Primary hyperparathyroidism (PHPT) results in decreased bone mineral density (BMD) and increased fracture risk, even in asymptomatic patients with incidentally detected mild disease.1,2 Preferential involvement of cortical bone with relative preservation of the trabecular bone has been described in PHPT.3,4 The incidence of morphometric vertebral fractures is increased, even in patients who maintain normal lumbar BMD.5,6⁠ International guidelines recommend a better characterization of the bone involvement of the asymptomatic patient to indicate surgery. In addition to the study of BMD by dual x-ray absorptiometry (DXA), including the forearm, the guidelines advise investigating the presence of radiological vertebral fractures and the study of bone microstructure by trabecular bone score (TBS) if available.7, 8, 9, 10, 11 However, although the guidelines recognize that TBS can be useful in the diagnosis of bone involvement in PHPT, they do not establish surgical criteria based on the value of this index.12, 13, 14

Successful parathyroidectomy (PTX) leads to the normalization of serum calcium and parathyroid hormone (PTH). Patients who underwent PTX, compared to patients without surgery, showed a significant increase in BMD at the lumbar spine (LS), femoral neck (FN), and total hip (TH) whereas there was a decline at the forearm BMD that was less significant in the PTX group than in the observation group.15, 16, 17, 18 Although published studies suggest that surgery would decrease the risk and frequency of vertebral and nonvertebral fractures, only large randomized controlled studies with prolonged follow-up could confirm this.18, 19, 20, 21 Despite the recommendation of international guidelines on the indication for surgery in patients with asymptomatic PHPT, the decision of which patients should undergo surgery remains the subject of studies and a frequent concern in routine clinical practice.22, 23, 24 Clinical research with TBS and three-dimensional densitometry (3D-DXA), which provide information on bone quality, could improve our understanding of skeletal characteristics in PHPT before and after curative surgery and may be useful in learning which patients may benefit most from surgery.11

This study aimed to evaluate the bone microstructure to determine whether surgery of PHPT produces changes in both BMD and bone measures related to bone quality, such as TBS and 3D-DXA. The changes detected by these techniques were compared, identifying the variables that undergo the largest change after surgery. In addition, we searched for the clinical and analytical variables with the strongest relationship in the changes produced in BMD, TBS, and 3D-DXA after surgery.