MONDAY, Feb. 4, 2013 (HealthDay News) -- A new analysis did not unearth any evidence to support concerns that neurological diseases such as Alzheimer's or Parkinson's might be infectious.
The finding stems from a review of Alzheimer's and Parkinson's disease risk among people who had received potentially contaminated human growth hormone from cadavers in the 1960s, '70s and '80s, as a treatment for stunted growth. Since then, a synthetic version of the growth hormone has been developed for these patients.
"Basically, the concern has been that the pathology of Alzheimer's or Parkinson's could be passed, or can move, from cell to cell," explained study author Dr. John Trojanowski, co-director of the Center for Neurodegenerative Disease Research and the Institute on Aging at the University of Pennsylvania School of Medicine, in Philadelphia.
"For example, there was recent evidence of cell-to-cell disease transfer among Parkinson's patients who underwent an experimental therapy in which nerve cells were transplanted into the brain," he said. "After 10 years, the grafted neurons developed Parkinson's pathology. In the same way, years back, cell-to-cell transmission was observed in so-called mad cow disease."
"But when we looked at a group of patients who had been injected with cadaver-derived pituitary extract decades ago, we found no individuals who had developed, 40 years later, either Alzheimer's or Parkinson's," Trojanowski added. "This suggests that there is no cell-to-cell transmission from human to human or from cell to cell."
Trojanowski and his colleagues reported the findings online Feb. 4 in the journal JAMA Neurology.
The U.S. National Institutes of Health notes that growth hormone deficiency results when the pituitary gland, which is situated at the base of the brain, fails to produce enough of the hormone, either as a result of congenital issues or following injury. The result can be an extremely slow rate of growth, resulting in shorter-than-average stature.
For affected patients, daily growth hormone injections are the standard of care. Prior to the development of synthetic growth hormone in 1985, this typically involved the use of hormones extracted from the pituitary glands of cadavers.
The authors said that between 1963 and 1985, roughly 7,700 American patients were treated with cadaver-derived growth hormone as part of a national program.
This practice was stopped, however, following the revelation that during the 1980s about 200 patients in the United States and abroad developed a rare and fatal brain disorder called Creutzfeldt-Jakob disease after having been injected with cadaver-derived growth hormone that was contaminated with abnormal proteins.
The new analysis revealed that, despite possible exposure to contaminated proteins, none of the patients who had undergone treatment with growth hormone from cadavers faced a higher risk for Alzheimer's, Parkinson's, frontotemporal lobar degeneration or amyotrophic lateral sclerosis -- also known as ALS or Lou Gehrig's disease.
"The bottom-line fear is that diseases such as Alzheimer's and Parkinson's might be transmissible and possibly infectious, which could be an issue beyond just human growth hormone patients," Trojanowski said. "Just think of all the organ transplants done in the U.S., and the risk of disease transmission if some of them use material that came from Alzheimer's or Parkinson's patients."
"This [new] study is not absolute proof that such transmissions can't happen," he acknowledged. "But, to my mind, it considerably allays such concerns."
Cheryl Grady, a senior scientist with the Rotman Research Institute in Toronto, agreed.
"I'm not at all surprised by these results," Grady said. "The only neuro-degenerative disease that I'm aware of as being transmittable is what people call mad cow disease, and one other disease called 'kuro,' which affected one cannibalistic tribe in New Guinea that used to eat their dead relatives."
"With so many transplants being done now, if something like this were a problem we would know about it," she added. "The issue with transplantation is not whether the new organ will make you sick, it's tissue rejection."
For more on growth hormone deficiency, visit the U.S. National Institutes of Health.