Noonan syndrome: growth to growth hormone - the experience of observational studies

Short stature is one of the key features of Noonan syndrome (NS). Attempts have therefore been made to improve height by means of recombinant human growth hormone (rhGH) treatment. Most of these endeavors were carried out either as case studies or observational studies. The overall experience in treating NS is still rather limited, and, in general, it can be said that the NS patients who received GH treatment represent a very narrow segment. The dosages applied in both the case studies and observational studies tended to be higher than those used in the replacement therapy of GH-deficient patients, but lower than in Turner syndrome patients. The NS studies have shown that the overall height gain of patients is small (5-10 cm), and that treatment usually begins at the age of about 10 years, at a height of approximately -3.0 SDS. This small response to treatment reflects the external treatment conditions (i.e. late age at GH start, low GH dose), but may also be associated with the fact that impaired sensitivity to GH is common in NS. Both case studies and observational studies are necessary in order to obtain further evidence about the efficacy and safety of GH treatment in NS.