Growth hormone/insulin-like growth factor I axis in neurodegenerative diseases

Neurodegenerative diseases (ND) are a group of heterogeneous disorders characterized by unknown etiology, subtle onset, and progressive involvement of neuronal systems leading to degeneration and dysfunction. They represent a challenge for basic science and clinical medicine because of increasing prevalence, social cost, complex biochemistry and pathology, and lack of mechanism-based treatments. Endocrine modifications may accompany the progression of ND, due to the intimate connections between central nervous and endocrine systems. Reported data on endocrine changes in different ND have often been non-conclusive or conflicting. GH/IGF-I axis is involved in the regulation of brain growth, development, and metabolism. Dysfunctions in GH/IGF-I axis in most of ND are therefore reviewed. Whether GH deficiency, when present, may act as a contributory factor in the pathogenesis of these diseases, or might represent a consequence of it is presently unknown. A thorough effort in investigating every possible involvement of GH/IGF-I axis is warranted, in the light of future possible therapeutic strategies.