The natural history and hip geometric changes of primary hyperparathyroidism without parathyroid surgery

There have been few reports on changes in bone geometry in asymptomatic patients with primary hyperparathyroidism (PHPT) not treated surgically. We reviewed the records concerning biochemical parameters, bone mineral density (BMD), and hip geometry in 119 PHPT patients who did not undergo parathyroidectomy, followed up at one of three hospitals affiliated to Seoul National University from 1997 to 2013. We examined biochemical parameters over 7 years and BMD and hip geometry over 5 years of follow-up. We further compared hip geometry and BMD derived from dual-energy X-ray absorptiometry (DXA) between patients and age- and sex-matched controls. The median follow-up duration of 56 patients for whom surgery was not indicated was 33.9 months (range 11.2-131.2 months), and 19.6 % of these patients had disease progression during follow-up. Serum calcium levels remained stable for 7 years in all 119 patients. From a comparison of the PHPT patients for whom surgery was not indicated with controls, both male and postmenopausal female patients had significantly lower hip axis length (P < 0.001), cross-sectional moment of inertia (P < 0.001), cross-sectional area (P < 0.001), and section modulus (P < 0.001). In addition, cortical thickness was significantly decreased at 5 years compared with individual baseline values (P = 0.003). However, there was no significant change in BMD for the duration of the 5-year follow-up. DXA-derived geometry can detect skeletal change in asymptomatic PHPT patients for whom surgery is not indicated, supporting the concept that even mild PHPT can eventually compromise the cortical bones. Hip geometry is a potential tool for monitoring skeletal complication in asymptomatic PHPT patients.