The stories of Laverne Cox and Caitlyn Jenner show how much the world has changed in recent years for those who are transgender. (Rich Fury/Invision for the Television Academy/AP Images; James White/E! Entertainment/NBC)

This doctor’s appointment was different for Tyler.

It would be more than the standard knee-tap, stethoscope, height/weight for an 8-year-old. It could determine whether it was time for the next big step.

Tyler is transgender.

And if the X-rays on his hands showed specific bone growth and mineral density, if the blood tests showed that the estrogen levels in his bloodstream were changing, if the soft tissue on his chest was growing, it would be time for the medical part of becoming Tyler.

He and his parents would have to decide whether to visit the doctor monthly for shots or use a surgical implant to inject drugs to stop puberty and keep his body from looking like that of a young woman.

“The implant. Definitely the implant,” the third-grader told the doctor.

And Tyler is certain about one other thing: “I’m a boy,” he says.

This is what he said when he was 2 and constantly combative in his girl name and girl clothes. And this is what he says now, in a new school with new friends and a little universe that sees him as he sees himself — as a boy.

And frankly, he doesn’t really want to talk about it anymore with you. Or me. Or anyone else in the binary-gender world.

And who could blame him? The road from Kathryn, his middle name at birth, to Tyler, his new, legal, middle name, was tough enough.

Not only for Tyler, who felt as though God made a mistake and people were wrong when they said “she” and he hated, hated, hated wearing a leotard to gymnastics.

But it was also rough for his parents — solid, pragmatic, religious schoolteachers — who had a mountain to climb when faced with the extraordinary challenge he presented to them.

This was before Caitlyn Jenner landed on the cover of Vanity Fair. Before Laverne Cox became a star for her portrayal of a transgender inmate on “Orange Is the New Black.” Before the White House hired an openly transgender staffer.

Three years ago, when transgender was still classified as a mental disorder in the American Psychiatric Association’s official diagnostic manual, Tyler’s parents were trying to figure out how to let the daughter they took home from the hospital become their only son.

I talked to Tyler’s mom through some of that process, with his father as he began to struggle with the life ahead for his younger child. I was with them the day Kathryn introduced herself as Tyler at Sunday school and on Tyler’s first day of kindergarten in a private school in Maryland that allowed him to enroll as a boy.

Tyler’s story challenged and inspired readers.

And in some ways, the world has changed dramatically since Jean, Tyler’s mom, found just one book to help learn about her transgender child.

“It feels like we were living in a completely different world three years ago,” she said.

They were constantly carrying a “safe file,” the folder full of paperwork, a psychiatrist’s diagnosis and her prescription for Tyler’s woes: “Let him live like a boy.” Because they never knew when an innocent moment — the bathroom at Ikea, the pool, the airport — could turn into a social services case.

But just last month, when Tyler was at the doctor, a clerk was confused by the gender on his insurance papers vs. his obviously boyish appearance.

Jean geared up for the fight. “He’s trans,” she began to explain.

“Oh, of course,” the clerk said, and went back to the paperwork.

“Really? That was it?” Jean marveled later. “I mean, wow! That wouldn’t have happened three years ago.”

So much changed that Tyler’s parents felt comfortable enough to leave the gentle, open-minded private school that was killing their finances but providing a haven for Tyler — and enroll him in public school.

And so far? It has been great.

Some of their biggest challenges, however, are ahead.

Medically, the puberty blockers Tyler is certain he wants appear to do no harm. Normal development can resume anytime in the tween’s life simply by stopping them.

Doctors who specialize in trans kids said the puberty blockers can be lifesaving, helping kids integrate during the toughest times of teendom. They also prevent costly and dangerous surgery later in adulthood, if gender reassignment surgery is the path taken.

Eventually, some older teens also begin taking hormones of the gender they identify with. So Tyler would get testosterone shots.

Those hormone injections, which typically begin at 16, would be a much tougher choice because they make the child sterile.

But Tyler and his parents are years from facing that decision. His X-rays and bloodwork show no signs of puberty, she said.

A small exhale. Still, after three years of living life completely and happily as a boy, Tyler’s family doesn’t see any other path for him.

At school, his new friends have no idea that he is transgender.

And this worries Jean. Because what about sleepovers and playdates and sleep-away summer camp?

“Fortunately, sleepovers aren’t as popular with boys at this age,” she exhaled. And if he does a sleepover, he’ll do it with friends from his old school, where he was known as the transgender kid.

At some point, she’ll have to face the request for a sleepover with someone who has no idea that he once had Kathryn in his name.

Sleepovers are one of the hot topics at the monthly transgender support group meetings that Tyler’s family hosts at their home. It’s a group that didn’t exist three years ago, and it’s growing every month.

At these meetings and at the transgender conventions and conferences and family weekends, Tyler is happy to talk about being transgender.

All the other kids are, and he is at home. An activist, even.

Once he’s back in the outside world, he is a boy.

And he would like it if we all just left it at that.