**1. Introduction**

Bone quality depends on the structural and material properties of the bone. By increased mortality and healthcare costs due to bone fractures, bone fragility becomes a major health concern [1]. In order to assess bone fragility, the integration of quantity, quality, and turnover of bone factors is necessary. The BMD, quantified using the clinical imaging technique called X-ray radiography, namely, the dual-energy X-ray absorptiometry (DXA), is one of the most important bone factors reflecting the quality of bone in terms of quantity to assess bone fracture risk in osteoporotic patients [2]. Osteoporosis is a biochemical problem characterized by a decrease in bone mass, a deterioration and an alteration of bone tissue microarchitecture, which increases the risk of fractures. Old bone fracture, oxidative stress, age, and menopause are among the main causes of osteoporosis. Giving its various causes, osteoporosis could affect any gender at any age. For women and men, for example, osteoporosis is associated with aging and more specifically, for women, with hormonal deficiency caused by menopause [3]. Meanwhile for children, BMD loss is generally related to diseases' or treatments' use.

A wide variety of diseases and treatments containing toxic agents for bone cause or contribute to osteoporosis development [4]. In this chapter, we will discuss the diseases and treatments inducing BMD abnormal loss or gain and report different studies' findings concerning diseases and treatment association with osteoporosis. Our work would be subdivided into three main parts: (i) BMD generalities; (ii) osteoporosis in women, men, and children; and (iii) diseases and clinical interventions to limit osteoporosis development.
