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Purified growth hormone not tied to brain disease

By Genevra Pittman

NEW YORK (Reuters Health) - Short kids who were treated with human growth hormone after 1977 -- when scientists started purifying the hormone -- aren't as likely to get a devastating "mad cow"-like brain disease as a result, researchers said.

Previous studies had reported a disturbing pattern of cases of Creutzfeldt-Jakob disease (CJD) - which causes a fast decline in mental functioning, and generally death within a year -- in those who had taken the hormone in the 1960's and early-to-mid-1970's.

Even though the hormone is now made in the lab, where there's no risk of CJD contamination, the disease can take many years to show up. So people who got growth hormone injections in the more recent past -- as late as 1985, when it was still derived from human corpses, but purified -- might worry they are at risk for the brain disease.

The new findings should help ease that fear, researchers said.

"ALWAYS A SHORTAGE"

Scientists had tried for many years to treat people with dwarfism and other very short kids using hormones from animals -- but it never really worked.

Then, in the late 1950's, a researcher discovered that hormones taken from humans would help short kids grow taller, and soon a U.S. program was started to provide human growth hormone (hGH) to pediatric endocrinologists who were treating those kids.

"This was a very popular program. Many people pushed very hard to get their child the hormone, and there was always a shortage," said Dr. Lawrence Schonberger, one of the authors of a new study on hGH and brain disease from the Centers for Disease Control and Prevention in Atlanta.

As parents clamored to get their kids treated, there was a "great big push to get as much of the material as possible," he said, and that led to hormones from thousands of different cadavers being combined in a lab.

The growth hormone is produced by the pituitary gland, a pea-sized structure near the base of the brain.

"They would blend it all together, and they would come up with a product that could make these small children grow," he told Reuters Health.

Scientists knew that the hormones weren't that pure, and that there was some risk involved, said Susan Cohen, a journalist and the author of Normal at Any Cost: Tall Girls, Short Boys, and the Medical Industry's Quest to Manipulate Height. But, she said, "it was all about collecting more glands and squeezing as much growth hormone as you could out of the ones you had."

A PURER PRODUCT

Production of hGH switched in 1977 to the lab of Dr. Albert Parlow at Harbor-UCLA Medical Center in Torrance, California. Parlow says his lab instituted a very careful purification of the hormone -- unlike what scientists trying to mass-produce it had been doing before.

Eight years later, doctors began putting the pieces together from the cases of a few young patients previously treated with less-pure hGH who were diagnosed with CJD -- which generally strikes only in older adults. The disease is caused by a prion, a type of rogue protein that causes other proteins in the brain to fold in strange ways and lose their function.

Scientists figured the patients would have gotten the disease from hormones that were taken from the gland of someone who had also died of CJD, but weren't purified well enough in the lab.

Because the disease can take 20 years or longer to show up, "by the time it was discovered that CJD was occurring in kids treated with partially purified growth hormone, it was too late," Parlow told Reuters Health.

Cohen said it was because of Parlow's careful attention to purifying the hormone that more kids in the U.S. weren't infected with CJD between 1977 and 1985, when the hGH program was shut down. Kids in other countries weren't always so lucky.

"The French went on and ignored the warning and treated kids until 1988" with less-pure hormone, Cohen said. "Between '85 and '88, they had the largest (CJD) infection rate in the world."

All told, hGH has caused hundreds of deaths from CJD worldwide, researchers said, including outbreaks in the United Kingdom, France and New Zealand.

A "MUCH LOWER" RISK

Shortly after the production of hGH was halted in the U.S., a synthetic form of the hormone took its place -- one that couldn't transmit disease.

But the National Institutes of Health and other organizations that were originally involved in providing the growth hormone to kids wanted to see the story through.

Researchers have tracked everyone who received hGH through the national program to determine when they took the hormones (before or after scientists started purifying it), and whether they've been diagnosed with CJD.

That's the source of the findings of the current study, published in the Journal of Clinical Endocrinology & Metabolism. It includes 5,570 people who were treated in the U.S. between 1963 and 1985.

Of them, 22 people were diagnosed with the brain disease. All had started hGH treatment before 1977.

Because people who got the hormone later have had less time to be diagnosed, the study doesn't prove that no kids treated between 1977 and 1985 will get CJD -- but it does show they are much less likely to fall ill than those who were treated pre-1977.

"We now can tell you that whatever risk there was before, your risk is going to be much lower," said Schonberger.

"For those people who started treatment in '77 and after, it should be a big relief," Cohen added.

"These were people whose parents got letters for years ...from the National Institutes of Health saying, 'Were sorry to inform you that there's been more deaths,'" she said. "We had doctors say it was the worst experience of their lives, to sit down with their patient list and call them."

Other countries have compensated people who were given the impure growth hormone, and prosecuted some of the doctors that provided it. "The statement that kept coming out of these was, 'The lesson is we never know as much as we think we do,'" Cohen said.

"It has to be one of the most tragic episodes in medicine."

SOURCE: http://bit.ly/nSroDB Journal of Clinical Endocrinology & Metabolism, online August 3, 2011.

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