The effect of recombinant equine growth hormone on the biomechanical properties of healing superficial digital flexor tendons in horses.
Authors: Dowling Bradley A, Dart Andrew J, Hodgson David R, Rose Reuben J, Walsh William R
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Superficial digital flexor tendon (SDFT) injuries remain a significant concern in equine practice, yet therapeutic interventions to optimise healing remain limited. Dowling *et al.* investigated whether recombinant equine growth hormone (rEGH)—a treatment proposed to enhance tissue repair—could improve biomechanical properties during SDFT healing, using a collagenase-induced tendonitis model in 12 Standardbred horses over a six-week treatment period commencing one week post-injury. Rather than demonstrating benefit, rEGH-treated tendons exhibited significantly larger cross-sectional areas but substantially reduced ultimate and yield tensile stress alongside decreased stiffness compared to saline controls, indicating structurally weaker tissue despite increased volume. These findings suggest that growth hormone administration during early tendon healing may promote cellular proliferation without adequate collagen organisation or maturation, resulting in biomechanically inferior repair that could increase re-injury risk. Whilst this 2002 work is now two decades old, the cautionary outcome warrants consideration in contemporary regenerative medicine discussions; clinicians should exercise restraint recommending rEGH for acute SDFT pathology until evidence demonstrates improved functional outcomes or long-term follow-up data clarifies whether these early-phase biomechanical deficits persist or resolve during later remodelling phases.
Read the full abstract on PubMed
Practical Takeaways
- •Do not use recombinant equine growth hormone to treat superficial flexor tendonitis in the acute/early healing phase, as it weakens rather than strengthens healing tendons
- •rEGH increases tendon cross-sectional area but produces mechanically inferior tissue with reduced load-bearing capacity during early healing
- •Focus rehabilitation protocols on established evidence-based therapies rather than growth hormone supplementation for acute SDFT injuries
Key Findings
- •rEGH-treated tendons developed significantly larger cross-sectional areas compared to control tendons
- •rEGH treatment resulted in lower ultimate and yield tensile stress values, indicating weaker mechanical properties
- •Control tendons were biomechanically stiffer than rEGH-treated tendons
- •rEGH administration in early healing phase (week 1-7 post-injury) produced negative effects on tendon biomechanical integrity