NEW YORK (Reuters Health) - Ten years of growth hormone treatment improves muscle strength in adults who have a deficiency of the hormone. The first five years of treatment restores muscle strength, and the second five years and thereafter slow age-related loss of strength, Swedish investigators say.

Adults with growth hormone deficiency tend to have excess body fat and reduced muscle strength, but little is known about the effect of prolonged growth hormone therapy on muscle strength.

Dr. Galina Gotherstrom and colleagues at Goteborg University evaluated the effects of 10 years of treatment on muscle strength and neuromuscular function in 109 subjects, average age 50 years, with adult-onset growth hormone deficiency.

"Growth hormone replacement induced a sustained increase in lean mass and isometric knee flexor strength" during the first five years, the researchers report in the Journal of Clinical Endocrinology and Metabolism. In addition, there were increases in upper leg and handgrip strength during the first five years of the study.

Over the next five years, muscle strength decreased, returning to initial levels or even lower. However, once age and gender were taken into consideration, "there were sustained and... even progressive increases in the measures of muscle strength" through seven years of follow-up, Gotherstrom and colleagues found.

The net results was that, after 10 years of growth hormone replacement, leg and hand strength was virtually normalized, the team concludes.

SOURCE: Journal of Clinical Endocrinology and Metabolism, March 2009.

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