Low forearm bone density as a clue to suspect primary hyperparathyroidism in postmenopausal women with osteoporosis:...

Brief rationale: To evaluate the utility of forearm-DXA in differentiating postmenopausal osteoporosis and to explore its relationship with clinical features of PHPT.

Forearm-DXA was useful for differential diagnosis and independently associated with calcium in PHPT. Significance of the paper: This is the first study demonstrating these findings.

To evaluate the utility of forearm dual-energy X-ray absorptiometry (DXA) measurement in differentiating primary postmenopausal osteoporosis from primary hyperparathyroidism (PHPT) related osteoporosis and to examine its association with clinical features of PHPT.

This retrospective study included 246 women with PHPT (153 postmenopausal and 93 premenopausal) and 100 postmenopausal controls with osteopenia/osteoporosis. DXA measurements of the lumbar spine, hip, and one-third distal radius, together with clinical and biochemical data, were compared between postmenopausal patients with PHPT and controls, as well as between postmenopausal and premenopausal PHPT groups. Associations between DXA measurements and clinical findings were also analyzed in PHPT.

Postmenopausal PHPT and controls were matched for age and body-mass index (BMI), osteoporosis was more frequent in PHPT (p = 0.001), with the distal radius most affected (p < 0.001). Multivariate regression confirmed an independent association between distal radius T-scores and PHPT [OR 1.88, 95% CI: 1.44-2.47]. In postmenopausal patients with osteoporosis by lumbar spine or hip DXA, ROC analysis showed that distal radius scores had excellent discriminatory value (AUC > 0.80) for differentiating PHPT from primary postmenopausal osteoporosis; optimal cutoffs were T-score < -2.4 (80.0% sensitivity, 63.6% specificity) and Z-score < -1.0 (81.5% sensitivity, 63.6% specificity). In premenopausal PHPT, calcium was independently associated with the distal radius T-score [(B = -0.594 (95% CI: -1.027 to -0.160)].

This is the first study to show the utility of forearm DXA in differentiating primary postmenopausal osteoporosis from PHPT-related osteoporosis as well as its independent association with calcium in PHPT. Although the diagnosis of PHPT is primarily biochemical, a predominant reduction in distal radius BMD should prompt evaluation for a parathyroid disorder. Moreover, our data may provide clues to help distinguish whether osteoporosis-identified as a surgical indication in PHPT-observed in postmenopausal individuals with PHPT is primarily attributable to PHPT or to menopause.