Growth - The Long Short Story

This has been written by a parent for parents who want to know AS MUCH AS POSSIBLE!

If your child is short should you be worried? Have you spoken to friends who have tried to re-assure you that you are being a little bit over anxious? 'Well, you're not very tall, are you?' ...'Well, what do you expect with all that he/she has been through?'.... 'I know someone who was very worried that their son was really small and then suddenly, whoosh, up he went and turned out to be taller than most of his friends!'

Boys are more likely to cause concern than girls, possibly because we don't worry about our daughters being short as much as we do our sons and perhaps because growth hormone deficiency does actually happen more often in boys than girls, it does sometimes come as part of the 22q11.2 deletion package of goodies!

The aim of this document is to outline the main elements of growth concerns in plain English. This is a very complicated issue as it's a matter of weighing up lots of factors. There is a glossary of terms at the end, so if something is new to you then have a look because once you get to grips with the 'technical terms' the fog often lifts by itself! Having said that you may need to read this all through several times... it has taken a long time to write!

This paper has been read and endorsed By Dr Jeremy Kirk, Consultant Endocrinologist at Birmingham Children's Hospital, which is one of the largest growth centres in the world (October 2004). It has also been read by Dr Tim Cheetham, Consultant Endocrinologist and Senior Lecturer in Endocrinology at University of Newcastle upon Tyne. We are very grateful to them for their time and valuable help.

Is your child actually short?

Get your red book and familiarise yourself with the growth charts (or give Max Appeal a tinkle if you can't find it/don't have one) and then follow the following steps:
1. Add Mum and Dad's height (in cms) and divide by 2 then, for boys add 7cm and for girls take away 7cm. This gives the 'Mid-Parental Height.' See where this is on the far right hand side of the chart.
2. Your child's final adult height could be 8.5cm above or below this, it's called the 'Target Centile Range'.
3. Measure your child. Sounds easy but make sure you have them standing up straight on a firm surface with heels against wall and feet flat on the floor (no tippy toes, no slumpy shoulders!), and that you measure from the top of the head at a 90 degree angle. The best way to do this is to use a cereal packet or book with the edge held vertically (not horizontally) against the wall. (If you are monitoring their growth then do it in the same spot at the same time of the day at the same time of the month with the same tape measure!)
4. Look on the left hand side of the chart for height and follow the bottom line across to your child's age and mark the spot where they meet.
5. Find the closest centile line to that and follow it up to the right of the chart.

Result:
Most (82%) children will fall between the 91st and 9th centile (this doesn't always mean that everything is okay but we'll come to that in a bit!). Also most of our children will have a target centile range that falls between the 91st and 9th centile.

If your child is in the shaded area at the bottom (below the 2nd centile) and you and your child's other biological parent are pretty average in height i.e. your child falls below their target centile range then there could be a problem.

Is being short just a cosmetic thing?

Having a little child can be cute and sweet. They can be babied and cuddled more. They get lots of attention for being so lovely. What happens when they are teenagers and adults?

Some might think that being short is no big deal. Being a bit short probably isn't... (being 5'3' myself) but being really short (perhaps more so for a man) such as to be 5 foot or under may not be a fun situation. Not everyone can be Frankie Dettori!

It is accepted that very short stature for adults is a quality of life issue. Not all very short adults will be adversely affected, but you won't know if your child will grow up to be in this group.

On the other hand your child may well have other issues that require medication and/or interventions of some sort or another, and perhaps this just isn't a priority for you. Ultimately the decision about its importance lies with you.

Are you still worried?

Shall we cut to the chase? The options for reasons for being short are:
1. Familial short stature
2. Constitutional delay
3. Something else!
4. Growth hormone deficiency

1. FAMILIAL SHORT STATURE

If you've plotted the charts as above then you will know if your child is taking after one of their parents. This might not be welcome news but it should be reassuring. However growth hormone deficiency can be inherited. You might want to ask to see a specialist just to be certain.

