BoneKEy Reports | BoneKEy Watch
PTH therapy for hypoparathyroidism impacts bone structure
DOI:10.1038/bonekey.2012.125
In this study, 62 patients with hypoparathyroidism (hypoPT) were randomized into two groups and given either parathyroid hormone (PTH [1–84]) substitution therapy in addition to vitamin D analogues and calcium supplements, or a placebo. Iliac crest biopsies taken at 24 weeks showed a 27% reduction in trabecular thickness and a 4% reduction in trabecular bone density in PTH-treated patients compared with controls.
Just under half of the PTH-treated patients showed evidence of trabecular tunneling, and this subgroup exhibited increased levels of markers of bone resorption and formation. In general, PTH-treated subjects showed a 139% increase in the density of Haversian canals, which increased cortical porosity, but the difference between treated and untreated patients did not reach significance (P=0.09).
Further investigations revealed a significant reduction (1–4%) in areal and volumetric bone mineral density (BMD) in different hip regions in PTH-treated patients compared with controls; areal BMD also decreased by 1.8% (P<0.05) at the lumbar spine but volumetric BMD at this site increased by 12.8% (P=0.02).
Editor's comment: PTH administration is emerging as a new potential therapeutic approach for patients with hypoPT. The analysis of iliac crest biopsies/bone turnover indices in these patients is crucial if we are to understand the effects of PTH replacement therapy on renewed bone remodeling. An interesting corollary is the demonstration that the apparent increase in cortical porosity is due to a higher density of Haversian canals, i.e. not necessarily a sign of cortical weakening.
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