Our son has Noonans and is now in his 30s. Growth hormone was discussed when he was very slow growing but we did not go for it then because it was harvested from cadavers. Now it is synthetic and would have considered that as an option if available at time. Like many Noonans kids he did not stop growing until about 21 and is now a "small" adult about 5ft 8inches. His son is getting growth hormone now but it is early days so we do not know how well it is working.Noonans was diagnosed in grandson and further testing has shown that son shares syndrome but not his sister who is of a similar height. Noonans was not a diagnosis when he was young. He has grown out of his "heart murmer",is fit, now eats well,has a degree and is doing OK.
http://www.noonansyndrome.org is excellent for information and access to growth charts for Noonans kids.