- And here we go.

Puberty.

- [Alok] Puberty 101.

- [Bethany] Puberty 101.

- Let's take it back to those early, awkward years.

- I don't know if it was awkward, as much as just I was awkward.

- Everyone's different.

- And it's fine.

- And it's fine.

(cheerful music) - The process of puberty is going from childhood to becoming a reproductive being.

- [Alok] That's what it is.

- How does it all start?

You're just going along, minding your business, having your friends, reading your books, and then all of a sudden, Like, what?

- Start yodeling?

- I started yodeling!

You didn't?

- So when we're born, the reproductive axis, which is this fancy way of saying, the parts of your brain which control all the hormones needed for puberty, that axis is active for a very short period, and then it's suppressed.

And then, for a multitude of different reasons we don't fully understand, the axis comes alive later and starts puberty.

- [Bethany] It just takes a long nap.

- It takes a long nap!

- It's like, "Hey, what we doin', what we doin'?

Oh, nothing?

Breastfeeding?

Okay."

- Here's essentially what happens.

There's a lot of different chemical reactions and hormones being thrown around the body.

Remember, hormones - very, very complex topic, but these are essentially chemical messengers that run around your body and basically tell different parts of your body to do things.

And one thing that happens is the adrenal glands start to secrete hormones, adrenal androgens.

This process, which we call adrenarche - [Bethany] Adrenarche.

- [Alok] And this is responsible for underarm hair, pubic hair, skin oiliness, all that stuff, that body odor.

- Adrenarche.

Sounds like anarchy.

That's what it feels like kinda.

Yeah, like I was just chilling, reading my books, reading my Kafka.

And all of a sudden, blah!

- Is Kafka good puberty reading?

We suspect that the body has its own internal rhythm for triggering puberty.

- So we know the popular signs of puberty, but how does it happen?

- I like the fact that you're calling it popular, because it's nothing to be ashamed of.

- It's not!

- The hypothalamus, up here in the brain, (whistling) the mothership will go from a steady release of something called gonadotropin-releasing hormone, or GnRH to releasing it in pulses, which then tells your pituitary gland to release two of the major players in puberty, LH, or luteinizing hormone, and FSH, follicle-stimulating hormone.

And this is where everything else happens and where the cascade starts.

- The cascade being?

- The transition to being a sexually mature organism capable for reproduction.

- Woo.

Clearly, you know, there are different body parts and such involved here.

Does that inform the hormones?

Does that inform what the hormones do, like, how the changes happen?

- We do have different body parts.

But let me take a minute here and say that in addition to girls parts or boy parts, there are also people who have different parts, or intermediate parts.

People who don't fit within a traditional binary gender system of male or female.

There are people who are trans, or people who don't have a gender.

But when it comes to puberty, we're just talking about a biological process.

So here's how it usually operates for people who have ovaries and people who have testicles.

So luteinizing hormone and follicle-stimulating hormone, LH and FSH, are gonna do different things depending on if you have ovaries or if you have testicles because there's different sexual maturation processes.

So let's start with girls.

Around the age of 8 to 13, LH and FSH are gonna head down to the ovaries.

- That sounds like a joke.

LH and FSH headed down to the ovaries.

- [Alok] They're gonna cause maturation of the ovaries, the release of eggs, and the rise of certain hormones like estrogen.

Still a funny joke?

- Yeah, very funny.

Estrogens!

(laughter) - [Alok] This influx in hormones may then go and influence thelarche - [Bethany] Thelarche.

- which is the development of small, firm, tender breast buds.

So it's basically early breast development.

- [Bethany] Okay.

- After this, we start to really see a growth spurt.

We'll also see the redistribution of fat in girls around their hips, their butts, and their breasts.

And at this time, there's also enlargement of the uterus, and further development of the vaginal mucosa.

And then, after this, we have menarche, or the first period.

And this kind of completes puberty.

- What about boys?

- Boys a little different.

We're gonna do that in a second cut, because I'm going to review my notes real quick.

- Okay.

- What about boys?

- What about boys?

- Well, we have something very special called testicles.

I was too enthusiastic about that.

But basically, LH and FSH, our two puberty hormones, travel down to the testes, where they're going to stimulate the production of sperm and testosterone.

Now, around this time, boys will also see a growth spurt, which comes a couple years later than girls.

- [Bethany] Okay.

- Sometime around age 10 to 16.

- This is true.

I was taller than every boy I knew, until I was about 17 or so.

- But also, there are some body changes in them as well.

Boys' shoulders start to broaden, they develop more muscle, they put on weight.

Also at this time, guys will start to develop facial hair, which is always a really fun one to deal with.

I cut my face plenty of times in junior high.

And the thing that everyone loves to do impressions of is boys' voices start to crack and squeak.

And what's happening is the vocal cords start to grow longer, and the larynx, or the voice box, starts to get bigger.

- Does that have to do with the... - Yeah, it pushes it pushes out a piece of tissue, which is why boys usually have an Adam's apple.

Some boys during this hormone influx can develop something called gynecomastia.

Or breast buds.

Nothing to worry about, but it's essentially a small amount of breast tissue, under the nipples obviously, can be tender, but it goes away after a few months.

As the testicles get larger boys enter spermarche, the development of sperm.

There's also the enlargement of the penis as well.

This will lead to more erections.

This'll even lead to ejaculation, which may happen from masturbation or from a wet dream.

There, I said it.

- What about kids who don't hit those timeframes?

- So there's variation, but there's also what we call delayed puberty.

Sometimes it's no big deal and everything's gonna be okay.

Your child's going to develop without any issue.

Other times, it might be related to an underlying medical condition, poor nutrition, or, for some, it could be related to intense physical training for something like track, dancing, or gymnastics.

Don't fret, chat with your doctor, and if you can chat with an endocrinologist, a specialist at dealing with hormones.

- Perfect.

- Funny story.

- Oh?

- Everyone remembers AOL Instant Messenger, rest in peace.

I used to talk on that thing until really late at night when I was a teenager and my mom says that because of that lack of sleep, I didn't get growth hormone, which is why I'm short.

So, she blames AOL Instant Messenger for my height.

Do you want to see what happens when I'm not on these blocks?

(laughter) You know?