Small body height

Question

Dear expert team,
My son has been diagnosed with CF at the age of 9 months. He has been breast-feeded until the age of 6 months. Until this point in time his body height lay exactly on the 50th percentile, his weight slightly higher on the 75th percentile. As the breast-feeding ended, he did not gain weigth anymore and also the height did not change anymore. For this reason a sweat test had been done which was positive.
In general, my son does relatively well. He did not have any relevant germs until now, therefore he did not have to take a course of antibiotics so far. The therapeutical measures include only physiotherapy so far (once a week) and of course pancreatic enzymes (creon 10 000).
In the meantime my son is 5 years and one month old. His height is for his age much to small with 103 cm (3rd percentile). Concerning his weight, he is one percentile higher (10th percentile).
My wife is with 155cm relatively small, I am of average height with 181cm. According to the height of the parents it cannot be expected that my son will be 190cm high, but we have of course the hope that he gains a quite average height (of probably 170cm).
Now to my question: We want to visit an endocrinologist, who should evaluate my son because of this. I know that CF has an influence of course on the thrift of a child, but how is it in the concrete case?
As the weigth of my son is over average compared to his height, I assume that he utilizes the food relatively well. According to this there arises the question in my opinion, if the small body height can only be related to the CF.
For us this is important, as we do not want to put him underneath the "torture" of daily injections of growth hormone (rhGH) if it does not help anything or only a bit.
What do you think about this? Is there a chance that rhGH can have some effect in my son?
Many thanks for your answer.

Answer

Hello,
you are worrying about the final height of your son, who was at the age of 6 month with the height in the region of the 50. age percentile and with the weight in the region of the 75 th age percentile. He has been diagnosed with CF at the age of 9 months. Now, with 5 years and 1 month, his height lies with 103 cm barely on the 3rd age percentile while his weight lies on the 10th age percentile. You wish, that your son will get at least a final height of about 170cm, as you as a father have a height of 181cm and the mother of 155cm.

First of all it has to be said that according to the good weight one can assume, that your son is fine-tuned quite well with the substitution of pancreatic enzymes. The measuring data for small children and especially babies are often not very exact, as the staff in a normal pediatric office often does not bother to measure exactly and as often suitable measuring instruments for this are lacking. Therefore the value of the percentile at the age of 6 months has to be regarded somehow critically.
In case one follows the actual height and the corresponding percentile until the adult age, your son will get a height of 165-170 cm with a certain safety. In order to get a greater certainty about this, your CF-physicians should do an x-ray of the left hand of your son, in order to determine the so-called prospective final height of your child. If this confirms the above mentioned target area, an endocrinological investigation is not necessary, as this targeted area corresponds to the genetically determined targeted area of the partnership and a treatment with growth hormone does not come into question.
We wish you and your family all the best
Yours sincerely,
Dr. H.-G. Posselt

09.12.2010