Besides the mutations that may occur in the GHR, JAK2, or STAT5β genes and result in a severe primary IGF-1 deficiency and short stature [81,82,83], there are some malfunctions of the GHR-JAK2-STAT pathway which may be caused by many modulators, some of which may be linked to eating habits or result from the action of other modifiable factors, one of them being SIRT1 [5]. This evidence concerns the gene JAK2 and growth delay due to insulin-like growth factor type 1 deficiency.