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.

Objective: Glucocorticoid (GC) therapy is associated with adverse effects on bone metabolism, yet the effects of different GC physiological replacement regimens in hypopituitarism are not well characterised. We aimed to assess the effect of three hydrocortisone (HC) replacement dose regimens on bone turnover. Study design: An open cross-over study randomising ten hypopituitary men with severe ACTH deficiency to three commonly used HC dose regimens: dose A (20 mg mane and 10 mg tarde), dose B (10 mg mane and 10 mg tarde) and dose C (10 mg mane and 5 mg tarde). Methods: Following 6 weeks of each regimen, the participants underwent 24-h serum cortisol sampling and measurement of bone turnover markers: bone-specific alkaline phosphatase, procollagen type I N-propeptide (PINP), intact osteocalcin (OC(1-49)), C-terminal cross-linking telopeptide (CTX-I) and tartrate-resistant acid phosphatase 5b (TRACP5b). Bone remodelling balance was estimated as an absolute ratio (PINP:CTX-I) and as an index using standardised scores derived from the matched controls. Results: There were significant increases in the concentrations of the formation markers PINP (PZ0.045) and OC(1-49) (PZ0.006) and in the PINP:CTX-I ratio (PZ0.015), and a more positive bone remodelling balance index (PZ0.03) was observed in patients on the lowest dose C than in those on the highest dose A. Mean 24-h cortisol concentrations correlated negatively with CTX-I (rZK0.66 and PZ0.04) and TRACP5b (rZK0.74 and PZ0.01) in patients on dose B and with OC(1-49) (rZK0.66 and PZ0.04) and CTX-I (rZK0.81 and P!0.01) in patients on dose C. In patients receiving the lower-dose regimen, trough cortisol concentrations correlated with increased bone formation and resorption. Conclusion: Low-dose HC replacement (10 mg mane and 5 mg tarde) is associated with increased bone formation and a positive bone remodelling balance. This may have a long-term beneficial effect on bone health.

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Background Glucocorticoid therapy is the most common cause of iatrogenic osteoporosis. Less is known regarding the effect of glucocorticoids when used as replacement therapy on bone remodelling in patients with adrenal insufficiency. Enhanced intracellular conversion of inactive cortisone to active cortisol, by 11 beta-hydroxysteroid dehydrogenase type 1(11β-HSD1) and other enzymes leading to alterations in glucocorticoid metabolism, may contribute to a deleterious effect on bone health in this patient group. Methods Study design: An open crossover prospective study randomizing ten hypopituitary men, with severe ACTH deficiency, to three commonly used hydrocortisone dose regimens. Measurements: Following 6 weeks of each regimen, patients underwent 24-h serum cortisol/cortisone sampling, measurement of bone turnover markers, and a 24-h urine collection for measurement of urinary steroid metabolites by gas chromatography-mass spectrometry (GC-MS). Serum cortisone and cortisol were analysed by liquid chromatography-mass spectrometry (LC-MS). Results Dose-related and circadian variations in serum cortisone were seen to parallel those for cortisol, indicating conversion of ingested hydrocortisone to cortisone. The median area under the curve (AUC) of serum cortisone was significantly higher in patients on dose A (20 mg/10 mg) [670.5 (IQR 621–809.2)] compared to those on dose C (10 mg/5 mg) [562.8 (IQR 520.1–619.6), p = 0.01]. A negative correlation was observed between serum cortisone and bone formation markers, OC [1–49] (r = − 0.42, p = 0.03), and PINP (r = − 0.49, p = 0.01). There was a negative correlation between the AUC of night-time serum cortisone levels with the bone formation marker, OC [1–49] (r = − 0.41, p = 0.03) but there were no significant correlations between day-time serum cortisone or cortisol with bone turnover markers. There was a negative correlation between total urinary cortisol metabolites and the bone formation markers, PINP (r = − 0.39, p = 0.04), and OC [1–49] (r = − 0.35, p = 0.06). Conclusion Serum cortisol and cortisone and total urinary corticosteroid metabolites are negatively associated with bone turnover markers in patients receiving replacement doses of hydrocortisone, with nocturnal glucocorticoid exposure having a potentially greater influence on bone turnover. Trial registration Irish Medicines Board Clinical Trial Number – CT900/459/1 and EudraCT Number – 2007-005018-37. Registration date: 07-09-2007.