A study shows that people who received growth hormones from deceased people may later develop dementia. However, researchers warn against drawing a connection from this. There is no evidence that Alzheimer’s disease is transmitted by other means.
Until 1985, it was common practice to give hormones from the pituitary glands of deceased children to minors with growth disorders. The procedure came to an abrupt end when several of those treated later developed the fatal Creutzfeld-Jakob disease (CJD). Data from a team led by John Collinge from University College London in Great Britain suggests that the preparations at that time also promoted the development of Alzheimer’s disease: In rare cases, such pathological proteins could pass from one person to the next and lay the seeds for the form of dementia .
Five of eight patients examined developed early dementia
The experts examined eight patients who had received human growth hormones from the pituitary glands of deceased people during their childhood and adolescence. None of the participants suffered from CJD, but five of them showed clear signs of early-onset dementia and three had already been diagnosed with Alzheimer’s. Her symptoms had begun between the ages of 38 and 55. Of the remaining three, one person had mild cognitive impairment and another reported subjective mental problems.
Michael Beekes from the Robert Koch Institute in Berlin emphasizes to the Science Media Center that the study does not provide definitive neuropathological evidence of Alzheimer’s. However, the dementia diseases described would meet criteria for possible or probable forms of dementia of the Alzheimer type.
Three of the patients died during the study period. In one of them, the researchers detected the changes in the brain that are typical of Alzheimer’s, such as pathologically altered proteins, the beta-amyloid plaques. Some people develop Alzheimer’s symptoms particularly early because their amyloid gene contains certain mutations. To rule out this as a cause, the team examined the DNA of five test subjects. In none of them was there a change that could explain the early onset of dementia.
Expert: Conclusion is premature
Together, the data would suggest that the “germs” of the disease came from the brain extracts, the researchers conclude. They were therefore triggered by medical treatment and are therefore “iatrogenic”. The team also bases this judgment on previous work from their laboratory. These had detected amyloid deposits in the brains of people who had died of CJD and had once been treated with such extracts. In addition, experiments on mice demonstrated that the hormone preparations can trigger Alzheimer’s-typical processes in the rodents’ brains.
For Michael Beekes, however, the conclusion of iatrogenic Alzheimer’s disease is premature. He points out that two out of five patients had intellectual disabilities that increased their risk of developing early dementia. According to him, the new data provide evidence, but “further studies are desirable and necessary to check and, if necessary, support the far-reaching conclusions of the author team,” he adds.
No evidence of Alzheimer’s transmission via other routes
Between 1959 and 1985, around 27,000 people worldwide were treated with growth hormones obtained from the brains of deceased people. More than 200 of them developed CJD decades later. The discovery of the infectious proteins responsible for the disease, known as prions, earned Stanley Prusiner the 1997 Nobel Prize in Physiology or Medicine. The theory later emerged that Alzheimer’s could also be a prion disease. The new work supports the thesis, but still does not provide definitive proof.
The director of Alzheimer Research UK, Susan Kohlhaas, emphasizes that this route of Alzheimer’s transmission is the only one proven between humans. “There is no evidence that the disease can be transmitted through other routes such as surgical procedures,” she adds. And even the former risk is now zero: growth hormones have been produced biotechnologically since 1985. It is therefore impossible for Alzheimer’s germs to enter patients through hormone treatment.