Factors influencing bone mineral density in hyperparathyroidism phenotypes: a prospective study

Primary hyperparathyroidism (PHPT) is a condition recognized to include distinct biochemical phenotypes: hypercalcemic, normocalcemic, and normohormonal PHPT. This condition is characterized by inappropriately elevated parathyroid hormone (PTH) levels relative to serum calcium levels, leading to high bone turnover and decreased bone mineral density (BMD). Although BMD has been shown to improve following curative parathyroidectomy (PTX), there is limited data on the relationship between BMD changes after PTX and according to the clinical phenotypes of PHPT. This prospective study aims to identify the best candidates for surgery among these three phenotypes of PHPT by examining symptoms and comorbidities, biochemical results, and both pre- and post-operative DXA scans.

This is a prospective single-center study including 104 consecutive patients who underwent PTX for PHPT. Sociodemographic profiles and biochemical results were collected at both pre- and at 6 months post-surgery. All patients underwent dual-energy x-ray absorptiometry (DXA) scans at 1 and 6 months before surgery, and again between 12 and 18 months after surgery, to assess and compare changes in bone mineral density (BMD). Patients were categorized into three subgroups (normohormonal, hyperparathyroid normocalcemic and hyperparathyroid hypercalcemic) to assess differences in BMD improvement across these groups.

According to predefined thresholds, 40.0% of patients experienced a significant BMD gain at the spine, 35.1% at the femur, 23.5% at the left hip, and 8.6% at the radius. Additionally, a greater postoperative drop in PTH was associated with larger BMD gains at the spine (SD 0.07; mean 0.03) and left femur bone (SD 0.06; mean 0.02). There was no significant change in T-score at the one-third radius. Higher preoperative urinary calcium level was associated with greater BMD and T-score improvement at the left hip. All PHPT phenotypes demonstrated similar postoperative BMD gains. No differences in BMD improvement were observed between males and females, nor was there any correlation between BMD gains and age.

Our findings suggest that BMD improves in all PHPT patients undergoing curative PTX, irrespective of clinical phenotype, age or sex. While patients with more severe biochemical profiles exhibited greater increases in BMD and T-scores, milder forms showed favorable trends that require confirmation in larger studies.