Growth hormone therapy for kids -
An early start to growth hormone therapy
For children with idiopathic short stature (ISS), growth hormone therapy is usually started at the age of 3-4 years, although early initiation of therapy is recommended, parents usually don’t notice that their children are short until they are at school age, when there is comparison with other children.
In any case, growth hormone therapy should be started in pre-pubertal age (girls not more than 6 years of age, boys not more than 7 years) to optimize growth outcomes. [Int J Pediatr Endocrinol 2013;2013:22]
In addition to younger age at start of growth hormone therapy, other variables associated with better response in patients with ISS include first-year growth response, the difference in height at the start of treatment from target height SDS, and growth hormone dose.
Further, height at onset of puberty highly influences final height. Pre-pubertal children with ISS who show an appropriate first-year response to GH are likely to benefit from long-term treatment, even on a low dose of growth hormone. [Horm Res 2007;68:53-62]
First year growth velocity: An important predictor
The first year of growth hormone treatment is very important because growth during this period is often fastest and can affect how much the patient is likely to grow later. If the child does not respond to growth hormone therapy in the first year of treatment, it is expected that the treatment will not be successful later on.
Further, if a very high dose is required to achieve a positive response in the first year of treatment, it can be inferred that the patient is GH-resistant to a certain degree.
Kriström and colleagues recently developed a model using growth response data from 162 pre-pubertal children born at term. The model was constructed to predict long-term growth response to growth hormone therapy based on observed first-year growth response.
It serves as a tool for identifying those children who may benefit from long-term growth hormone treatment. This model is valid worldwide for the prediction of up to 7 years of pre-pubertal growth in children with ISS. Figure 1 shows the observed growth response, for comparison with the predicted growth response made after 1 year on treatment, on the four variables: age, gender, height at start of treatment and height after 1 year on GH treatment. [BMC Med Inform Decis Mak 2009;9:1]
Figure 1. GH response chart for visualization of Response Scores on different levels Reference source: BMC Med Inform Decis Mak 2009;9:1
Left panel: The response score (RS) gives a measure of growth in response to GH. For each individual child at treatment time 1 year (x-axis), the observed growth response (Δheight SDS) is found on the y-axis to the left and following the corresponding curve the individual RS can be found to the right.
Middle panel: Observed first-year Δheight SDS on treatment for three prepubertal children from the validation group (filled circles). The individual calculated RS (dotted line) is found on the right axis.
Right panel: Individual RS from the same three children, based on observed Δheight SDS on treatment at different time points (filled circles at treatment time 2, 3, 4, 5 and 6 years) in comparison with the predicted (dotted line). RS was consistent over time within an individual child, and the inclusion in the model of measurements made later than 1 year after the start of growth hormone treatment are acceptable.
Growth velocity in pre-pubertal children is normally 4-6 cm/year. A growth velocity of 8 cm/year during the first year of therapy is considered a good response in pre-pubertal children.
In the second and third year of therapy, the rate may decrease to 7 cm/year, however, for children with a baseline growth velocity of < 4 cm/year, a growth velocity of 6 cm/year in the first year of treatment is still considered a good response.
The observations are consistent with results of a recent study showing rapid growth (up to 8-12 cm) in the first year of growth hormone therapy. Thereafter, growth velocity slows to a rate more closely matching natural growth.
The information provided on this website are for educational purposes only. Please consult your physicians before considering treatment or for detailed medical advice.