LAUSR

Abstract Context: There is no consensus on the effect of recombinant human growth hormone (rhGH) therapy on skeletal maturation in children despite the current practice of annual monitoring of skeletal maturation with bone age in children on rhGH therapy. Aims: To investigate the effects of long-term rhGH therapy on skeletal age in children and explore the accuracy of bone age predicted adult height (BAPAH) at different ages based on 13 years of longitudinal data. Methods: A retrospective longitudinal study of 71 subjects aged 2-18 years, mean 9.9 ± 3.8y, treated with rhGH for non-syndromic short stature for a duration of 2-14y, mean, 5.5 ± 2.6y. Subjects with syndromic short stature and systemic illnesses such as renal failure were excluded. Results: Bone age minus chronological age (BA-CA) did not differ significantly between baseline and the end of rhGH therapy (-1.05 ± 1.42 vs -0.69 ± 1.63, p=0.09). Piece-wise regression however showed a quantifiable catch-up phenomenon in BA of 1.6 months per year of rhGH therapy in the first 6.5y, 95%CI 0.023 - 0.229, p=0.017, that plateaued thereafter, β=0.015, 95% CI -0.191-0.221, p=0.88. There was no relationship between BAPAH z score – height z score and the duration of rhGH therapy, p=0.68. BAPAH overestimated final adult height in younger subjects but became more precise in older subjects (p<0.0001). Conclusion: Long-term rhGH therapy demonstrated an initial catch-up phenomenon in skeletal maturation in the first 6.5y that plateaued thereafter with no overall significant advancement in bone age. These findings are reassuring and do not support the practice of yearly monitoring of skeletal maturation with bone age in children on rhGH therapy, especially in younger subjects where BAPAH is imprecise.