An altered hormonal profile and elevated rate of bone loss are associated with low bone mass in professional horse-racing jockeys

• Published in: Journal of bone and mineral metabolism Vol. 30; no. 5; pp. 534 - 542
• Main Authors: Dolan, Eimear, McGoldrick, Adrian, Davenport, Colin, Kelleher, Grainne, Byrne, Brendan, Tormey, William, Smith, Diarmuid, Warrington, Giles D.
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01.09.2012; Springer; Springer Nature B.V
• Subjects: Absorptiometry, Photon - methods; Adult; Animals; Athletes; Biological and medical sciences; Body Composition - physiology; Body Mass Index; Bone Density - physiology; Bone Resorption - blood; Bone Resorption - metabolism; Bone Resorption - pathology; Bone Resorption - urine; Creatinine - urine; Diseases of the osteoarticular system; Femur Neck - metabolism; Femur Neck - pathology; Hormones - metabolism; Horses; Humans; Insulin-Like Growth Factor I - metabolism; Male; Medical sciences; Medicine; Medicine & Public Health; Metabolic Diseases; Original Article; Orthopedics; Osteogenesis - physiology; Osteoporosis. Osteomalacia. Paget disease; Sex Hormone-Binding Globulin - metabolism; Sports; Testosterone - blood; Young Adult; Energy restriction; Testosterone; Bone; Jockeys; Diseases of the osteoarticular system; Rheumatology; Vertebrata; Mammalia; Bone mass; Animal; Horse; Perissodactyla; Ungulata; Osteopenia
• ISSN: 0914-8779; 1435-5604
• DOI: 10.1007/s00774-012-0354-4

Horse-racing jockeys are a group of weight-restricted athletes, who have been suggested as undertaking rapid and extreme weight cycling practices in order to comply with stipulated body-mass standards. The aim of this study was to examine bone mass, turnover and endocrine function in jockeys and to compare this group with age, gender and body mass index matched controls. Twenty male professional jockeys and 20 healthy male controls participated. Dual energy X-ray absorptiometry scans and early morning fasting blood and urine samples were used to measure bone mass, turnover and a hormonal profile. Total body bone mineral density (BMD) was significantly lower in jockeys (1.143 ± 0.05 vs. 1.27 ± 0.06 g cm −3 , p  < 0.01). Bone resorptive activity was elevated in the jockey group as indicated by significantly higher urinary NTx/creatinine (76.94 ± 29.52 vs. 55.9 ± 13.9 nmol mmol −1 , p  < 0.01), resulting in a significantly negative uncoupling index between bone resorption and formation. Sex hormone binding globulin (SHBG) levels were significantly higher in jockeys (41.21 ± 9.77 vs. 28.24 ± 9.98 nmol L −1 , p  < 0.01) with a lower percentage of bioavailable testosterone (48.89 ± 7.38 vs. 59.18 ± 6.74 %, p  < 0.01). SHBG and insulin-like growth factor-1 were independent predictors of total body and femoral neck BMD, respectively ( p  < 0.05). In conclusion, it appears that professional jockeys have an elevated rate of bone loss and reduced bone mass that appears to be associated with disrupted hormonal activity. It is likely that this may have occurred in response to the chronic weight cycling habitually experienced by this group.