If your child has 'familial short stature' then they will achieve their genetic height potential however much you would have liked them to be taller and however much growth hormone they were given.

2. CONSTITUTIONAL DELAY

This refers to someone who is small for their age but catches up in a great big growth spurt after going into puberty a bit later than their peers (sometimes likened to tortoises). There are other people who are just the opposite; they mature very young (and are likened to hares), everyone knows the boy who started shaving when he was 12!

The Magic Foundation (in the US) set a guide of six considerations that need to be satisfied to PROVE a constitutional delay:
1. Normal birth weight and length
2. The rate of growth declining (falling off the chart) between the ages of 6 months and 2 yr 6 months usually to be below the 2nd centile. Measuring young children is notoriously difficult most will not have accurate length measurements in infancy.
3. Beyond the age of 2 yr 6 months to 3 years following one of the lines, that is a normal growth rate (velocity) but still short.
4. No evidence of a syndrome or other serious illness.
5. A bone age that is delayed but matches the height age (x-ray of left wrist assesses this).
6. A positive family history of at least one of the parents being short as a child, going through puberty late but having a normal (but perhaps a bit shorter than average) adult height.

The last item is not always seen (someone has to do it first!) but if ANY of the other five are not answered 'yes' then a diagnosis of constitutional delay should be questioned. Essentially points 1 to 5 should be ticked as 'yes' for a constitutional delay to be in the frame.

3. SOMETHING ELSE

Eeek! Like what?

Growth hormone deficiency is associated with 22q11.2 deletion, but you probably knew that already!

Being short is associated with some other genetic conditions such as Prader-Willi Syndrome (deletion of part of chromosome 15), Turner's syndrome in girls and Russell Silver Syndrome to name just a few. The first two are detectable by genetic testing. Russell Silver syndrome is a bit more tricky. It affects both boys and girls, they have features that may include sparing of head growth with body asymmetry (one side bigger than the other or shorter arms etc.)

Children who have had cancer or chronic renal failure can also be short. More specialised information on these is available from other sources than here. If your child has one of these conditions then there are guidelines about treatment from NICE (National Institute for Clinical Excellence) and you should see a paediatric endocrinologist.

Ifs and buts:

If your child has been very ill over a long period of time then they may also be small for their age. Usually an x-ray of their left wrist will establish that they have delay in their skeleton (bone age) that matches their delay in height. This means that when they do go through a long stretch of being well then they have a good chance of catching up, but this could also mask an endocrine problem.

A feeding problem might be asserted to have an impact on growth but it is generally agreed that in this country it would be extremely rare for a child not to have sufficient nutrition to grow normally. Children really do need to be starved for it to affect their height.

Having a complex heart defect on the other hand can affect height, but again if your child has growth failure and a heart defect then smoking gun evidence would point to that as the reason... this could be another red herring!

4. GROWTH HORMONE DEFICIENCY

NICE along with the British Society for Paediatric Endocrinology and Diabetes (BSPED) have laid out guidance on the testing and management of this. They are a bit complicated!

The basic criteria for seeing if growth hormone testing should be carried out:
1. Being below the 2nd centile (off the bottom of the chart to me and you and to an endocrinologist this is 2 HtSDS; 2 height standard deviations below the norm)
2. Growing less than 5 cm a year (poor growth velocity)... OR:
3. Normal growth velocity (following a centile line) till 2-3 years of age then tailing off and falling more than 2 centile lines in a year (they call this a reduction in growth velocity by 2 standard deviations)
4. Normal body proportions, sometimes with a younger looking face and 'puppy fat' around the waistline. They can also be a bit lethargic or lacking in energy.
5. Bone age delay.

Caveats: Not all of these must be present, an endocrinologist will weigh up the factors on an individual basis and decide whether to go ahead with growth hormone testing. You can ask your GP or paediatrician to refer you to an endocrinologist.

Essentially if a child is small but is following a centile line (i.e. a normal growth curve) then this is less likely to cause concern sufficient to trigger growth hormone testing than one who slips down the chart over a period of around a year or so.

