Lower thoracic muscle mass is associated with lesser bone mineral density (BMD) gain after parathyroidectomy in patients with primary hyperparathyroidism (PHPT), researchers reported in the Journal of Clinical Endocrinology & Metabolism.

The investigators sought to determine whether thoracic muscle mass levels secondarily assessed with preoperative noncontrast parathyroid single photon emission/computed tomography (SPECT)/CT scans could be used to predict bone density changes after parathyroidectomy in patients with PHPT.

The cohort study included electronic medical record data from a hospital in Seoul, Korea, from November 2012 to January 2021. All patients included in the final analysis had sporadic asymptomatic PHPT with at least 1 surgical indication.


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Thoracic muscle volume at the T6 to T7 levels was estimated with SPECT/CT scans and an automated deep-learning–based software. The median duration between pre- and postoperative dual-energy X-ray absorptiometry (DXA) measurement was 391.5 days (interquartile range, 370-458). Annualized femoral neck BMD change was the primary outcome of estimated surgical response post-parathyroidectomy.

A total of 130 patients with PHPT who had parathyroidectomy postparathyroid SPECT/CT (mean age, 64.7±8.5 years; 81.5% female) were included.

A weak, positive correlation was found between thoracic skeletal muscle mass and baseline BMD at the lumbar spine (r = 0.43, P < .001), femoral neck (r = 0.48, P < .001), and total hip (r = 0.49, P < .001). Lower thoracic muscle mass was associated with elevated preoperative parathyroid hormone (PTH) levels. A 1 log-unit increment in PTH was associated with a 8.51 cm3 reduction in thoracic muscle mass, independent of age, sex, body mass index (BMI), and baseline femoral neck BMD.

Bone mineral density values at the lumbar spine, femoral neck, and total hip significantly increased 1 year after parathyroidectomy (P < .001 for all values).

Lower baseline thoracic skeletal muscle mass values were associated with a lesser annual percentage BMD gain at the femoral neck (adjusted β: -2.35 %/year per SD decrement, P = .034), and lumbar spine (adjusted β: -2.51 %/year per SD decrement, P = .044), after adjustment for age, sex, BMI, preoperative PTH level, and baseline BMD.

The association between lower thoracic skeletal muscle mass and lesser BMD gain after parathyroidectomy was still robust in the femoral neck and lumbar spine after individual differences in baseline BMD were controlled in random effects modeling in the linear mixed models (per 1 SD decrement in thoracic skeletal muscle mass; femoral neck BMD, -2.34%/year; 95% CI, -4.21 to -0.48; P = .014; lumbar spine BMD, -2.51%/year; 95% CI, -4.45 to -0.57; P = .011).

Among several limitations, the researchers noted that residual confounders cannot be excluded owing to the retrospective design, and the study was limited to Korean patients who underwent surgical treatment. They also cautioned that the findings cannot be interpreted as mandating the use of SPECT/CT as the first-line preoperative localization modality in patients with PHPT.

“This proof-of-concept study supports the potential clinical importance of preoperative investigation for skeletal muscle mass and function in patients with PHPT,” the investigators commented. “DXA-based whole body composition assessment along with simple muscle function tests such as handgrip strength can be incorporated in routine preoperative evaluation for PHPT, which needs to be tested further.”

Reference

Burm SW, Hong N, Lee S, et al. Preoperative thoracic muscle mass predicts bone density change after parathyroidectomy in primary hyperparathyroidism. J Clin Endocrinol Metab. Published online February 11, 2022. doi:10.1210/clinem/dgac083