rate than HIV (which there's no current vaccine for). So why didn't polio escape vaccine?

2/5
Because being good at mutating is one thing. And being able to out-mutate and escape vaccine is another. Being able to do both and still be a functional virus that can successfully infect a host is something altogether different.

3/5
Read 5 tweets
9 Jan
Why do bartenders have the most experience dealing with the differences in how women and men metabolize a drug?

Because alcohol.

A short thread on how medicine doesn't consider drug metabolism differences between the biological sexes.

1/5 Image
We used to think that differences in alcohol tolerance between M + F was only due to any differences in weight/fat.

But that's not the whole story.

Even when sexes are matched for weight, there is a marked discrepancy in which sex metabolizes alcohol faster, M>F.

2/5 Image
Women don't have the same level of activity of alcohol dehydrogenase, an enzyme which helps break down alcohol in the body.

And other enzymes that break down prescription drugs may also be less active in women, making them more likely to experience adverse side effects. Image
Read 7 tweets
1 Jan
Why are 95% of 'supercentenarians' (those who are 110 years of age and beyond) women?

Because biological sex.

And so, a short thread on sex and longevity.

1/7 Image
From the beginning of life more girls make it their first birthday almost everywhere around the world, according to the @WHO. Girls have lower rates of prematurity and fewer complications after birth.

Females don't wait long to begin to dominate when it comes to survival.

2/7 Image
Women are naturally resistant to cancer.

Throughout life, women not only develop less cancers in organs and tissues that they share with men, but even when they do, they're much more likely to survive them.

Note: this is the case even when we adjust for behavior.

3/7 Image
Read 8 tweets
21 Dec 20
The evolutionary arms race will never really end between microbes and humans. They (microbes) have as much to lose as we do if it does.
Microbes are responsible for some of the most profound differences between humans which we can still observe even today. This has been true since the first human.
Some humans are born able to naturally resist HIV. This is thanks to them inheriting a small but significant genetic change - CCR5 delta 32.

Most humans do not have CCR5 delta 32.

HIV takes advantage of this fact.
Read 6 tweets
12 Mar 20
It is an unwritten law of biology that human males are much more fragile and lack the stamina and resilience in the face of biological challenges such as cancer and infections.
Notwithstanding their greater muscle mass and physical strength, males are the XY heterogametic genetically weaker sex
The cost that XX females pay for their immunological vigor is a much higher preponderance towards developing autoimmunity.
Read 7 tweets

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