Intermittent parathyroid hormone (iPTH) is the only FDA-approved therapy for bone loss due to conditions
such as osteoporosis that increases bone formation by osteoblasts; all other therapies approved for osteoporosis block
bone resorption by osteoclasts. The anabolic effects of iPTH are likely due to a combination of multiple mechanisms,
including induction of immediate-early genes, increased expression and/or activity of essential osteoblast transcription
factors, and downregulation of anti-osteogenic proteins, such as sclerostin. In contrast, continuous administration of PTH
induces bone loss primarily due to up-regulation of RANKL expression and inhibition of osteoprotegerin expression.
Keywords: Anabolic, immediate-early genes, osteoblast, osteoprotegerin, PTH, RANKL, sclerostin, transcription factors
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