Does Growth Hormone Cause Cancer?

P. J. Jenkins; A. Mukherjee; S. M. Shalet


Clin Endocrinol. 2006;64(2):115-121. 

In This Article

The GH/IGF-1 Axis

In addition to its classical endocrine actions, the GH/IGF-1 axis is increasingly recognized to have important effects at a paracrine and autocrine level.[1] Factors influencing the tissue-specific effects of IGF-1 include not only the density of the type 1 IGF-1 receptor, but also the presence of IGF-1/insulin receptor hybrids and the effects of the various IGF-binding proteins. In addition to regulating the amount of free IGF-1 available, a number of the binding proteins have IGF-1-independent actions of their own which may oppose the effects of IGF-1 itself. Complexity is further added to the system by the presence of various proteases that cleave the ligand from its binding protein. These include prostate-specific antigen (PSA), a protease for IGFBP-3, although it is uncertain whether its increased levels in the serum of patients with prostate carcinoma are causal or as a result of the cancer itself. Finally, local IGF-1 bioactivity is also influenced by tissue architecture and variations in proteoglycans, perhaps as a result of their varying affinities for the different binding proteins.