PRIMARY HYPERPARATHYROIDISM AND OSTEOPOROSIS

Primary hyperparathyroidism (PHPT) is considered a cause of secondary osteoporosis as a consequence of its known catabolic effect promoting osteoclast activity and bone resorption. However, recent in vitro and in vivo studies have shown that parathyroid hormone (PTH) may also hav e an anabolic effect on the mammalian skeleton. These two paradoxical effects of parathyroid hormone are discussed in the light of recent re sults of basic research, and of bone densitometric and histomorphometr ic data collected in patients affected by PHPT. Review of the literatu re leads to the conclusion that in PHPT skeletal damage involves preva lently cortical bone, while the mineral content of trabecular bone is preserved or even increased. On the basis of bone mineral density (BMD ) measurements, osteoporosis prevalence in the early postmenopausal pe riod seems to be significantly higher in women affected by PHPT than i n the general population. As age progresses, osteoporosis prevalence s eems to decrease in PHPT, while it increases exponentially with age in the general population. Similarly in (PHPT) vertebral and appendicula r fractures occur prevalently in the earlier decades of life with a hi gher frequency than in normal subjects, while with advancing age the f racture incidence becomes equal to that of the general population. whe n bone density is measured in lateral projection at lumbar level, BMD values in patients with mild asymptomatic PHPT are significantly highe r than in controls. We conclude that PTH hypersecretion may represent a risk factor for osteoporosis and fractures in the young and in the e arly postmenopausal period, while it may have a protective effect on t rabecular bone in elderly postmenopausal women. (C) 1998, Editrice Kur tis.