Elsevier

Bone

Volume 26, Issue 5, May 2000, Pages 535-543
Bone

Original Articles
Primary hyperparathyroidism: bone structure, balance, and remodeling before and 3 years after surgical treatment

https://doi.org/10.1016/S8756-3282(00)00260-XGet rights and content

Abstract

In 19 patients with primary hyperparathyroidism (PHPT) (14 women and 5 men; age 53 ± 11 years, range 29–69 years), bone densitometry, biochemical markers of bone turnover, and iliac crest bone biopsies were obtained before and 3 years after successful surgical treatment. A significant increase in bone mineral content (BMC) was observed in both the lumbar spine (p < 0.001) and the proximal part of the distal forearm (p < 0.001), whereas the increase in BMC in the femoral neck was insignificant. Biochemical markers of bone formation (serum alkaline phosphatase, serum bone alkaline phosphatase and serum osteocalcin) and resorption (serum pyridinoline cross-linked telopeptide of type I collagen and urine N-telopeptide of type I collagen) all decreased following treatment. In cortical bone, relative cortical width increased following surgery (p < 0.05) and cortical porosity decreased (p < 0.01). No changes were observed in core width or cortical width. In cancellous bone, no significant changes were observed in any of the measured structural parameters. However, significant reductions in the extent of osteoid- (p < 0.01) and tetracycline-labeled surfaces (p < 0.001), and in bone formation rate (p < 0.001) and activation frequency (p < 0.001), were found. The numerical decrease in the extent of eroded surfaces did not reach significance (p = 0.057). No changes were observed in mineral appositional rate and adjusted appositional rate. The amount of bone resorbed (expressed as the resorption depth) and the amount of bone reformed (expressed as wall thickness) per remodeling cycle seemed unaffected by the treatment. Consequently, no effect on bone balance per remodeling cycle could be detected. The present study of PHPT patients showed that, within 3 years after surgery, BMC of both cancellous and cortical bone areas had increased. At the same time, bone turnover decreased markedly, as judged from biochemical as well as histomorphometric data, but no changes were seen in trabecular bone structure. In cortical bone, the relative cortical width increased and the cortical porosity decreased.

Introduction

Primary hyperparathyroidism (PHPT) leads to a substantial increase in bone remodeling.2, 8, 26, 37 The effect on bone volume and structure is more ambiguous. Several histomorphometric studies have indicated that PHPT protects the volume and architecture of trabecular bone against age-dependent bone loss and structural changes.6, 25, 26, 42 Conversely, densitometric studies have shown a slight loss in bone mineral at locations dominated by cancellous bone.2, 32 This may be explained, however, by the increase in bone turnover, leading to a reversible bone mineral loss due to increased remodeling space and decreased mean bone age.2 This concept is supported by the observation that bone mass returns toward normal after treatment.3 In contrasting to the findings in cancellous bone, substantial irreversible bone loss is seen in skeletal areas dominated by cortical bone such as the distal forearm.16, 33 Thus, different parts of the skeleton may react differently upon stimulation by parathyroid hormone (PTH).

The aim of the present study was to, during the course of 3 years, evaluate the effect of successful surgery for PHPT on changes in bone remodeling and balance and on changes in cancellous and cortical bone volume and structure.

Section snippets

Patients and methods

This is a cohort study with a follow-up after 3 years. The investigation included 19 patients with PHPT (14 women and 5 men; age 53 ± 11 years, range 29–69 years). The patients were a part of a previously described group of 30 patients operated on for PHPT.2 All patients were enrolled in a follow-up study on the effect of surgical treatment on bone remodeling and bone densitometry. Eleven of the 30 patients were later withdrawn from the study: 1 patient left the country and was lost to

Biochemistry

Key biochemical parameters from all 19 patients before and 3 years after surgical treatment are given in Table 1 with relevant reference intervals. As expected, we found a significant reduction (normalization) in serum calcium (p < 0.001) and a significant increase in serum phosphate (p < 0.001). Table 2 shows the biochemical markers of bone turnover in all 19 patients and gives separate data for the 14 women and 5 men. Formative markers (serum AP, serum bAP, and serum osteocalcin) as well as

Structural parameters

The structural parameters in cortical and cancellous bone in all 19 patients and in the subgroups of 14 women and 5 men before and 3 years after surgical treatment are presented in Table 4 (reference values in Table 6). In cortical bone relative cortical width increased (p < 0.05) in the whole group of 19 patients. Cortical porosity decreased both in the whole group of 19 patients (p < 0.01) and in the subgroup of 14 women (p < 0.01) after treatment. In cancellous bone, no significant changes

Discussion

The present study of PHPT patients demonstrates that, within 3 years after surgical treatment, BMC of both cancellous and cortical bone regions increased significantly. At the same time, bone turnover decreased markedly as judged by both biochemical bone markers and histomorphometric measurements. No changes were seen in trabecular bone volume or structure. However, in cortical bone, the relative cortical width increased and cortical porosity decreased. These changes were observed in both the

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