**3.3 Osteoporosis in children**

In addition to adults, the risk of developing osteoporosis or having bone fractures is also important in younger patients.

For girls between 11 and 13 years old and boys between 13 and 15 years old, the occurrence of fractures is totally normal. Indeed, bone grows rapidly before the attainment of the peak bone mineral density; thus, during puberty, bone is undermineralized, which explains the occurrence of fractures in this period independent of developing any bone disease [23, 24]. However, repeated fractures in early age could be one of the causes inducing osteoporosis and the occurrence of frequent fractures in future. In addition to osteoporosis in children, the decrease of BMD can be related to the appearance of some chronic diseases suchlike cerebral palsy and celiac disease [25] or undergoing treatments such as chemotherapy used for children with lymphoblastic leukemia cancer [26, 27].

As shown before, in women's case, estrogen level is one of the biggest promoters of the bone formation phase in the remodeling process. Estrogen level increases due to its secretion by ovaries during the puberty phase for girls, while it circulates in low concentration for boys and girls before their sexual maturity. Thus, the augmentation of estrogen induces longitudinal bone growth during the puberty period [28]. However, a disturbance of estrogen levels could cause critical bone problems as shown by [29], who found that decreasing concentration of estrogen for girls could induce a sideways curvature of the spine known as scoliosis disease.
