What is the utility of distal forearm DXA in primary hyperparathyroidism?

Primary hyperparathyroidism (PHPT) leads to increased bone turnover, low bone mineral density, and increased fracture risk. These effects are, however, preferentially seen in the distal forearm, which is rich in cortical bone. This study aimed to determine how frequently the distal forearm T score was the worst T score and if this T score alone led to higher rate of diagnosis of osteopenia or osteoporosis.

We retrospectively reviewed a prospective database of 300 patients undergoing parathyroidectomy at our institution between November 2000 and January 2009. The bone mineral density of the lumbar spine, total proximal femurs, and distal third of the nondominant radius was measured by dual x-ray absorptiometry. Data on bone density are reported as T scores.

The mean T scores were -1.30 ± 0.2 in the distal forearm, -1.0 ± 0.1 in the total proximal femurs, and -0.9 ± 0.1 in the spine. The distal forearm T score was the worst bone mineral density T score in 39% of patients. This T score alone led to an upstaging in diagnosis to osteopenia or osteoporosis in 9.4% of patients.

In patients with PHPT, the worst T score is commonly found in the distal forearm. This T score can identify additional patients with a diagnosis of osteopenia or osteoporosis. Distal forearm bone mineral density should, therefore, be assessed in all patients who have a diagnosis of PHPT.