Gender differences in bone turnover in 2-year-old Thoroughbreds.
BACKGROUND
Injuries to the skeleton are a major cause of morbidity and mortality in racehorses and age, gender and season have all been shown to influence risk of injury.


OBJECTIVE
To use biochemical markers of bone cell activity to establish to whether cellular processes in bone underlie these described effects.


METHODS
Blood samples were collected monthly from 2-year-old horses in race training between November 1998 and September 1999. Mean age at the start of the study was 20 months (range 18-23 months), with no significant difference in average age between colts (n = 84) and fillies (n = 63). Three markers were measured; osteocalcin (OC, bone formation), the carboxyterminal cross-linked telopeptide of type I collagen (ICTP, bone resorption) and the carboxyterminal propeptide of type I collagen (PICP), which is less 'bone-specific' than the other 2 markers.


RESULTS
Colts had, on average, 3.62 ng/ml higher OC concentrations (P = 0.044) and 0.68 mg/l higher ICTP concentrations (P = 0.01) than fillies. The effect of gender was not statistically significant for PICP. However, in May, PICP concentrations were on average 157 mg/l higher in fillies than colts. There was no effect of age or season on marker concentrations.


CONCLUSIONS
This study has shown that there are gender differences in bone turnover markers in 2-year-old Thoroughbreds; however, age, within the limited range studied, did not have a significant effect on bone cell activity. Lower bone marker concentrations may reflect smaller bone size and/or earlier skeletal maturation in fillies. An increase in concentrations of PICP in fillies in spring and early summer may relect an influence of sex hormones on collagen turnover.


CONCLUSIONS
Gender differences in bone cell activity in 2-year-old colts and fillies may influence bone's adaptive responses to training and risk of injury.
Jackson
B F
BF
Department of Veterinary Basic Sciences, The Royal Veterinary College, London NW1 0TU.
Lonnell
C
C
Verheyen
K
K
Wood
J L N
JL
Pfeiffert
D U
DU
Price
J S
JS
D000367:Age Factors; D000818:Animals; D015415:Biomarkers / Q000097:blood; D001846:Bone Development / Q000502:physiology; D016723:Bone Remodeling / Q000502:physiology; D001862:Bone Resorption / Q000097:blood / Q000662:veterinary; D001842:Bone and Bones / Q000378:metabolism*; D024042:Collagen Type I; D005260:Female; D006736:Horses / Q000097:blood / Q000378:metabolism*; D008297:Male; D015675:Osteocalcin / Q000097:blood*; D010012:Osteogenesis / Q000502:physiology; D010446:Peptide Fragments / Q000097:blood*; D010455:Peptides; D011347:Procollagen / Q000097:blood*; D012621:Seasons; D012737:Sex Factors
D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C042813:procollagen type I carboxy terminal peptide; D015675:Osteocalcin