Bone Histomorphometry in Hypoparathyroidism
Analysis of the iliac crest bone biopsy by histomorphometric analysis and microcomputed tomography has shed new insight on the cellular and structural skeletal abnormalities in hypoparathyroidism. The disease is characterized by increased bone mass in both cancellous and cortical compartments with increased cortical and trabecular thickness. These changes are accompanied by reduced activation frequency of bone remodeling with a positive bone balance in each remodeling cycle. Treatment with PTH reverses some of these abnormalities, increasing remodeling activation frequency and reducing cortical bone mass by increasing porosity and decreasing trabecular thickness by stimulating intra-trabecular tunneling. Cancellous bone volume remains constant in adults but is further increased by treatment with PTH in adolescents. Mathematical modeling, based on real biopsy samples, suggests that, in addition to reduced remodeling activation frequency, the hypoparathyroid state leads to increased osteocyte mechanosensitivity, which results in a marked increase in bone formation early in the disease process.
KeywordsHypoparathyroidism Bone Histomorphometry Microcomputed tomography Biopsy PTH
I wish to acknowledge the seminal contributions of my colleagues and collaborators in the studies reviewed in this chapter, in particular Drs. John Bilezikian, Michaela Rubin, and Hua Zhou.
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