Effect of estrogen on tendon collagen synthesis, tendon structural characteristics, and biomechanical properties in postmenopausal women.
Level 3 - non-randomized controlled study
Non-randomized controlled cross-sectional comparative physiological study
PubMed 18927264 · doi:10.1152/japplphysiol.90935.2008
What was done
Researchers studied 20 postmenopausal women divided into habitual users of oral estradiol replacement therapy (ERT, n = 10) and nonusers (control, n = 10) at rest and following acute one-legged resistance exercise. Tendon collagen synthesis was assessed using stable isotope incorporation (fractional synthesis rate, FSR) and microdialysis for NH(2)-terminal propeptide of type I collagen. Tendon morphology and ultrastructure were measured via MRI and transmission electron microscopy, while tendon biomechanics (including Young's modulus) were measured using ultrasound during isometric maximal voluntary contractions.
What was found
Tendon FSR was significantly higher in ERT users compared to controls (P < 0.001), but type I collagen propeptide synthesis did not differ between groups (P = 0.32). In ERT users, serum estradiol correlated positively with resting tendon synthesis, whereas the synthesis change from rest to exercise correlated negatively with serum estradiol. Groups did not differ in tendon area, fibril density, fibril volume fraction, or fibril mean area. ERT users had a significantly higher percentage of medium-sized fibrils (P < 0.05) and a lower Young's modulus (P < 0.05), while the percentage of large fibrils tended to be greater in controls (P = 0.10). Absolute values and effect sizes were not reported in the abstract.
Why it matters
The findings show that exogenous estrogen in postmenopausal women modulates connective tissue homeostasis by increasing baseline collagen turnover, shifting collagen fibril diameter distribution, and altering mechanical stiffness.
Limits
The study evaluated a very small sample (n = 10 per group) without randomized allocation, leaving room for baseline confounding. The abstract does not provide exact numerical values, effect sizes, or clinical injury outcomes.
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