PF4 and osteoporosis: Moreover, the nonspecific binding between LMWHs and macrophages, endothelial cells, osteoblasts, plasma proteins, platelets and platelet factor 4 (PF4) can reduce the incidence of heparin-related adverse reactions, such as heparin induced thrombocytopenia (HIT), osteoporosis, and heparin-induced bleeding [14].