Abstract
ObjectiveTo study the impact of the true mean daily dose and the true mean number of injections per week on the yearly height gain in short children treated with recombinant human growth hormone (rhGH).Design and Methods220 children from the French Easypod™ Connect Observational Study (ECOS) used the Easypod™ electronic device to record rhGH injections. The mean daily rhGH dose (the sum of the doses truly received divided by the number of days) and mean number of injections per week (the number of injections truly performed divided by the number of weeks) were calculated. Linear mixed models were used to study the impact of short (3-month) and long (1-year) variations in rhGH administration on the yearly height change [as a standard deviation score (SDS)], with time on treatment as a covariate. For each patient, several periods of 3 or 12 months were considered and designated as poorly adherence or fully adherence. We studied the impact of each of period on the height change.ResultsAt treatment initiation, the mean ± SD age was 9.8 ± 3.7 years (females: 47%, prepubertal: 86%) and the mean height was -2.28 ± 0.92 SDS. The mean treatment duration was 3.2 ± 1.1 years (685.2 patient years). 122 patients were GH-deficient, 79 were small for gestational age, and 19 had Turner syndrome. When treatment was computed over 12-month periods, receiving a mean daily dose <0.03 mg/kg.d was associated with a 20% lower mean yearly height gain SDS when<3 injections/week were received (vs.>5 injections/week), whereas maintaining a mean daily dose >0.03 mg/kg.d with<3 injections/week was not associated with a lower yearly height gain SDS (vs.>5 injections/week). For 3-month periods, changes in the daily rhGH dose or the number of injections per week over such short period did not influence the yearly height gain SDS.ConclusionThe 12-month treatment model showed that when poor adherence leads to a low true daily GH dose, the yearly height gain is low. The 3-month treatment model showed that poor adherence for short periods (<3 months) had no impact on the height SDS.
Highlights
Several height prediction models in patients treated with recombinant human growth hormone have been published over the last years [1,2,3,4,5,6]
Our present results highlighted the effect of variations in rhGH administration on the growth outcome in a relatively large French cohort of children using the connected EasypodTM device
Fair adherence (>5 injections/week) was observed for 64% of the periods in the first year, 61% in the second year, and 51% in the third year evidencing a decrease in adherence with treatment duration
Summary
Several height prediction models in patients treated with recombinant human growth hormone (rhGH) have been published over the last years [1,2,3,4,5,6]. Most of the models were designed to predict the height gain (expressed as a standard deviation score (SDS)) in various conditions with short stature, such as growth hormone deficiency (GHD), small for gestational age (SGA), and Turner syndrome (TS) [2, 7]. Most models considered the height gain over the first year, the second year, the third year, and later on, and sought to explain these endpoints with regard to several covariates. The application of these models revealed factors that influence the growth response to rhGH treatment and provided insight into how rhGH dose regimens could be personalized over the first years of treatment [8]. The impact of the rhGH dose is attenuated or null after the first few years [2, 7, 10,11,12,13,14]
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