Growth and Growth Hormone Treatment in Noonan Syndrome.

Short stature is a common characteristic of Noonan Syndrome (NS), a genetic condition caused by mutations affecting the RAS / mitogen-activated protein kinase (MAPK) cascade. Growth hormone (GH) has been used to normalize childhood growth and increase adult height in NS. GH is effective in increasing growth velocity, and significantly improves height SDS at adult height. Studies of GH treatment to adult height have shown height gains of 9.5-13.0 cm for males and 9.0 - 9.8 cm for females. Factors associated with improved height outcomes are earlier initiation of therapy, a greater height SDS at pubertal onset, and a longer duration of GH therapy. The safety data to date is reassuring and includes no evidence of adverse cardiac effects or increased occurrence of malignancies. Further studies will likely clarify the role of different RAS/MAPK pathway aberrations in growth and GH responsiveness. Continued surveillance is needed to assure the long term safety of GH therapy.