Effect of growth hormone on aging connective tissue in muscle and tendon: gene expression, morphology, and function following immobilization and rehabilitation.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 24235105 · doi:10.1152/japplphysiol.01077.2013
What was done
Twelve elderly men (aged 65–75 years) underwent 2 weeks of single-leg immobilization followed by 6 weeks of retraining. Participants were randomized to receive daily injections of recombinant growth hormone (rhGH; n = 6) or placebo (Plc; n = 6). Quadriceps and patellar tendon cross-sectional area (CSA), maximal voluntary contraction (MVC), and tendon biomechanics were measured. Muscle and tendon biopsies were analyzed for collagen (COL1A1/3A1) and IGF-1 (IGF-1Ea/Ec) mRNA expression, alongside transmission electron microscopy for fibril morphology.
What was found
The abstract does not report exact numerical values or effect estimates. Tendon CSA and biomechanical properties did not change during immobilization, but tendon CSA increased after 6 weeks of rehabilitation in both groups, with larger increases in the GH group. Patellar tendon stiffness increased in the GH group. Muscle CSA decreased post-immobilization in the placebo group but was preserved in the GH group; subsequent muscle CSA gains during retraining were significantly larger with GH. Muscle mRNA expression of IGF-1Ea/Ec and COL1A1/3A1 increased after immobilization and retraining with GH, whereas the placebo group only showed increased IGF-1Ec expression after retraining.
Why it matters
This study suggests growth hormone may protect musculotendinous tissue during disuse and accelerate structural remodeling during subsequent rehabilitation in older adults by promoting collagen and IGF-1 expression.
Limits
The study is severely limited by a very small sample size (n = 6 per arm) and included only healthy elderly males. The abstract does not provide exact numerical data, confidence intervals, p-values, or clinical/functional strength (MVC) results.
Cited by
- supports Growth hormone strengthens tendons.