Why isn't the procedure used anymore, since they stopped using it before this was discovered?
>In the interim, scientists had discovered that that type of hormone treatment they got could unwittingly transfer bits of protein into recipients’ brains. In some cases, it had induced a fatal brain disease called Creutzfeldt-Jakob disease, or CJD — a finding that led to the banning of the procedure 40 years ago.
In other words, it gave people mad cow disease.
“Mad Cow Disease” specifically refers to the variant form that is said to have been caused by prions from infected animals turning up in beef products.
Though in fact all we know for sure about the link there is that it’s the same prion in the cattle and human cases; the suggestion that there’s a direct food chain connection is still only considered very likely, not proven.
Not just human growth hormone, also other hormones used to be derived this way, e.g. those used to induce ovulation in fertility treatment.
I know someone who received cadaver-derived fertility hormones in the 1980s. She has a small risk of developing CJD and dying from it. It hasn't happened yet, and probably never will, but no one can say for sure if she is infected. If you don't develop symptoms (some people are infected but never progress, others suddenly develop symptoms one day after decades of being asymptomatic), the only way to know for sure if you had it is at autopsy, through destructive testing of brain tissues.