Pulsed electromagnetic field (PEMF) has been shown to increase bone mineral 
density in osteoporosis patients and prevent bone loss in ovariectomized rats. 
But the mechanisms through which PEMF elicits these favorable biological 
responses are still not fully understood. Receptor activator of nuclear factor 
κB ligand (RANKL) and osteoprotegerin (OPG) are cytokines predominantly secreted 
by osteoblasts and play a central role in differentiation and functional 
activation of osteoclasts. The purpose of this study was to investigate the 
effects of PEMF on RANKL and OPG expression in ovariectomized rats. Thirty 
3-month-old female Sprague-Dawley rats were randomly divided into three groups: 
sham-operated control (Sham), ovariectomy control (OVX), and ovariectomy with 
PEMF treatment (PEMF). After 12-week interventions, the results showed that PEMF 
increased serum 17β-estradiol level, reduced serum tartrate-resistant acid 
phosphatase level, increased bone mineral density, and inhibited deterioration 
of bone microarchitecture and strength in OVX rats. Furthermore, PEMF could 
suppress RANKL expression and improve OPG expression in bone marrow cells of OVX 
rats. In conclusion, this study suggests that PEMF can prevent 
ovariectomy-induced bone loss through regulating the expression of RANKL and 
OPG.