Endocrine Abstracts

Background: Hyperthyroidism is widely known to be an important cause of secondary osteoporosis through the accelerated rate of bone turnover, while primary hyperparathyroidism is typically associated with loss of cortical bone and less so of trabecular bone, as seen on dual-energy x-ray absorptiometry (DXA). The evaluation of bone quality in these categories is not fully understood and needs further research. The aim of this study was to compare the bone quantity and quality, using bone turnover biomarkers, bone mineral density (BMD) and trabecular bone score (TBS) between patients with hyperthyroidism and primary hyperparathyroidism.

Methods: We performed a cross-sectional study on 52 patients evaluated in our clinic, between October 2018 and December 2019, 31 patients with hyperthyroidism (HT) and 21 patients with primary hyperparathyroidism (PHPT). The exclusion criteria were age <18 years, other secondary endocrine causes of osteoporosis. We analyzed demographic data, fragility fracture history, bone turnover markers, BMD and TBS.

Results: Among the 52 patients, the mean age was 58.1 ± 11.8 years, female was the dominant gender (94.2%) and the mean body mass index was 28.2 ± 5.8 kg/m². Patients from the PHPT group were significantly older (62.7 ±10.2 years vs 55 ± 11.9 years, P = 0.01), had a significantly higher serum calcium (10.9 ± 0.5 mg/dl vs 9.6 ± 0.3 mg/dl, P < 0.001), parathormone level [103.5 (89.9–147.1) pg/ml vs 44.9 (32.8–46.9) pg/ml, P < 0.001] and had more often prevalent fragility fractures (14.3% vs 6.5%, P = 0.35). Additionally, a significantly higher percentage of patients with PHPT had a value of TBS <1.350 (85.7% vs 58.1%, P = 0.03). Meanwhile, patients from the HT group had a significantly higher serum phosphorus (3.4 ± 0.3 mg/dl vs 2.7 ± 0.4 mg/dl, P < 0.001) and bone turnover markers, like alkaline phosphatase (107.6± 41.2 U/l vs 78.1 ± 23.4 U/l, P = 0.005) and P1NP (122.3 (55.1–156) ng/ml vs 70.2 (50.4–82.5) ng/ml, P = 0.007). We found that a TBS <1.350 had a sensitivity and specificity of 85.71% (95% CI, 63.66% to 96.95%) and 41.94% (95% CI, 24.55% to 60.92%), respectively, to predict bone fragility in patients with PHPT, with an accuracy of 59.62% (95% CI, 45.1% to 72.99%). However, there were no differences in BMD values on lumbar spine or hip between the two groups.

Conclusions: In conclusion, we found that patients with HT had higher bone turnover markers and patients with PHPT presented more often a TBS below 1.350. Thus, TBS could be a potential predictive marker for bone fragility in patients with PHPT.