Effect of Growth Hormone Therapy in Patients with Noonan Syndrome: A Retrospective Study

BACKGROUND: Noonan syndrome is an autosomal dominant condition with an incidence of 1:1000 to 1:2500. The disorder is associated with distinct dysmorphic features, cardiac anomalies, developmental delay and delayed puberty. Short stature is a recognised feature of Noonan syndrome. OBJECTIVES: The aim of this study is to assess the effect of growth hormone treatment in patients with Noonan syndrome. METHODS: Retrospective data was collected from patients with Noonan syndrome treated with growth hormone. The results were analysed with variables expressed as mean values and standard deviation scores. RESULTS: Twelve Noonan syndrome patients (M: F = 10:2) treated with growth hormone were identified. The mean age of starting growth hormone was 8 years, with baseline height standard deviation score of -2.96 (range: -1.64 to -5.54). The height standard deviation score significantly improved to -2.50 (P = 0.0035) and then -2.22 (P = 0.0025), following one and two years of treatment, respectively. The average height velocity for the patients prior to starting treatment was 5.16cm/year (range: 2.4 - 8.2 cm/year), which significantly improved to 7.76cm/year (ranging from 4.1 to 12.8 cm/year) after one year of growth hormone treatment (P = 0.020) and to 6.51cm/year at the end of two years. CONCLUSIONS: Our study has shown that growth hormone treatment significantly improves the height standard deviation score of patients with Noonan syndrome over a two-year course of growth hormone therapy without any side effects. Further research is required to analyse the long-term effect of growth hormone therapy in patients with Noonan syndrome, including the impact on final adult height.