So, if you and your child's father are very tall and your child was very tall (say on the 90th centile) but then just started to fall behind over a period of a year or so (but is still say only just under the 50th centile) then this should cause concern just the same as a child who is off the bottom of the chart but whose parents are average height.

Red Herrings:

The definitions and terms used by the NICE guidelines and the doctors are often difficult to follow for parents because of a reliance on 'standard deviations' rather than concrete measures such as cms or centile curves, where in fact here in the UK they are one and the same thing.

A delay in bone age is seen in children who have been chronically sick and in those with a constitutional delay and those with growth hormone deficiency! BUT it isn't always seen in growth hormone deficient children ... What it does do is help to eliminate those with familial short stature.

ISSUES SPECIFIC TO 22Q11.2 DELETION

People with 22q11.2 deletion are known to be associated with short stature. How many exactly is not known, but estimates vary between 39% and 75%. There is also the consideration that this is because of things like cardiac defects, feeding problems and immune deficiency that could affect growth in children.

A study of 40 children in Philadelphia found that there was a very high risk of growth factors in the blood (IGF-1 and IGFBP-3) being lower, for children with palatal abnormalities. It appears that having a heart defect will affect stature but is not more associated with GHD. They found that growth hormone treatment gave a 4 to 6 inch final height gain. (USA use imperial measures, ironically!)

It is their recommendation that ALL children with 22q11.2 deletion are screened for IGF-1 and IGFBP-3, but particularly those with palatal abnormalities.

What is growth hormone deficiency?

It means that the pea sized object at the back of the eyes and in front of the brain (called the pituitary gland) isn't doing its job properly, and there isn't enough growth hormone to support normal growth.

Growth Hormone Deficiency (GHD) can happen just on its own: this is Idiopathic (caused by no known reason) or Isolated Growth Hormone Deficiency (IGHD). 25% of children well under the 0.4th centile will have GHD, and out of these 50-70% have IGHD. Severe GHD is apparently easy to spot, but mild or moderate deficiency is a slippery character and this can cause lots of trips to various doctors and clinics over quite a long period of time. Many children with growth hormone deficiency don't have any particular features at all; they are just short.

If other pituitary hormones are affected then this is called Multiple Pituitary Hormone Deficiency, which is more complicated and you would need to have a good talk with your endocrinologist about this.

How do you get a diagnosis?

You will need to be seen by an endocrinologist but your paediatrician might want to conduct preliminary tests so that they can be certain of the need to refer onwards. They will probably want to do a blood test for Insulin like Growth Hormone Factor-1 (IGF-1) and other hormones and blood factors (to eliminate things like liver and kidney problems) and carry out a bone age x-ray.

A single blood test is next to useless for assessing levels of growth hormone, as it is produced in bursts throughout the day (pulsatile) and more than 50% of growth hormone is released within three hours after going to sleep.

On referral to the endocrinologist, they will probably want to measure your child over a period of time (on their absolutely deadly accurate measuring machines) to establish the growth velocity. These are called auxological tests. They may well want to repeat some tests like a bone age x-ray.

NB Being very short is accepted as affecting the quality of life for an adult, treatment has been established as being freely available for all people with GHD on the NHS, it is also far more effective the earlier it is begun. If you feel that your endocrinologist is sitting rubbing their chin for too long then it almost certainly isn't that they don't want to give out the treatment it might be that they just want to have the scales tipped firmly on 'certain' before they submit your child to growth hormone provocation testing....


What are the tests?

It is often referred to as the GH-IGF axis or radiological investigations, this is the relationship between Growth Hormone and Insulin-like Growth hormone Factor (IGF-1). IGF-1 is always present in the blood and is produced in response to Growth Hormone, and also nutrition (food). Low IGF-1 may indicate low GH.

