APLN and osteoporosis: In addition, PINP, an osteoblast-derived protein, is one biological response marker during treatment for osteoporosis.13 At the same time, ICTP, as a specific component of type I collagen, generates from damaged mature bone matrix, and can represent a sensitive indicator of bone resorption in vivo.14 Subsequently, in the current study we evaluate the relation between Apelin-13, ICTP and PINP to detect the influence of Apelin-13 on osteoporosis.