Long-term GH increases height, not growth potential in juvenile arthritis

Researchers in France reported that although long-term treatment with growth hormone improved growth in patients with juvenile idiopathic arthritis, therapy did not fully restore patients’ genetic growth potential.

“Recombinant human growth hormone therapy has been investigated as an intervention to improve growth and decrease adverse metabolic outcomes in patients with severe chronic diseases,” Dominique Simon, MD, PhD, of the Assistance Publique-Hopitaux de Paris, and colleagues wrote.

The researchers noted that previous studies found GH aided growth velocity, muscle mass and bone mineralization in patients with juvenile idiopathic arthritis.

“Adult height has been evaluated in a single controlled study, which showed a significant improvement after 6 years of growth hormone therapy, with a mean height gain of 1.57 [standard deviations] and considerable variability in the growth response according to disease severity,” Simon and colleagues wrote. “Although this study was controlled, its small sample size of 13 patients limits its validity.”

The researchers analyzed data on 58 patients with juvenile idiopathic arthritis who were enrolled in three prospective clinical trials between 1997 and 2002. Fifty-three patients received GH treatment. The main outcomes were factors associated with favorable growth outcome.

Those who underwent treatment with GH (n = 53) received therapy for a median of 6.5 years. Among the 48 patients whose adult height was available 8.6 years after initiating therapy, standard deviation scores for height rose from -2.9 at baseline to -1.7 in adulthood, the researchers reported (P < .001); however, the patients’ median height in adulthood was still below target height (-0.2 standard deviation score; P < .001), with a corrected adult height at -1.3 standard deviation score.

Twenty-four patients (52.2%) had favorable growth outcomes, the researchers wrote. Age at initiation of GH therapy (adjusted OR = 0.68 per additional year; 95% CI, 0.47-0.99), height at GH initiation (adjusted OR = 2.6 per additional standard deviation score; 95% CI, 1.15-5.9) and mean C-reactive protein levels in follow-up (adjusted OR = 0.51 per additional 10 mg/L; 95% CI, 0.28-0.92) were all significant independent determinants of growth outcome, according to Simon and colleagues.

They noted that response to GH varied significantly in individual patients and that disease severity was the main limiting factor.

“Biologic agents are currently more efficient in achieving tight inflammation control and thus ensuring optimal growth in patients with [juvenile idiopathic arthritis],” the researchers wrote. “However, clinical monitoring of growth remains crucial to detect persistent growth failure leading to significant short stature in poor responders, who may benefit from GH therapy.” – by Andy Polhamus

Disclosures: Simon reports honoraria from Pfizer as a clinical investigator in studies that provided data for the current study. No other authors report any relevant financial disclosures.