The conclusion is based on a study published in the February issue of the journal Endocrinology. Using aging rats, researchers at the University of Illinois found that injected or implanted growth hormone stimulated the production of immunity-promoting hematopoietic cells in bone marrow, as well as in the spleen, liver and adrenal glands. Production in the treated elderly (2-year-old) rats was three times that of similarly aged, untreated rats and 80 percent of that in the more fit younger rats in the control group.
By 60 years of age, 30 percent of men have dramatically low concentrations of plasma insulin-like growth hormone-1 (IGF-I), falling to levels found in growth-hormone deficient children, said Keith W. Kelley, lead investigator and professor of animal sciences in the UI Laboratory of Immunophysiology. This is known as the somatopause of aging.
Some physicians now prescribe growth-hormone therapy to the elderly in an effort to counteract the effects of somatopause.
These new results show that growth hormone therapy of aged animals totally reverses the accumulation of fat cells in the bone marrow, Kelley said. This reduction in fat cells is accompanied by a huge increase in the number of both red and white blood cells in the bone marrow, which is dramatically reduced in the elderly. These results establish that a classic hormone, GH, is a potent stimulator of the production of blood cells.
Such a production process is called hematopoiesis. If similar results occur in the aged human, this kind of treatment approach could lead to an increase in the reserve capacity of both red and white cells, Kelley said.
Normal growth hormone production declines as people age. Muscle size and to
Contact: Jim Barlow
University of Illinois at Urbana-Champaign