In humans the best known of the prion diseases is Creutzfeldt-Jakob Disease (CJD), also referred to as Mad Cow Disease. Although difficult to gauge, CJD reportedly affects around one in one million people per year.
In the U.S. this translates to 250 to 300 new cases per year. CJD is very difficult to diagnose leading to some discussion of the inaccuracy of the statistics available. Most of the cases are classical or sporadic CJD (sCJD), and these seem to appear from out of nowhere, without known cause.
The sporadic form accounts for approximately 85 percent of the cases, the familial form approximately 15 percent. There have also been a few cases which have occurred from contamination via medical procedures; this type is known as iatrogenic or Acquired CJD. Finally over the last few years, another type of Acquired CJD called variant (vCJD) has been identified in young people. CJD has been linked to ingestion of beef tainted with BSE (bovine spongiform encephalopathy), most cases have occurred in the UK. Sporadic CJD usually comes seemingly out of nowhere (http://www.cjdfoundation.org/Creutzfeldt-Jakob Disease Introduction).
In the past years there have been cases, in addition to one case reported in 1985, of Creutzfeldt-Jakob disease in recipients of human growth hormone in the UK. (http://qjmed.oxfordjournals.org/cgi/content/abstract/82/1/43).
Between the years of 1963 and 1985, hormones from the pituitary glands of cadavers were administered to infertile women and children with pituitary insufficiency. Most countries abandoned human-derived pituitary hormones in 1985 once the risk of CJD was recognized and a synthetic version was developed. Since the use of pituitary hormones from cadavers has mostly been eradicated, there has been a sharp decline in new cases of iatrogenic CJD from human-derived growth hormone.
Aimee Boyle is a regular contributor to EmpowHer.
http://memory.ucsf.edu/cjd/overview/intro/contagious/multiple/hormone