They may well also look at Insulin-like Growth Factor Binding Protein 3 (IGFBP-3) but generally this is considered to be inferior for diagnostic purposes. By the way you can have normal IGF-1 and IGFBP-3 and still be GH deficient.

The 'gold standard' is: Growth Hormone Provocation Test.

There are a number of substances which stimulate growth hormone eg. glucagon, insulin, clonidine, arginine. The test must be done only by an endocrinology unit, it may be done once, or if there is a borderline result twice.

The format is essentially the same for both tests;
Nothing to eat or drink from midnight,
Go to the hospital day care unit first thing in the morning and have a cannula put in.
an initial blood sample is drawn
Then an injection is given, usually in the bum/leg for glucagon, and insulin is given through the cannula.
After this, samples are drawn from the cannula every half an hour for 3 hours.
Over this time your child will become grumpy, hot and perhaps sleepy (but must not go to sleep).
Once the last sample is taken your child will be allowed to wolf down a sandwich and crisps and chocolate and a nice drink! (Amazingly you almost certainly won't have to coax this meal down!!) They should then chill out at home for the rest of the day.

The test aims to stimulate production of growth hormone, just as happens naturally while you are asleep. The unfortunate side effect with insulin is the hypoglycaemic (low blood sugar) symptoms! These really are not very nice and the morning will probably seem like a real endurance test for you too! Your child will be monitored very closely by the experienced staff on the ward, who will probably do these tests one day every week. Low blood sugar can have dangerous side effects so you will be fully briefed by the staff on what to expect and what to look out for, which is why the test is not undertaken lightly.

You will be given leaflets on the previous visits to the clinic and it is best if you can try to prepare your child for this event as best you can. Cannulas are quite frightening both for those who have had them before and for those who haven't! For younger children we would recommend that you use pictures to show a 'timetable' for the day, you can cross them out as each one passes and they know what is going to happen next.

Results

The blood samples will be analysed to see what is the peak GH level. There is a fairly arbitrary level acknowledged amongst endocrinologists of 20(mU/l) (or around 7.5-10g/l) as being the minimum. If your child has a GH level below this then they will be offered growth hormone replacement therapy.

More ifs and buts:

NICE recommends that GH therapy should still be considered if GH levels are normal but IGF-1 is low.

Growth Hormone Replacement Therapy.
When this was first offered the growth hormone was taken from human pituitary glands, but in the 1980's recombinant growth hormone was created. This is a totally synthesised chemical and there are no risks of things like CJD. Other side effects are not widely noted, there are some but not many and they are not often reported. Your child may complain of headaches over a period of time and the treatment will be stopped for a time and then recommenced at a slightly lower dose. The treatment is very safe.

How do you give the therapy?

An injection into the fat under the skin usually every day. This will be until their skeleton is fully mature or that growth has slowed right down, i.e. until they are grown up. Don't reel in horror at the thought! It isn't as awful as it first seems!

If your child has a real problem with needles you can ask to see play therapists about a desensitisation programme. If you have an aversion to needles talk it through when the child isn't there, as we know children are telepathic and will suss this out as quick as a flash, so there is no point in trying to fudge it!

Also there are 'devices' that don't have needles! These are called transjectors and they use fine spray under very high pressure to force the hormone through the skin, (a bit like Dr McCoy on Star Trek). If you opt for a needle then this can come in a concealed 'pen type' device that works on the press of a button or just hides the needle from sight as it is inserted. Alternatively you can have a straight jab; old hand diabetics who have injected themselves a couple of times a day for many years might say 'keep it simple'!

In any case you will go to the hospital and see which device you can have. Some units allow you to choose from all the ranges that are available on the market, other units don't offer this sort of selection.

None are totally pain free (there is no point in beating around the bush), but it is more of a sensation than pain really. Anyway you will get to find out as you will be asked to show your child just how painless it is when you are being trained by injecting yourself! Don't do it if you are liable to cry, sob, weep for mercy, become hysterical or pass out... this sort of thing doesn't instil confidence you know!

