Hi listeners, Benjamin from the Nature podcast here. This week we've got a podcast extra for you.

We couldn't include it in the regular show because the paper it's based on was released on a Thursday.

But we didn't want you to miss out, so here's reporter Ali Jennings with the story.

Medicine has made huge advances over the last century, but there have been times when novel treatments

have done harm as well as good. One such treatment is the subject of a new paper, now published

in nature. It involves giving human growth hormone to persons of short stature to help stimulate their growth.

Researchers from the Pryon Institute at University College London

suspected that some early batches of this growth hormone might be linked to the build-up in the

brain of a protein called amyloid beta. Build-up of amyloid beta is bad news. It's one of the

hallmarks of Alzheimer's disease. The researchers wanted to see if these batches of growth hormone

really were causing the accumulation of amyloid beta in the brain. So we used genetically modified mice, and we injected these mice with material from a number

of these files of growth hormone, and we found that the animals did indeed then develop

amyloid beta pathology.

This is John Collins, who led the research.

So that was a very striking finding and obviously also a very worrying one in terms of its

implications.

But to understand the implications properly, you need to know the whole story, because this

paper is really the final chapter in a saga that started some years ago.

Bear with me, I promise it's worth it. Back in the 1950s, doctors found a way of producing human growth hormone to help

treat persons of short stature. They harvested it from the pituitary glands of human corpses.

But in 1985, the treatment had to be stopped.

What became apparent in around 1985 was that some of these batches of hormone had been

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