Primary prevention of osteoporosis must aim at increasing bone mass acquisition before late adolescence. During pubertal years both genders reach peak bone acquisition, though males develop a greater skeletal mass. This dimorphism is largely regulated by endocrine factors, with critical roles played by gonadal steroids, growth hormone and insulin growth factor-1, amongst the most important. Menstrual history is a surrogate for the adequacy of hormonal functioning, nutrition and physical activity that may be a marker of bone status and development in young women. Adequate levels of adrenal, reproductive and pituitary hormones, growth factors and leptin are needed for the initiation and maintenance of regular menstrual cycles as well as for the achievement of peak bone mass. Adequate regular exercise and body composition are also pivotal elements in maintaining normal mechanical bone stimulus during bone growth. Avoidance of carbonated soft drink consumption, or excessive alcohol and any tobacco should be considered as these may interfere reaching adequate bone mass.