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G-16 Free Communication/Poster - Endocrinology MAY 31, 2008 7:30 AM - 11:00 AM ROOM: Hall B

The Effects of IGF-1 on Aerobic Muscle Endurance in Older Hyposomatotropic Men: Board #64 May 31 9:30 AM - 11:00 AM

Erceg, David N.1; Schroeder, E. Todd1; Kawakubo, Miwa1; Castaneda-Sceppa, Carmen2; Binder, Ellen F.3; Yarasheski, Kevin E.3; Bhasin, Shalender4; Sattler, Fred R.1; Azen, Stanley P.1

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Medicine & Science in Sports & Exercise: May 2008 - Volume 40 - Issue 5 - p S470
doi: 10.1249/01.mss.0000322994.34725.7f
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PURPOSE: We hypothesized that augmenting IGF-1 levels resulting with rhGH administration will be associated with improved aerobic muscle endurance measures at age related or youthful T levels.

METHODS: We conducted a 16-week, double blind, placebo controlled, factorial trial in older healthy, hyposomatotropic, community dwelling men. Participants were randomized to receive rhGH at 0, 3.0 or 5.0 μg/kg/day in combination with transdermal T at 5 or 10g / day. Muscular endurance (ME) was determined by two cycle ergometer tests: 1) VO2peak using a ramping protocol to volitional fatigue, and after a 30 min rest period 2) an aerobic endurance (AE) by measuring time to failure at 80% of the max workload (watts) reached during the VO2peak test. The 4 groups receiving rhGH were combined for statistical analyses. t-tests were used to assess within and between group changes, while correlation analyses were used to assess the relationship between IGF-1 and ME measures.

RESULTS: Subjects were 70.8±4.6 years of age with pretreatment IGF-1 levels below the adult lower tertile <167ηg/dL and BMI=27.8±3.3kg/m2. The rhGH group showed significant increase in IGF-1. Both groups significantly improved AE, but not VO2peak. No significant correlations were determined between IGF-1 and ME measures: IGF-1 and VO2peak, R = 0.16 (p = 0.41) and 0.15 (p = 0.25) for placebo and GH treatment groups, respectively. For IGF-1 and AE, R=−0.01 (p = 0.98) for placebo and 0.19 (p= 0.15) for GH treatment groups.

CONCLUSIONS: The data suggest that augmenting levels of IGF-1 in older hyposomatotropic men may not result in improvements in ME measures. However, there may be an effect or interaction with T status since AE increased significantly in subjects whether or not they received rhGH.

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©2008The American College of Sports Medicine