Noonan syndrome affects one out of every 1,000 to 2,500 people, regardless of age, according to the Genetics Home Reference. The genetically based syndrome can cause short stature, heart defects, bleeding disorders and delayed puberty.
Teenage males with Noonan syndrome typically experience delayed puberty, including undescended testicles and a delayed or absent growth spurt. During adolescence, neck growth sometimes reveals a webbed neck or prominent trapezius muscles, according to Mayo Clinic. Adolescents typically have a wide forehead and a narrow chin. While most females with Noonan syndrome have a normal puberty and normal fertility, males often experience impaired fertility, possibly due to the undescended testicles.