The changes of standard DXA measurements and TBS depending on outcomes of neurosurgical treatment in patients with Cushing's disease

Abstract

BACKGROUND: Patients with endogenous hypercortisolism have reduced bone mineral density (BMD) and trabecular bone score (TBS) that are the causes of secondary osteoporosis and low-traumatic fractures. It is well known that radical treatment (neurosurgery or radiosurgery) of Cushing’s disease leads to a decline of cortisol levels in all body fluids to normal values. However, it is still uncertain whether bone tissue structure, and particularly its microarchitecture, does recover in remission of the disease.
 AIMS: To evaluate an influence of hormone activity (presence or absence of remission) in patients with Cushing's disease on changes of bone structure measurements in accordance with DXA values (TBS, BMD, T- and Z-scores), as well as significance of such changes in 12 and 24 months after neurosurgical treatment.
 MATERIALS AND METHODS: In patients with confirmed active Cushing's disease (ACTH-producing pituitary adenoma) (n = 44) and in control group of healthy volunteers (n = 40), BMD in lumbar spine (L1-L4) and simultaneously TBS, in cut-off points before neurosurgical treatment (in both groups) and in 12 and 24 months after it (only in patients), were assessed. We diagnosed presence or absence of disease remission at cut-offs. All measurements were performed using a GE iDXA device (GE Healthcare Lunar, Madison, Wisconsin, USA). The TBS was calculated simultaneously from taken BMD scans, blinded to clinical outcome using TBS iNsight software v2.1 (Medimaps, Merignac, France). The activity of Cushing’s disease was evaluated using late-night salivary cortisol (LNSC, at 23:00). To determine the differences in DXA and TBS values before and after neurosurgical intervention depending on remission occurrence, covariate analysis (ANCOVA) was applied.
 RESULTS: There were found significant changes in TBS, BMD and T-score values in 12 months after neurosurgical treatment associated with presence or absence of disease remission (p = 0.039, 0.046 and 0.048, respectively). No differences in Z-score as well as in all measurements in 24 months, that might be associated with remission occurrence, were revealed. The gain in all DXA measurements (including TBS) during 24 months of observation period was statistically significant when analyzing data using Student’s paired t-test. However, the values corresponding to the age references had not been achieved for the specified time interval.
 CONCLUSIONS: Patients with Cushing’s disease have lower TBS values. In remission conditions TBS is getting significantly higher. The increase in BMD and TBS occurs during 24 months after achieving remission of Cushing’s disease but doesn’t lead to a full restoration of normal bone mass and microstructure throughout observation period of 24 months.