As a last resort you can give the injection or transjection when they are asleep, most will sleep through it, incredible as it seems! But you should let them know what you've done, there is nothing like secrets and underhand doings to create mistrust and justify fear!

A nurse or a specialist from the company that makes that device will come to your home and train you how to use it. 24/7 on-call back up is offered. You will also probably be able to have all of the peripherals, hormone and so on delivered once every three months to your door by the drug company.

At the end of the day this has to become part of the fabric of everyday life, it can't be negotiable or an extraordinary event worthy of a sweets and presents. It has to be a routine like brushing teeth. The hospitals will do their utmost to make it easy for you.

Compliance is essential! This is a hugely expensive treatment regimen over many years and its effectiveness is reduced if you don't adhere to the programme. Slacking on the job will be frowned upon! It would be easy to let things slip, after all you child wont become sick, like a diabetic, if they don't have their jab but they won't grow as well and once the bones have matured you don't get a second chance.

Does it work?

Yes.

If your child commences the programme before they are 6 years old then it is believed they have an excellent chance of achieving their full genetic potential in height. If your child starts later then the results can still be very dramatic. NICE reported that increases in predicted height from 8.7cm to 10.7cm in boys and 7.7cm to 9.5cm in girls were recorded after 4.5 years to 8.1 years of treatment. Three to four inches is a significant uplift in height. As we've already said side effects are pretty few and far between.

Other effects are a change in your child's figure as growth hormone promotes a lean body mass. They will probably become slimmer and more muscular.

Growth normally shoots up and then tails off a little, though this could take a couple of years, until the centile line that is their intended line is reached. This line is then usually followed in the normal pattern to adulthood.

It is anticipated that successful treatment will see at least a 50% improvement on growth rate in the first year. If this doesn't happen the there would be a review.

Personal experience of this treatment with my own son has shown me that it is not an horrendous burden for the family and a dreadful ordeal for the child. It quickly becomes part of everyday life. Growth catch up is quick to set in and very pleasing... if expensive in clothes and shoes, particularly when you are used to clothes wearing out rather than being grown out of!

A Word About Grown-ups...

Sometimes growth hormone spontaneously starts to be produced, sometimes there is sufficient being produced for adult needs... but sometimes not. When there is still not enough GH then the treatment has to be continued throughout life. This won't mean that the person will continue to grow, but reduced GH can affect bone density and so increase the risk of osteoporosis earlier in life. It is also believed that GHD adults can suffer with depression and other illnesses.

One last thing...

If your child is short but has normal levels of GH, and GH therapy is not an option or would not improve stature as an adult, then you can be pleased that in this respect at least your child is healthy!



Glossary

HtSDS Height standard deviations - Essentially a standard deviation is the difference between a centile line and the one directly above or below it so the amount in terms of inches or centimetres varies with age... standard deviations are a maths persons 'correct' term!

If we go back to plotting the charts then most people have a Target Centile Range between the 9th and 91st centiles... that is the national average height range. So if your Mid-Parental Height is somewhere around the 50th centile (the average height) then if your child is below the 2nd centile they are more than 2 standard deviations below the average, i.e more than 3 centile lines below the average!

SD velocity standard deviation in growth velocity if a child's growth crosses a centile line in a 12 month period, usually going down 2 is cause for concern, such as dropping from the 25th centile to the 0.4 centile.

Bone age an x-ray of the left wrist is usually taken. The bones in the wrist grow in a fairly predictable time. Bones grow at their ends, called epiphyses, and then fuse (which is why adults, despite producing growth hormone, don't grow). The wrist x-ray shows how much time will occur until the bones fuse (and hence how much more remaining growth). This bone age can vary from the chronological age (actually how old the child is in number of years and months) by quite a bit.

Epiphyses the growth plates on the ends of bones. Bones don't grow from the middle. Once the epiphyses are fused then no more growth can happen and no amount of growth hormone can change that.

Endocrinologist specialist in the endocrine system... a gland doctor!