BMD may underestimate bone deterioration for women with endogenous Cushing’s syndrome
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Nearly one-third of women with endogenous Cushing’s syndrome and normal bone mineral density have a low trabecular bone score, according to study data.
“A large proportion of patients had degraded microarchitecture despite normal BMD,” Hiya Boro, DM, MD, MBBS, consultant in endocrinology, diabetes and metabolism at Aadhar Health Institute in India, and colleagues wrote. “The risk of fracture may be underestimated if BMD alone is measured. Hence, trabecular bone score should be added as a routine complementary tool in the assessment of bone health in patients with Cushing’s syndrome.”
Researchers conducted a cross-sectional study at a single center in India from March 2018 to August 2019. The study included 40 women with overt endogenous Cushing’s syndrome and 40 healthy sex-matched controls. Seum and salivary cortisol and plasma adrenocorticotropic hormone (ACTH) were measured. Participants were considered ACTH independent if they had a level of less than 2.2 pmol/L. Areal BMD was measured at the lumbar spine, femoral neck, total hip and distal one-third of the nondominant distal radius. Low BMD for age was defined as a z score of less than –2. Trabecular bone score was measured at the lumbar spine. Fully degraded microarchitecture was defined as a trabecular bone score of 1.2 or lower and partial degradation was a trabecular bone score of 1.21 to 1.34.
Of the 40 women with Cushing’s syndrome, 32 were ACTH-dependent and the other eight were ACTH independent. Of the independent group, seven had adrenal adenoma and one had adrenocortical carcinoma.
Women with Cushing’s syndrome had lower BMD at the lumbar spine (0.812 g/cm2 vs. 0.97 g/cm2; P < .001), femoral neck (0.651 g/cm2 vs. 0.773 g/cm2; P < .001) and total hip (0.799 g/cm2 vs. 0.9 g/cm2; P < .001) than the control group.
“No significant difference was noted in the distal radius BMD,” the researchers wrote. “This may be explained by the fact that cortisol excess predominantly affects trabecular rather than cortical bone.”
Absolute trabecular bone score was lower in the Cushing’s syndrome group compared with controls (1.2 vs. 1.361; P < .001). Based on trabecular bone score, 42.5% of women with Cushing’s syndrome had fully degraded bone microarchitecture, 45% had partially degraded microarchitecture and 12.5% had normal microarchitecture.
“In our study, 32.5% of patients had normal BMD with low trabecular bone score, thus highlighting the fact that patients may have normal BMD despite degraded microarchitecture,” the researchers wrote. “As such, assessment of BMD alone may underestimate the risk of fractures in patients with Cushing’s syndrome.”
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