Researchers from Wake Forest University School of Medicine and other centers have demonstrated that a modest suppression of growth hormone and related compounds beginning in early adulthood may delay the onset or progression of several types of cancer.

Suppression of growth hormone and insulin-like growth factor ( IGF-1 ) also may decrease cancer risk in those individuals at high risk for disease, and perhaps could be a preventive measure, said William E. Sonntag, the lead investigator, who based his findings on research in rats.

IGF-1 is an important blood-borne factor that increases cell growth and prevents cell death and has been proposed to be a factor in the initiation of cancer.

" Elevated IGF-1 levels in pre-menopausal women have been demonstrated to be a risk factor for breast cancer as well as numerous other cancers," said Sonntag, at the School of Medicine, a part of Wake Forest University Baptist Medical Center.

IGF-1 in the blood also may act as a tumor promoter during the early development of cancer.
Although additional research is needed, he said, drugs in the Somatostatin class are currently available to suppress growth hormone and IGF-1 in people, so Somatostatin analogs could be given as preventative measures to lower plasma IGF-1 before the onset of disease, especially in high-risk people.

In a previous study, rats with high levels of growth hormone, a circulating factor that increases IGF-1 levels, exhibit an increase in spontaneous mammary tumors. Dwarf animals with 50 percent lower IGF-1 levels do not develop tumors in response to a chemical carcinogen. But Sonntag said that if these dwarf rats are given growth hormone to increase IGF-1 in the blood, tumors develop at the same rate as in the normal animals.

Suppression of IGF-1 activity inhibits the proliferation of numerous cell types and cancers. " IGF-1 levels in the blood can be reduced by low-calorie diets, which could be a mechanism for the diet-cancer relationship, " said Sonntag.

Previous studies in some animals indicate that a reduction in IGF-1 activity increases lifespan. To date, there are no studies of a specific suppression of IGF-1 on aging or age-related diseases.

In the current study, Sonntag found that a life-long deficiency of IGF-1 decreased cancer risk by approximately 45 percent and decreased cancer deaths by 12-15 percent.

" Besides reducing the incidence of cancer in these rats, we found that a modest suppression of plasma IGF-1 beginning shortly after puberty and continued throughout life reduces the incidence of kidney disease and increases lifespan," Sonntag said.

Source: ENDO 2005, the Annual Meeting of the Endocrine Society

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