PTH and osteoporosis: In a glucocorticoid-induced osteoporosis (GIO) rat model, IF (16–18 h of fasting per day for 90 consecutive days) demonstrated significant protective effects against bone loss.64 A 90-day administration of dexamethasone (DEX) resulted in significant declines in both BMD and BMC, along with substantial increases in serum levels of glucose, insulin, triglycerides, total cholesterol, parathyroid hormone (PTH), osteoprotegerin (OPG), and bone resorption markers including deoxypyridinoline (DPD), N-terminal telopeptide of type I collagen (NTX-1), and TRAP-5b.