Endocrine Abstracts

Background: Patients with acromegaly have an increased risk of vertebral fractures, yet normal or elevated bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA). This suggests that DXA may not be a reliable tool for assessing BMD in acromegalic patients. Multiple studies have suggested that patients with acromegaly have compromised trabecular bone but not cortical bone. Quantitative computed tomography (QCT) represents a three-dimensional technique for quantifying volumetric trabecular bone density, which is not affected by osteophytes and scoliosis commonly seen in acromegalic patients.

Objective: To examine the diagnostic discordance of osteoporosis between QCT and DXA in patients with acromegaly, and explore influencing factors of BMD in spine by DXA and QCT, separately.

Methods: We enrolled patients diagnosed with acromegaly consecutively at West China Hospital between January 2021 and December 2023, and excluded patients with plurihormonal PIT-1 positive pituitary adenoma. The diagnostic criteria established by the World Health Organization in 1994 for DXA were employed to diagnose osteoporosis and osteopenia, while the criteria endorsed by the International Society of Clinical Densitometry were utilized for QCT. Minor discordance was defined as the presence of adjacent diagnostic classes between the two techniques, whereas major discordance arose when one method diagnosed osteoporosis while the other indicated normal bone health.

Results: We enrolled 53 participants (28 females/25 males), with a median age of 44 years old. Three participants were diagnosed with osteoporosis/low bone mass by DXA, and 5 with osteoporosis by QCT. Major discordance, minor discordance, and concordance in diagnoses between the two techniques were 3.8%, 18.9%, and 77.4%, respectively. Patients consistently diagnosed with osteoporosis had higher age (59 vs 42 years old, P<0.005) and lower BMD by QCT (110.1 g/cc vs 153.8 g/cc, P<0.005) compared to patients without discordant diagnoses. Multiple linear regression analyses showed that age (β=-0.516, P<0.005), body mass index (β=-0.209, P=0.024), growth hormone (β=0.187, P=0.023), and female (β=-0.178, P=0.039) were independent factors of BMD by QCT, while none of them were independent factors of BMD by DXA. The adjusted R2 of this model was 0.429.

Conclusion: Our study demonstrated that QCT might be a more sensitive tool to assess bone health in patients with acromegaly, especially in those who are younger and have less severe bone loss. BMD data by QCT can be largely explained by clinical features of acromegalic patients but not by DXA, which suggests that QCT may be a superior diagnostic tool in this population compared with DXA.