Growth Hormone Therapy in Children with Turner Syndrome, Noonan Syndrome, and SHOX Gene Mutations

This chapter will address several disorders characterized by varying degrees of growth failure. Turner syndrome (TS) is one of the most common human sex chromosome anomalies, occurring in about 1:2000 female live births. Girls with TS have an abnormal or missing X chromosome plus a phenotype that includes short stature, lymphedema, cardiac abnormalities, gonadal dysgenesis, and neurocognitive problems. Noonan syndrome (NS) is an autosomal dominant condition with a prevalence of 1 in 1000–2500 and a part of a group of disorders known as RASopathies. Noonan syndrome occurs in both boys and girls. In addition to varying degrees of short stature, features also include congenital heart defects, facial dysmorphisms, and mild intellectual disabilities. Defects in the short-stature homeobox-containing gene on the X chromosome (SHOX) lead to a variety of short-stare conditions: nonsyndromic short stature and Leri–Weill dyschondrosteosis (LWD), both due to SHOX haploinsufficiency. Homozygous loss of SHOX leads to Langer mesomelic dysplasia, a rare form of skeletal dysplasia.