CLINICAL STUDY Changes in bone density and bone markers in rhythmic gymnasts and ballet dancers: implications for puberty and leptin levels Marı ´a Teresa Mun ˜ oz, Concepcio ´n de la Piedra 1 , Vicente Barrios, Guadalupe Garrido 2 and Jesu ´ s Argente Servicio de Endocrinologı ´a, Hospital Infantil Universitario Nin ˜o Jesu ´s, Madrid, Spain, 1 Laboratorio de Bioquı ´mica, Seccio ´n de Fisiopatologı ´a O ´ sea, Fundacio ´n Jime ´nez Dı ´az, Madrid, Spain and 2 Instituto Nacional de Educacio ´n Fı ´sica, Departamento de Rendimiento Humano, Madrid, Spain (Correspondence should be addressed to M T Mun ˜oz Calvo, Servicio de Endocrinologı ´a, Hospital Infantil Universitario Nin ˜o Jesu ´s, Avda Mene ´ndez Pelayo, 65, 28009 Madrid, Spain; Email: munozmaite@yahoo.es) Abstract Objective: Our aim was to compare physical activity and biochemical markers with bone mineral acquisition in rhythmic gymnasts and ballet dancers. Methods: Weight, height, body mass index, nutritional intake, bone age and menstrual histories were analyzed in nine rhythmic gymnasts, twelve ballet dancers and fourteen controls. Bone mineral den- sity (BMD) was assessed by X-ray absorptiometry at the lumbar spine, hip and radius. Bone alkaline phosphatase (bAP) and amino-terminal propeptide of procollagen I (PNIP) in serum and urinary a-isomer of the carboxy-terminal telopeptide of collagen I (a-CTX) were measured. Results: Bone age was delayed 2 years and mean age at menarche was 15^0.9 years in rhythmic gymnasts and 13.7^1 years in ballet dancers, compared with 12.5^1 years in controls. Trocanteric and femoral neck BMD was significantly higher in rhythmic gymnasts compared with ballet dancers and controls. Right forearm (non-loaded zone) BMD was significantly decreased in rhythmic gym- nasts and ballet dancers compared with controls. All subjects had normal bAP and PNIP levels, but the a-CTX/creatinine (Cr) ratio was increased in rhythmic gymnasts (P , 0.001) with an inverse correlation between right forearm BMD and the a-CTX/Cr ratio (r ¼ 2 0.74, P , 0.001). Serum leptin levels were decreased in rhythmic gymnasts and ballet dancers. Rhythmic gymnasts had a posi- tive correlation between right forearm BMD and leptin levels (r ¼ 0.85, P , 0.001). Conclusions: Decreased bone mass in rhythmic gymnasts could be partially explained by an increase in bone resorption. Serum leptin levels could be implicated in the pubertal delay and be a good marker of bone mass in these subjects. European Journal of Endocrinology 151 491–496 Introduction Bone mineral density (BMD) is modified by environmen- tal factors such as exercise and dietary calcium intake. Several cross-sectional studies have shown that high impact weight-bearing activity is beneficial for the load-bearing sites of the skeleton (1, 2). An increase in bone mass due to augmentation of bone size, density of skeletal areas and bone turnover has been demonstrated in adolescents performing intensive exercise. Indeed strategies that enhance the acquisition of bone mass may be protective against osteoporosis (3). Growth during puberty depends on genetic potential, nutritional status and hormonal regulation. Energy expenditure may modify the effects of these three fac- tors on linear growth rate and the relative proportions of lean and fat body mass (4). In high-performance female gymnasts, a low body fat mass is favored for the esthetic appeal currently required for the complex movements performed. Optimal nutritional intake rela- tive to physical training regimes is essential for normal pubertal development (5). Hence, this could be a pro- blem in adolescents with strenuous training programs while trying to maintain a lean figure. Although a high degree of exercise-induced osteope- nia and amenorrhea are frequently found in elite ath- letes and performers, some studies suggest that the low estrogen levels may not be the cause of the low bone mass in these women (6). As bone mass is the net result of bone formation and resorption, an uncoupling between these two activities may be the cause of the osteopenia found in young athletes. Biochemical mar- kers of bone remodeling can be used to determine the degree of bone formation and resorption. The number of such bone markers has expanded greatly during recent years. In a previous study, we demonstrate that European Journal of Endocrinology (2004) 151 491–496 ISSN 0804-4643 q 2004 Society of the European Journal of Endocrinology Online version via http://www.eje.org