Long-term GH Treatment Improves Adult Height in Children with Noonan Syndrome with and Without Mutations in Protein Tyrosine Phosphatase, Non-receptor-type 11

Context: Noonan syndrome (NS) is characterized by short stature, typical facial dysmorphology and congenital heart defects. Short-term effect of GH therapy in NS is beneficial, reports on the effect on adult height are scarce.

Objective: To determine the effect of long-term GH therapy in children with NS.

Design: Twenty-nine children with NS were treated with GH until final height was reached.

Setting: Hospital endocrinology departments.

Patients: Children with the clinical diagnosis of NS, with mean age at the start of therapy of 11.0 years, 22 out of 27 tested children had a mutation in the protein tyrosine phosphatase, non-receptor-type 11 gene (PTPN11 gene). Interventions GH was administered subcutaneously at 0.05 mg/kg per day until growth velocity was 1 cm/6 months.

Main Outcome Measure: Linear growth (height) was measured at 3-month intervals in the first year and at 6-month intervals thereafter until final height.

Results: At the start of treatment, median height SDS (H-SDS) was -2.8 (-4.1 to -1.8) and 0.0 (-1.4 to +1.2), based on national and Noonan standards respectively. GH therapy lasted for 3.0-10.3 years (median, 6.4), producing mean gains in H-SDS of +1.3 (+0.2 to +2.7) and +1.3 (-0.6 to +2.4), based on national and Noonan standards respectively. In 22 children with a mutation in PTPN11 mean gain in H-SDS for National standards was +1.3, not different from the mean gain in the five children without a mutation in PTPN11+1.3 (P=0.98).

Conclusion: Long-term GH treatment in NS leads to attainment of adult height within the normal range in most patients.