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Older men with low testosterone levels have increased bone density at the hip after four months of growth hormone and testosterone replacement therapy, according to a new study. The results will be presented Monday at The Endocrine Society’s 92nd Annual Meeting in San Diego.

Researchers know that growth hormone stimulates bone formation and that testosterone replacement therapy increases bone mineral density, as shown on DEXA (X-ray) bone scans.

What is notable about the new study, said its lead author, Lindsey Anderson, MS, of the University of Southern California, Los Angeles, is that when combined with growth hormone therapy, “a relatively short duration of testosterone and growth hormone shows changes in hip bone strength. So you don’t have to load up these older men with a lot of testosterone and growth hormone to see benefits.”

As people age, their bone mass decreases and osteoporosis can develop. Osteoporosis affects 2 million U.S. men, and another 12 million men are at risk of the bone-weakening disease, which increases the chance of suffering a disabling fracture of the hip, spine or wrist.

Anderson and her colleagues randomly assigned 112 men, ages 65 to 90 years, to one of six treatment groups. All men received a testosterone skin gel, with three groups receiving a low dose of 5 grams and three groups receiving a   higher dose of 10 grams daily. For each testosterone dose, one group received no growth hormone therapy and two groups received injectable growth hormone at either a low dose—3 micrograms per kilogram of body weight per day (μg/kg/day)—or high dose (5 μg/kg/day).

The researchers detected the effects of growth hormone by measuring blood levels of insulin-like growth factor 1 (IGF-1), a hormone that has tissue-building effects in adults. For evaluation of bone density of the hip, study subjects had a DEXA scan before and after 16 weeks’ treatment.

Of the 112 men, 76 completed DEXA scans at both time points. At least one measure of hip bone strength—higher bone density at one or more areas of the hip—increased for the two groups receiving high-dose growth hormone with testosterone as well as for the group receiving low-dose growth hormone plus high-dose testosterone.

Statistical analyses showed a relationship between increased IGF-1 levels in the blood and increased bone strength of the trochanters, the bony points of the hip. There was no relationship between testosterone alone and hip bone strength, the authors reported.

Because no group received growth hormone alone, the researchers cannot attribute the improved hip bone strength to either drug alone, Anderson stated. Rather, she said, “the improvement could be the result of a combination of the drugs. Testosterone and IGF-1 appear to be important hormones for maintaining bone mass in older men.”

Grant support for the study came from the National Institutes of Health and the U.S. Department of Agriculture’s Agricultural Research Service. Solvay Pharmaceuticals, Genentech and TAP Pharmaceuticals (now part of Takeda) supplied the study drugs.
 

 

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Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Md. To learn more about the Society, and the field of endocrinology, visit our web site at www.endo-society.org.