She's being described as the "20-year-old toddler" who hasn't grown for the past 15 years. Brooke Greenberg is said to be the only one in the world with her condition.

Greenberg was featured on the "Katie" daytime talk show with Katie Couric this week. She's only 16 pounds and 20 inches long but she's 20 years old.

She grew normally until the age of around four. That's when she stopped, her father, Howard Greenberg, said.

Both Howard and his wife, Melanie, noticed that their third child wasn't hitting the milestones that children normally hit as they grow.

"She didn't grow so a lot of it was blamed on she doesn't have enough energy, she's not big enough to hit those milestone," Melanie said on the "Katie" show.

Howard Greenberg gave her a special growth hormone that the doctor provided every day for six to seven months. But it had no effect.

Follow us

The doctor told Howard that if he had taken that amount of growth hormones, he would be the size of an NFL football player.

"It did nothing to Brooke," Howard said. His daughter has been at the same weight for the past 15 years. Experts haven't been able to diagnose her condition.

Though challenging, the Greenbergs say it has gotten a little bit easier to take care of her.

"She's our child. Hopefully anybody in our situation would do the same," said Howard. "She comes first; we try to do what we can to make her happy."

"She loves to be held," Melanie Greenberg said.

Though they initially wanted to have a diagnosis for Brooke's condition so they could help her, Howard now says she doesn't need to be "fixed."

"Now I don't know who's normal – her or us. I have a hard time with that because I think she's normal. She's not broken; there's nothing to be fixed."

Brooke Greenberg has a younger sister, 17, who has grown normally.