Sunday, 21 October 2012

Growth Hormone and Creutzfeldt-Jakob Disease

It's National Pituitary Awareness Month, and I thought I should look for an interesting pituitary-related story to tell you all. As it turned out, I didn't have to look too far.

 Most people living in Britain today will remember the 1996 scare about "mad cow disease" or BSE (in cows the disease is called Bovine Spongiform Encephalopathy; when it's passed to humans it's variant Creutzfeldt-Jakob Disease or vCJD). It’s an extremely nasty degenerative brain disease, invariably fatal, and there was huge concern that beef contaminated with the disease had been in the food chain for some time. The illness can have a latency period of up to ten years before symptoms appear (or much, much longer according to some researchers), making it very difficult to trace the cause of the illness - and meaning that no-one has any definite idea how many people could have been infected. As of October 2009, there had been 166 identified cases of the illness in the UK.
Beware! This could be a mad cow.
It was a huge scandal in the UK, and I remember as a child being disappointed that I wasn't allowed to eat roast beef for what felt like a very long time - although admittedly this was less because I loved roast beef and more because I loved the accompanying Yorkshire pudding my mum served with it. But until recently I was not aware of a similar, albeit smaller-scale scandal that had occurred several years earlier.

Between 1963 and 1985, the US Government funded a programme which provided human growth hormone to children across the US who had failed to grow as expected. Failure to grow in children is sometimes due to a deficiency in growth hormone (surprise!) and this is still a treatment for children today; the difference is that these days it's made in a lab, while at that time it was extracted directly from the pituitary glands of human cadavers.

In 1985, it came to light that three of the people treated with human growth hormone (hGH) had gone on to die of Creutzfeldt-Jakob Disease. This is not the same illness as vCJD but it is similar - and it's very, very rare. The programme was stopped immediately and an investigation launched.

To date, 29 of the people treated with hGH in the US before 1977 have been diagnosed with CJD. That's about one in 95. The rates were much higher in some other countries; in the UK, which produced its own hGH, 64 of the 1849 people treated developed CJD; and in France, which also produced its own hGH, 119 out of 1700 patients went on to develop the disease. There have been cases reported in numerous other countries; the variation in incidence is likely due to the variation in the way the hormone was extracted and processed.

 The longest latency period recorded between someone receiving human Growth Hormone and going on to develop CJD is 38 years. The shortest period before developing symptoms with these kind of diseases is usually around 2 - 3 years. The symptoms progress very quickly, within just a few months, from dizziness, difficulty balancing and clumsiness to memory loss, seizures and death.

Most disturbingly of all, however, it later came to light that far more of the patients who had been treated with hGH went on to die of adrenal crisis - an entirely treatable problem - than of CJD. This problem isn't caused by the hGH treatment, it's simply the case that people with a growth hormone deficiency are more likely to also be deficient in other pituitary hormones, such as ACTH. Without sufficient ACTH, you will die - but safe and effective hormone replacement is available for people whose bodies don't produce enough ACTH. It's simply that their doctors failed to pick up on the fact that these people were ACTH-deficient until it was too late.

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