ABSTRACT
Melatonin (Mel), known as N-acetyl-5-methoxytryptamine chemically, is secreted not only by pineal gland but also by retina, gastrointestinal tract, and bone marrow (Sánchez-Barceló et al. 2010) and plays in many physiological processes as a regulatory role as well as bone metabolism (Cardinali et al. 2003; Gitto et al. 2009). Bone remodeling is under the control of the function of osteoclasts and osteoblasts (Manolagas 2000). Parathyroid hormone (PTH), estradiol (E2), and growth hormone controlled the balance between the activities of these two types of cells (Manolagas 2000). Mel promotes bone formation and prevents bone degradation through the promotion of the osteoblast differentiation and activation and increases osteoprotegerin expression that prevents osteoclast differentiation and scavenging of the free radicals that are responsible for bone resorption (SánchezBarceló et al. 2010; Turgut et al. 2005) (Figure 42.1).
