Sympathetic tone regulation of bone homeostasis begins when leptin, a hormone that is mainly secreted by adipocytes, which stimulates sympathetic outflow and neurotransmitter secretion.40 Although fat accumulation at the necrotic regions of the femoral head is also related to GC-induced osteonecrosis,7 serum leptin levels showed no significant change in the MPS-treated mice compared to the vehicle-treated mice, as demonstrated by ELISA (Fig. S3d). The gene discussed is LEP; the disease is osteonecrosis.