In this regard, mouse studies have shown that a lack of GH secretion resulted in a low level of IGF-I and that GH knock-out mice displayed osteopenia.32,33 Similarly, administration of IGF-I to GH deficient animals promoted skeletal growth.34 These data suggest that IGF-I plays an important role in mediating GH effects on the skeleton. This evidence concerns the gene GH1 and Osteopenia.