Activation of the MAPK pathway (RASopathies) and partial growth hormone insensitivity.

RASopathies are a heterogeneous group of syndromes caused by germline mutations in genes encoding components of the RAS/MAPK pathway. Postnatal short stature is a cardinal feature of the RASopathies. Although the pathophysiology of these conditions is not fully understood to date, growth hormone insensitivity is one possibility, based on the observation of low IGF-1 values, generally preserved GH secretion and suboptimal growth response to recombinant human GH therapy. In this review, we will discuss the clinical and experimental evidence of GH insensitivity in patients with Noonan syndrome and other RASopathies, as well as their molecular basis.