Effect of primary hyperparathyroidism on volumetric bone mineral density and bone geometry assessed by peripheral quantitative computed tomography in postmenopausal women.

Context: Primary hyperparathyroidism (PH) is characterized by inappropriate PTH elevation with or without hypercalcemia. Bone disease involves catabolic action at cortical sites, whereas cancellous sites and geometry might be relatively preserved.
Objective: Our objective was to examine the effect of PH on quantitative and qualitative bone characteristics using peripheral quantitative computed tomography at the tibia in postmenopausal women with PH and healthy controls.
Design and Setting: We conducted a cross-sectional study at a tertiary referral center.
Patients: Fifty-two postmenopausal women with PH and 56 healthy controls, comparable for age and anthropometric measures, participated.
Intervention: There was no intervention.
Main Outcome Measure: We assessed volumetric bone mineral density (vBMD), bone mineral content (BMC), cortical thickness, cortical and trabecular area, peri- and endosteal circumference, and polar stress strength index assessed by peripheral quantitative computed tomography of the left tibia at 4% (cancellous), 14% (transition zone), and 38% (cortical) from the distal end.
Results: At 4%, there was a significant decrease of trabecular BMC and vBMD (P < 0.001), effect particularly evident in hypercalcemic patients, whereas trabecular area was comparable. At 38%, cortical BMC (P < 0.01), vBMD (P < 0.01), area (P < 0.05), and thickness (P < 0.001) were reduced in the PH group, particularly in hypercalcemic patients. Endosteal circumference increased (P < 0.001), whereas periosteal circumference was comparable, indicating cancellization of cortical bone. At 14%, polar stress strength index was significantly decreased (P < 0.01) in hypercalcemic patients, indicating impairment of bone mechanical properties.
Conclusions: Normocalcemic PH is characterized by catabolic actions at both cortical and cancellous sites (38 and 4%, respectively), an effect accentuated in hypercalcemic patients. Cortical geometric properties are adversely affected even in normocalcemic patients, whereas trabecular properties are generally preserved.