Testosterone administration to elderly men increases skeletal
muscle strength and protein synthesis.
Urban, Randall J., Yvonne H. Bodenburg, Charles Gilkison, Judy
Foxworth, Andrew R. Coggan, Robert R. Wolfe, Arny Ferrando.
Department of Internal Medicine, Department of Physical Medicine
and Rehabilitation, Department of Anesthesiology, Department of
Surgery, University of Texas Medical Branch, Galveston, TX 77555
-1060, Shriners Burns Institute, Galveston, TX 77550
APStracts 2:0124E, 1995.
Aging men develop a significant loss of muscle strength that occurs in
conjunction with a decline in serum testosterone concentrations. We
investigated the effects of testosterone administration to 6 healthy
men (mean SEM, 67 2 years) on skeletal muscle protein synthesis,
strength, and the intramuscular insulin-like growth factor-I (IGF-I)
system. Elderly men with serum testosterone concentrations of 480
ng/dL or less were given testosterone injections for 4 weeks to
produce serum concentrations equal to those of younger men. During
testosterone administration muscle strength (isokinetic dynamometer)
increased in both right and left hamstring and quadricep muscles as
did the fractional synthetic rate of muscle protein (stable isotope
infusion). RNase protection assays done on total RNA from muscle
showed that testosterone administration increased mRNA concentrations
of IGF-I and decreased mRNA concentrations of insulin-like growth
factor binding protein-4. We conclude that increasing testosterone
concentrations in elderly men increases skeletal muscle protein
synthesis and strength. This increase may be mediated by stimulation
of the intramuscular IGF-I system.
Received 13 April 1995; accepted in final form 25 May 1995.
APS Manuscript Number E175-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 June 1995.