Neurodegenerative diseases are a major focus of scientific and clinical interest because of their increasing medical and social importance. Due to the intimate connections between central nervous and endocrine systems, it is reasonable to suspect that important, and in some cases clinically relevant, endocrine modifications may accompany the progression of neurodegenerative diseases. Data on endocrine modifications in different neurodegenerative diseases have been reported, but results have often been non-conclusive, or conflicting. Accumulating evidence suggests that the GH/IGF-I axis is involved in the regulation of brain growth, development, and metabolism and in the regulation of muscle function. Dysfunctions in GH/IGF-I axis in most of neurodegenerative diseases are therefore reviewed. Alterations of this system could be actors in the complex network leading to (at least some) neurodegenerative diseases. A thorough effort in investigating every possible involvement is warranted, in the light of future therapeutic strategies.