Age-related changes in serum insulin-like growth factor-I, insulin-like growth factor-I binding protein-3 and articular cartilage structure in Thoroughbred horses.
Authors: Fortier L A, Kornatowski M A, Mohammed H O, Jordan M T, O'Cain L C, Stevens W B
Journal: Equine veterinary journal
Summary
# Editorial Summary Understanding the structural maturation of articular cartilage through growth and development has proven difficult to characterise in horses, yet this knowledge is essential for clinicians and researchers working with young stock and interpreting developmental orthopaedic disease. Fortier and colleagues measured serum insulin-like growth factor-I (IGF-I) and its binding protein-3 (IGFBP-3) across Thoroughbred horses aged 9 to 715 days, then correlated these endocrine markers with histological examination of osteochondral tissue from animals aged 4 to 28 months to identify structural cartilage changes. Peak IGF-I and IGFBP-3 concentrations occurred at approximately 225 days in both sexes, marking the onset of puberty and corresponding to the point at which cartilage canals disappeared from articular cartilage; concentrations subsequently declined to steady-state levels by 450 days, which aligned with initial tidemark formation—indicating the transition from pubescent to post-pubescent ageing. These findings establish that the window of pubescence spans roughly 225–450 days of age in Thoroughbreds, with the completion of skeletal maturation at around 15 months. For practitioners, these data provide a practical framework for distinguishing normal developmental changes from pathological responses, enable more targeted monitoring of young horses' growth trajectories, and offer a baseline against which abnormal IGF-I elevation from disease or therapeutic intervention can be assessed.
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Practical Takeaways
- •Horses can be classified as pubescent from 225–450 days (7.5–15 months) and post-pubescent/ageing after 450 days; this framework helps identify appropriate cohorts for developmental studies and age-related research
- •Abnormally elevated serum IGF-I concentrations in horses beyond 450 days may warrant investigation for underlying disease or inappropriate growth hormone administration
- •Structural cartilage changes (canal closure and tidemark formation) provide objective markers of skeletal maturity that correlate with hormonal transitions during growth
Key Findings
- •Serum IGF-I and IGFBP-3 concentrations peak at approximately 225 days of age in both male and female horses, marking the onset of puberty
- •Cartilage canals disappear from articular cartilage just before the 225-day peak in IGF-I/IGFBP-3 concentrations
- •IGF-I and IGFBP-3 concentrations decline to steady-state levels by approximately 450 days of age, signalling exit from puberty and beginning of skeletal maturity
- •Tidemark formation in osteochondral tissue correlates with IGF-I/IGFBP-3 steady-state at 450 days, establishing a structural marker for skeletal maturity