medwireNews: Factors including age at initiation of growth hormone (GH) therapy and severity of inflammation during treatment determine whether children with juvenile idiopathic arthritis (JIA) will achieve a favourable growth outcome, study results show.

The researchers stress that “clinical monitoring of growth remains crucial”, because the “loss of height observed during JIA, unpredictable severity of the disease, and limiting effects of chronic inflammation on the growth response to GH support the initiation of GH therapy before the growth deficiency becomes severe.” GH is not currently licensed for use in JIA patients in Europe, however.

Dominique Simon (Hôpital Robert Debré, Paris, France) and co-workers assessed data from 48 patients participating in three studies, which used average GH doses of 0.065 to 0.085 mg/kg per day.

“There is no consensus so far about the optimal GH dosages for patients with JIA, and no study has compared long-term growth outcomes with different GH dosages”, the team observes in The Journal of Clinical Endocrinology & Metabolism.

The children were diagnosed with JIA at a median age of 3.7 years, were started on glucocorticoid therapy at 4.0 years and on GH treatment 5 years later, when they were a median of 10.1 years old. By this time, their growth velocity was much reduced and they had a median height standard deviation score (SDS) of –2.8.

The patients continued GH therapy for a median of 6.5 years, with 60% continuing it until they had attained their final adult height, which was within the normal range for 52% of patients. The 46 patients whose target height was known achieved a height that was a median of 9 cm below target or –1.3 SDS.

After accounting for confounders, older age at GH initiation and more severe inflammation during follow-up (reflected in C-reactive protein levels) were associated with a significantly reduced likelihood of a favourable growth outcome, defined as an adult height SDS of –1.5 or better.

The researchers also found evidence, albeit not significant in the multivariate analysis, of a detrimental effect of higher glucocorticoid dose and duration of treatment on growth outcomes, which they say is “consistent with the effect of inflammation on growth.”

In addition, they note that patients treated with biological therapy tended to do better than untreated patients, with 63.3% versus 31.3% achieving a favourable growth outcome.

“Thus, the growth improvement observed in our patients was likely due to combined effects of GH treatment and steroid-sparing biologics”, the team suggests.

By Eleanor McDermid

J Clin Endocrinol Metab 2017; Advance online publication

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