Name: 雌激素與自閉症之間的意外聯繫｜科學秀新聞 (The Unexpected Connection Between Estrogen and Autism | SciShow News)
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Scientists have been studying autism spectrum disorder for the better part of a century,

and yet, there's one thing they can't seem to figure out:

why the brains of people with autism develop differently.

some researchers have long suspected that testosterone levels in the womb are the key.

The only problem is, their evidence has come up short.

Turns out they might have been looking at the wrong hormones.

Just this week, a team of scientists at the University of Cambridge

and the State Serum Institute in Denmark announced that they've identified a link between autism

And while might sound like the complete opposite of what you'd expect for something more

it actually lines up with our understanding of autism better than you'd think.

Autism spectrum disorder affects about every one in 59 children,

but even after correcting for underdiagnosis and misdiagnosis,

it's roughly three times more likely in boys than in girls.

Girls with autism also generally have fewer autistic traits than boys.

And all that may imply that there's some kind of connection between autism

and the physiological differences that generally come with a Y chromosome.

Some have even suggested that autism is basically what happens

when you take typically male neurological traits and dial them up to 11.

This is what's known as the “extreme male brain theory” of autism.

Now, it's important to note that this doesn't mean that autistic people are super masculine

it just means that they have more of the traits that you see more frequently,

And the differences we're talking about are very small.

Studies consistently show that men and women are more psychologically similar than they

on average are more common or more pronounced in the brains of people with a Y chromosome

And it does seem like these traits are amplified in people with autism.

the brains of men tend to have weaker connectivity in the brain's default mode network.

That's a group of brain regions that's most active when you're not focused on the

And it turns out that both men and women with autism have even lower connectivity in this

Because there does seem to be some merit to this extreme male brain idea,

researchers have suggested that the biological pathways involved in the development of typically

masculine traits might be at the root of autism.

And that all traces back to fetal sex differentiation:

the biological cues that lead to the development

of typically masculine or feminine traits.

researchers have begun to look for clues to autism in fetal development

and the conditions fetuses experience in-utero.

the hormones involved in typically male traits—

might be to blame, which makes intuitive sense.

The thing is, studies on prenatal testosterone levels alone—

which is arguably the most important androgen—

have found no relationship between it and autistic features.

Cambridge and Danish researchers found elevated levels of several sex hormones in the amniotic

And while that did include testosterone and another androgen,

which got the researchers thinking maybe they needed to widen their scope.

Estrogen actually refers to a group of hormones

which includes estriol, estradiol, estrone, and estetrol—

none of which were tested in that 2015 study.

And these so-called “female” hormones are very important

It helps to form and prune neurons and synapses,

and it regulates the activity of the neurotransmitter GABA.

synapse and neuron formation and GABA regulation are all atypical.

So it might make sense that estrogen levels in the womb

could play a role in the development of autism, too.

To find out, those same researchers returned to the amniotic fluid samples they used in

These initially came from The Danish Historic Birth Cohort:

a set of biological samples from more than a hundred thousand pregnant people collected

who were followed up with to monitor the children's health over time,

including whether they were diagnosed with autism.

The researchers ended up with amniotic fluid samples from 98 males with autism and 177

They then analyzed the samples for various forms of estrogen.

they found that elevated levels of estradiol, estriol, and estrone

were all associated with an autism diagnosis.

a rise in this hormone from the 25th to the 75th percentile came with an almost 50% increase

That's a lot more of an effect than has ever been seen with androgens.

Now, it may sound strange that estrogen, of all things,

could lead to a so-called “extreme male brain.”

But remember, estrogens do a lot of different things to a developing fetus,

depending on the tissues and the development period.

And they're not exclusively a female thing.

In fact, maternal estrogen levels are higher throughout pregnancy