Growth hormone: What is it, who needs it?

You might imagine that growth hormone is a fairly straightforward sort of thing.  It does what it says on the tin.  Makes you grow.  If you’ve got enough you’ll grow, if you haven’t you won’t.  Like almost everything in nature of course that is only part of the story.

Growth hormone is made by the pituitary gland which sits on the undersurface of the brain behind your eyes.  It is very important in controlling growth in children particularly after the first couple of years of life.  It has many complex functions however, some of which are not completely understood.  It has an overall ‘anabolic’ effect, in other words it tends to make cells of the body grow.  So growth hormone has a positive effect not just on how tall people are but also on the strength of their bones and their muscle bulk and the size of their organs.  That’s why people who make too much growth hormone aren’t just tall, they have a whole host of other problems as well.  It’s also why some athletes have tried to use growth hormone as a performance enhancing drug.

So what has all this got to do with DSA?  There has been a lot of debate in the medical community over last 40 years about whether it makes sense to offer people who are of restricted growth extra growth hormone.  The huge majority of people who have a skeletal dysplasia produce normal amounts of growth hormone.  As you would expect there are some exceptions to this but they are very few and far between. People who do not make growth hormone or make it but can’t use it properly are of ‘proportionate’ short stature.  So people with achondroplasia or spondyloepiphyseal dysplasia or diastrophic dysplasia, make normal amounts of growth hormone.  In people with these conditions there are alterations in other proteins important in controlling the way that bones grow.

Some doctors have argued that even if people who are of restricted growth make normal amounts of growth hormone it might be possible to increase their height by giving them extra growth hormone, what is called ‘supra-physiological doses’.  In other words doses much higher than the body would normally produce itself.

In the mid 1990s a number of research studies were published which looked at the effects of giving extra growth hormone to children with achondroplasia.  Almost always these studies showed that in the first year or two of treatment there was an increase in the rate of growth.  The ‘growth velocity’.  As the studies progressed however and children were followed for 5 or 6 years it seemed that the initial effect was wearing off and that the rate of growth returned to the level that it was at before the growth hormone treatment was started.  There was also evidence from some of the studies that the bones of the spine grew more than the bones of the limbs suggesting that there might be an increase in the amount of disproportion between limb and spine growth if treatment continued for a long time.

So where are we now?  Many doctors believe that the most important thing is to see what the effect of growth hormone treatment is on the final height of children with achondroplasia.  The children who began treatment in the mid 1990s are now reaching final height and so there should be definitive answers to this in the next few years.

In the meantime most doctors who treat children with achondroplasia (and other forms of restricted growth) feel that growth hormone should only be used in the very rare cases where a child does not make any growth hormone of their own.  There are some children with achondroplasia receiving growth hormone but most of them are involved in one of the on going research studies. 

My personal view is that it is likely that the research studies will show that treating children with achondroplasia with growth hormone will increase their final adult height by perhaps one or two inches.  Treatment with growth hormone requires careful monitoring and the only way to give the drug is by daily injection.  For all of these reasons we do not currently recommend growth hormone treatment for children of restricted growth except in the very rare cases where the children do not make the hormone themselves.

Dr. Michael Wright

Newcastle upon Tyne

February 2011.