[Bone mineral density in primary hyperparathyroidism]

Skeletal complications of advanced hyperparathyroidism include clinically bone pains, muscle weakness, bone deformities and fractures. X-ray studies reveal subperiosteal bone resorption, atrophy of the cortex of long bones, cysts, brown tumours and calcifications of soft tissues; these changes appear in the late period of the disease. In recent onset of hyperparathyroidism bone changes may be detected by X-ray absorptiometry. Thus the aim of our study was to evaluate bone mineral density with the use of dual energy X-ray absorptiometry (DEXA) at two sites: in lumbar vertebral bodies consisting mainly of the trabecular bone and in 1/3 distal part of the radius composed predominantly of the cortical bone. Twenty-three patients with primary hyperparathyroidism were included in our study. Hypercalcemia (ionized calcium above 5.4 mg/100 ml, total calcium above 10.6 mg/100 ml) and increased serum PTH, above 100 pg/ml, were detected in all patients. Isotope scintigraphy using 99mTc-MIBI revealed the presence of a parathyroid adenoma; this was confirmed at surgery and histopathologically. In bone densitometry we found greatly reduced bone mineral density (BMD) in 1/3 distal part of the radius amounting to 66.8 +/- 12.0% of the age-matched range and markedly smaller bone loss in lumbar spine, BMD was 91.7 +/- 14.6%. In 10 patients control densitometry, performed 6-24 months after parathyroid adenomectomy, revealed a marked 10 to 22% increase in bone density of lumbar vertebral bodies in the first year. BMD of the 1/3 distal part of the radius increased to a smaller degree 6.3% per year.

1. Bone densitometry in primary hyperparathyroidism reveals pronounced decrease in bone mineral density in the 1/3 distal part of the radius and much smaller decrease of the lumbar spine density. 2. Parathyroid adenomectomy leads to a rapid increase in density of the trabecular bone L1-L4 vertebral bodies and much smaller increase in the cortical bone of the radius. 3. Pronounced differences in bone mineral density of cortical bone and trabecular bone surpassing 20% are characteristic of hyperparathyroidism as they do not occur in other types of osteoporosis.