Growth Hormone Deficiency and the Chromosome 18 Conditions
We are often asked about the use of growth hormone to help children with the chromosome 18 conditions. It is easiest to address this question in reference to 18q deletions. We know that about 60% of children with distal 18q are GH deficient. There is already a peer-reviewed publication about the benefits of growth hormone (GH) in children with 18q-. That paper specifically showed that GH in GH deficient children with distal 18q deletions had neurocognitive benefits. (Peer-review publications means that the paper has been rigorously reviewed by peers and published in a medical journal. This is the “gold standard” for “evidence-based medicine”).
We do not have any peer-reviewed publications related to neurocognitive benefits of GH for children with any of the other chromosome 18 (Chr18) conditions. However, we have had numerous reports from families of observed benefit of GH for children with other Chromosome 18 conditions. Furthermore, there are an increasing number of publications related to neurocognitive benefits of GH in children with some other major chromosomal abnormalities.
That being said, I always suggest to parents that they ask their child’s pediatrician or specialist: “If my child did not have this genetic condition/s how would you evaluate my child for our concerns about my child’s growth”.
The great majority of children who are called “growth hormone deficient” (unrelated to Chr18 issues) are actually “growth hormone insufficient”. In other words, when the testing that is described below is done, the child produces some growth hormone, just not the amounts produced by typical children. (By way of analogy, if you have $100 in the bank, you are technically not “flat broke” but you are not going to plan a beach vacation next week.)
The testing is uncomplicated and takes about 3-4 hours. The test is typically called a growth hormone stimulation test or a growth hormone provocative test. This requires placing a blood drawing IV, obtaining a blood sample and then giving one or two medications that are known to cause a normal pituitary to release GH into the blood stream. A blood sample is obtained every 30 minutes for about 3 hours. The testing is routine, at least in the US, and generally considered safe. We average 3-4 of these tests every week here in Hershey. There are international standards as to what is considered a normal response and what is considered “deficient”.
GH itself has been around in clinical use since the 1960s. In its current form, it has been available since the late 1970s. It is basically safe and effective, primarily because it is biologically identical to what the normal human makes (i.e., like putting gas in the gas tank)! Generally, there are a few risks from GH treatment- and with the exception of an underactive thyroid (which is also easily treated) these risks have a prevalence of less than 1 in 1000 children. Most of the risks are actually related to conditions that are more common during periods of rapid growth (scoliosis, slipped capital femoral epiphyses).
We have no reason to believe that children with Chr18 problems are at any increased risk from GH treatment, but I do not think that there are 1000 children with Chr18 conditions on GH (at least not that I am aware of) so perhaps we have not yet treated enough children with Chr18 abnormalities.
Thus, my advice is to push to get the testing done if the child is not growing well. As a reminder, the various management guidelines suggest the prevalence of growth problems and GH deficiency in each of the conditions. Should you get “push back” from your pediatrician, one can gently bring up that we screen for a lot of conditions that are less common in children. For example, the newborn screen for hypothyroidism is done on all children when the prevalence is 1 in 3500 infants.
Then you have data and can review the options. As an aside, I do that with all children where there are concerns about growth.
Regarding the lack of expertise- the prevalence of the Chr18 conditions (other than trisomy) range from about 1:50,000 to 1:600,000. The general pediatrician has about 2000 children in his/her practice. The specialty pediatrician draws from a population of about 50,000 children. Thus, it is not surprising that the pediatrician or the specialty pediatrician does not know about Chr18 conditions – quite literally they have never seen a child with one of these conditions. I have been a practicing pediatric endocrinologist since 1980 and I first heard about Chr18 conditions, other than trisomy 18, when I moved to San Antonio in 1994. And even Trisomy 18, which is more common, merited about 3 sentences in a lecture somewhere along the way between 1974 and 1994.
