Every new child has a few surprises, but imagine bringing home an adopted baby to find he was born with a super strength beyond the biological limits of most humans.
At 5 months old, Liam Hoekstra of Grand Rapids, Mich., started doing an expert gymnast move called the iron cross. By 8 months old, Liam could do a pull-up and by 9 months, he could climb up and down stairs.
"I would hold him up by his hands and he would lift himself into an iron cross. That's when we were like, 'whoa, this is weird,'" Liam's mother, Dana Hoekstra told The Associated Press.
Soon, the family thought to take him to specialists, who diagnosed Liam with a rare condition loosely called myostatin-related muscle hypertrophy, according to reporting by the AP.
The condition is so rare, only a few similar cases have been documented in medical literature. Hoekstra declined to do more interviews with ABCNews.com, saying she hoped to get her son out of the limelight for a while.
Many substances in the body can control muscle growth, but in 1997, Johns Hopkins University researchers discovered a gene and a protein called myostatin, first in mice, then in a breed of muscular cattle called the Belgian Blue.
"It's one of the reasons why I don't look like Arnold Schwarzenegger," said Dominic Wells, a professor who studies myostatin at Imperial College London.
Wells explained that virtually every animal on Earth has a gene that produces a muscle growth-inhibiting protein called myostatin. High levels of myostatin make it hard for the body to build muscle, and low levels of myostatin allow muscle to grow.
After the mice and cattle discovery, scientists found natural mutations in some dogs and sheep, but never in a human until 2004.
"In 2004 we reported on this German child, and to my knowledge, that is the only clear-cut documented case of a mutation in a human," said Dr. Se-Jin Lee, professor of molecular biology and genetics at Johns Hopkins University School of Medicine in Baltimore.
The German boy was born with a defective myostatin gene and showed super strength that surpassed Liam's, who had a functional gene but an unspecified difficulty regulating myostatin.
Lee said he has heard of several attempts to use antibodies or other means to block the myostatin gene for the purpose of treating muscular dystrophy.
But of the research he's followed -- research at the Amgen biotech company in California, Johns Hopkins University and the Acceleron company in Massachusetts -- Lee said he has yet to hear of a success.
"It hasn't been documented that if you give a myostatin blocker that you could get muscle to grow," he said.
"At the moment, there really isn't anything out there that alters myostatin levels other than exercise," Wells said. "It costs energy to keep the muscle alive; the body is very nicely tuned, so if you don't need the muscle, you lose it."
Since Liam's muscles don't see the effect of myostatin, he has a monstrous appetite.
"He's hungry for a full meal about every hour because of his rapid metabolism," Dana Hoekstra told the AP. "He's already eating me out of house and home."