Sunday, March 14, 2010

Does growth hormone promote cancer? By Jerry Brainum

Human growth hormone (GH) is popular among both athletes and those seeking anti aging therapy. From an athletic standpoint, GH is thought to provide anabolic effects, and also to be synergistic when used with other hormones, such as anabolic steroids and insulin. There is little or no evidence, however, that using GH alone will provide any significant anabolic effects, unless the person using it is deficient in GH. Most of the anabolic effects associated with GH don't come from GH, but instead come about because GH promotes the synthesis and release of another hormone, Insulin-like growth factor-1 (IGF-1). On the other hand, the IGF-1 release promoted by GH occurs in the liver, and the IGF-1then circulates in the blood, mostly bound to certain proteins. Recent studies show that systemic IGF1 isn't required to make muscular gains. What's more important in this regard is the local production of IGF-1 in muscle. This local muscle release of IGF-1 plays an important role in muscle repair and growth after exercise.

From an anti-aging viewpoint, GH is thought to exert beneficial effects though maintaining various tissues and organs of the body that would otherwise slowly degenerate with the passing years. Indeed, levels of GH peak during the teen years, then begin to decline starting at age 40. Many older people are clinically deficient in GH, and much of the ills associated with aging are often linked to GH deficiency. As noted, however, the active anabolic effector of GH is IGF-1. When people who are deficient in GH undergo GH therapy, IGF-1 always rises significantly. This rise in IGF-1, however, could present problems. Among the many functions of IGF-1 are a stimulation of cellular division and a preservation of cells through inhibiting a type of cellular suicide called apoptosis. The basis of cancer is uncontrolled cell division, and some studies link higher levels of IGF-1 with a greater incidence of certain cancers, such as cancers of the breast, colon, and prostate. While the mechanism makes sense, the relationship of IGF-1 to cancer is still not clear. For one, most active IGF-1 is bound to proteins, and cannot exert effects on the cell until it is freed from its binding protein. Another factor is that most older people, in whom cancer rates tend to be higher, also have low levels of both GH and IGF-1. A recent study followed 633 older men for 18 years, and found that the men with the highest levels of IGF-1 also showed the highest rates of cancer deaths. Other studies, however, have not shown any such association. One difference in the new study was that the study subjects were older than in previous studies. In the new study, the subjects average age was 74. Based on this finding, the authors of the study suggest that IGF-1 may play a role in cancer in older men. In younger men, IGF-1 is known to protect both heart and brain tissues. The authors also suggest that in light of the association between elevated IGF-1 levels and cancer in older men, perhaps GH therapy may be not as beneficial as some people believe. What they didn't mention was that long-term studies of GH therapy in older men show no elevated rates of cancer in the men. This can be attributed to the fact that even though IGF-1 levels increase with GH therapy, so does the IGF-1 binding protein, thus protecting cells from any adverse effects of a rise in IGF-1, although the beneficial effects on mind and body likely remain.
Major JM, et al. Insulin-like growth factor-1 and cancer mortality in older men.J Clin Endocrin Metab2010;95:1054-1059.

©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.

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