ESPE Abstracts

Background: In patients with HC due to N540K FGFR3 mutations, adult height ranges 138–155 cm (men) and 128–145 cm in women. We have previously reported that a mean 0.075 μg/k.d rGH dose could allow a gain of 1.9 S.D. of height over 6.1 year and could reduce body disproportion in 6 young patients (Journal of Pediatrics 2012).

Objectives: To confirm these results and extend observation of rGH effects.

Patients: Starting at 1.8–7 year of age, 10 HC patients received cumulative 0.081±0.009 mg/k.d rGH with repeated planned breaks from treatment and frequent measurements of height, body proportions, and serum IGF1. At 10 years of age in 2 girls and 11 in 2 boys, GnRH analogs were used to delay puberty and epiphyseal closure.

Results: Current duration of treatment ranges 1–10 years. Mean IGF1 values averaged 2.3±0.3 S.D. during rGH treatment. As previously observed, patients treated before 3 yrs gained height actively and stabilized near the −2S.D. height line. Patients treated at an older age showed a more reduced catch-up effect. Despite efficient blockade of puberty, femoral and tibial growth plates underwent a rapid with almost complete closure around 13 years of age; thereafter height started to plateau despite continuing rGH treatment.

Conclusion: rGH treatment in patients with HC i) show clearcut positive results when started early ii) are more limited if started in mid-childhood iii) cannot maintain growth acceleration at adolescence iv) seems to end its effect around age 13. The current observations are preliminary and should be confirmed in larger studies of this rare chondrodysplasia. However, this report can serve as a warning for an early treatment and for trying to maximize rGH effects in infancy and early childhood.