BRISTOL, UNITED KINGDOM. Several studies have shown powerful associations between blood levels of insulin-like growth factor-I (IGF-1) and the risk of colon cancer, prostate cancer, and premenopausal breast cancer. As a matter of fact, recent evidence indicates that high IGF-1 levels may be more important than other previously reported risk factors for cancer. IGF-1 is released by human growth hormone and stimulates growth throughout fetal and child development. IGF-1 in the body is normally tightly bound to a large protein molecule (IGF binding protein-3) and there is evidence that high levels of IGF binding protein-3 protect against the development of certain cancers.
A distinguished group of medical researchers at the University of Bristol now voice concern about the increasing use of IGF-1 and growth hormone enhancers by body builders and elderly people trying to recapture their vanishing youth. They suggest that IGF-1 may increase both cell turnover and the susceptibility of cells to become cancerous. They also point to recent evidence that indicates that IGF-1 prevents the programmed death (apoptosis) of cancer cells. The researchers warn that people using growth hormone and IGF-1 enhancers are unlikely to be aware of their potentially harmful effects.
The pharmaceutical industry is well aware of the increasingly clear association between IGF-1 and cancer. Chemotherapeutic drugs are being developed to block the activity of IGF-1 or enhance the activity of IGF binding protein-3.
Smith, George Davey, et al. Cancer and insulin-like growth factor-I. British Medical Journal, Vol. 321, October 7, 2000, pp. 847-48 (editorial)