FOR INFORMATION CONTACT:
Dr. George R. Merriam
(416) 595-1975 (6/18-20)
(416) 869-1600 (6/21-24)
Jeri Rowe
(206) 764-2435
Embargoed by the U.S. Department of Veterans Affairs
For Release on Friday, June 23, 2000 at 11:00 AM, EDT
ESTROGEN REPLACEMENT MAY NEGATE THE BENEFITS OF STIMULATING GROWTH HORMONE PRODUCTION IN ELDERLY
TORONTO - In a preliminary study, researchers have found evidence that boosting production of growth hormone can reduce body fat and help maintain levels of functioning in elderly men and women. However, these potential benefits may be undercut by estrogen replacement therapy. The findings were presented here today at ENDO 2000: The Endocrine Society's 82nd Annual Meeting.
"Our findings suggest that optimum hormone replacement in aging may require careful balancing among several systems," said George Merriam, M.D., Deputy Director of Research and Development for the VA Puget Sound Health Care System's American Lake Division and Professor of Medicine at the University of Washington.
Over all, the researchers found that boosting growth hormone (GH) production improved body composition and put people in a "holding pattern," Merriam said.
"We didn't see much functional improvement in the treated group, but saw declines in the group that received a placebo."
Levels of many hormones, including sex hormones and growth hormone, decline as people age, Merriam pointed out. Several current studies are focusing on whether replacing some or all of these hormones can promote healthier aging. In early trials, GH treatment showed promise, but was associated with side effects such as fluid retention and aching joints.
In an alternate approach, Merriam, Michael Vitiello, Ph.D., UW Professor of Psychiatry and Behavioral Sciences, Robert Schwartz, M.D., Director of Geriatric Medicine at the University of Colorado, and their colleagues are studying the use of GH-releasing hormone (GHRH) to increase the body's own production of GH in healthy men and women over age 65.
Normally produced by the brain's hypothalamus region, GHRH turns on the pituitary gland's production of GH. Growth hormone is best known for promoting growth in childhood but also has important functions in adults, such as regulating body fat, increasing muscle mass and capacity for aerobic exercise, and possibly supporting normal sleep and cognition.
It exerts many of its effects by stimulating release of insulin-like growth factor-I (IGF-I) in the liver and other tissues. Women generally produce more GH than men, but their IGF-I levels are not higher, and in older women the levels are actually lower than in men of similar age.
Many problems of aging resemble those seen in young people with growth hormone deficiency, Merriam pointed out, including reduced strength and energy and increased body fat. Studies of GH replacement in young people with pituitary disease have suggested that women are less sensitive than men to effects of GH treatment on IGF-I levels and body composition. Young women with pituitary disease (and who take an oral estrogen), need more GH to achieve a similar response.
"We wanted to take a closer look at the effect of gender and, in particular, how estrogen replacement alters our ability to stimulate growth hormone effects," Merriam said. Estrogen replacement therapy is becoming increasingly common to help ease menopausal symptoms and reduce risk for heart disease and osteoporosis in older women, he noted.
In their ongoing study, Merriam and colleagues so far have studied 21 men, 15 women not taking estrogen, and 11 women taking oral estrogen replacement, all over age 60. Volunteers gave themselves an injection each evening for 5 months. Half received synthetic GHRH injections and half a placebo (inactive substance). They were tested before and after treatment for hormone levels, body composition, physical performance, sleep and psychological function. Overnight measurements assessed changes in growth hormone levels.
Women, especially those taking estrogen replacement, had a greater GH response to GHRH than men, the researchers found. Despite the boost in GH secretion, however, women had a lower increase in the levels of IGF-I, and estrogen replacement nearly abolished this increase. GHRH treatment reduced body fat by about 5 percent, increased lean body mass and stabilized function.
The effects were greater in men than in women, and were blunted in the group taking estrogen. The effect of GHRH injections on GH production seemed to last only two to three hours and the researchers speculated that a longer-acting GHRH preparation might exert even stronger effects.
They caution, however, that their early results do not mean that GH stimulation should be recommended as routine treatment or preventive medicine. They are conducting a larger study to explore potential benefits, as well as possible risks of boosting growth hormone in the elderly.
The research is supported by the U.S. Department of Veterans Affairs, the National Institutes of Health, and the University of Washington General Clinical Research Center. Synthetic GHRH (serorelin acetate, Geref(r)) was donated by Serono Laboratories.
VA research provides improved medical care for veterans, as well as the general population. Through its unique affiliation with medical schools, VA plays a crucial role in educating future physicians in research and clinically oriented areas.
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SPECIAL NOTE FOR REPORTERS: Dr. George R. Merriam of the Puget Sound Health Care System will be available for press interviews. During the Endocrine Society's meeting, June 21-24, 2000, he can be reached at the Delta Chelsea Hotel, (June 18 thru 20) at (416) 595-1975 and the Westin Harbor Castle Hotel, (June 21 thru 24) at (416) 869-1600. Dr. Merriam can also be reached via the conference's Press Office (Room 803B) at (416) 585-3740. For additional assistance, please contact Jeri Rowe at (206) 764-2435 or Jim Blue at (212) 807-3429.
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