The hormone therapy has now been stopped, but the proteins can also be carried on surgical instruments, say researchers from University College London.
They can't be sure that the growth hormones cause Alzheimer's disease, but they are concerned that they contain seeds that cause amyloid pathology in the brain, one of the chief characteristics of the disease.
The same researchers found a similar link to CJD in a study they carried out in 2015. "We found that some who developed CJD many years after treatment as children with cadaver-derived (from dead bodies) human pituitary growth hormone also had deposits in the brain of a type of protein characteristic of Alzheimer's," said researcher Prof John Collinge.
The hormone treatment was stopped in 1985, but the researchers fear the same proteins could also be carried by contaminated surgical instruments, especially those used for brain surgery, although they say they "cannot yet confirm whether medical or surgical procedures have ever caused Alzheimer's disease itself."