IGF1 and cancer: The underlying mechanisms are still mostly unknown for different sites of cancer; however, some potentially PA-modulated parameters, such as insulin sensitivity (e.g., insulin levels, C-peptide, and insulin like growth factor 1), the immune system (e.g., natural killer cell cytotoxic activity, total lytic units, and spontaneous lymphocyte proliferation), and inflammation [e.g., C-reactive protein (CRP) and serum amyloid A] appear to be involved in tumor development [16–18].