Assessment of Inner Bone Layer Better at Detecting Bone Damage in Cushing’s, Study Shows

A noninvasive and inexpensive technique could help improve the clinical assessment of bone damage in Cushing’s syndrome patients, a French study reports.

The approach, called trabecular bone score, was better at detecting bone damage in these patients than the standard bone mineral density assessments.

The study, “Assessment of vertebral microarchitecture in overt and mild Cushing’s syndrome using trabecular bone score,” appeared in the journal Clinical Endocrinology.

Research has shown that bone fractures in Cushing’s syndrome may occur despite normal or only slightly reduced bone mineral density. In fact, scientists have found that excessive levels of glucocorticoids have a greater impact on the bone’s fine architecture — specifically on the volume of the bone’s inner layer, called the trabecular bone — than on bone mineral density.

Current techniques for studying bone microarchitecture are not compatible with routine clinical management. An alternative is using trabecular bone score (TBS), a texture measurement derived from 2D images obtained during a bone scan.

Studies on osteoporosis have suggested that TBS predicts the risk of bone fractures. Additionally, reports from patients taking glucocorticoids showed that alterations in TBS were more common than those in bone mineral density, and were more effective for assessing bone properties. The limited evidence from cases of endogenous Cushing’s syndrome — caused by the body’s own overproduction of cortisol — are in line with these results, but more research is needed.

Scientists in this study compared lumbar spine bone mineral density and TBS in 110 cases of overt Cushing’s syndrome and mild autonomous cortisol secretion (MACE), and assessed changes in bone mineral density and TBS in a subset of patients in remission.

Specifically, the study included 53 patients with Cushing’s — 35 with Cushing’s disease, 11 with bilateral adrenal masses, and seven with ectopic (outside the pituitary) secretion of the adrenocorticotropin hormone (ACTH) — 39 with MACE, and 18 with non-secreting adrenal incidentaloma, which is an incidentally found adrenal mass. Fourteen patients with overt Cushing’s syndrome were followed for up to two years after cure.

Results from the Cushing’s subgroup revealed that 24% of patients showed vertebral osteoporosis through bone mineral density, while 43% had degraded microarchitecture with TBS. Comparisons of patients with MACE with those with non-secreting incidentalomas revealed differences in TBS, but not in bone mineral density.

Data also indicated that overt bone fractures tended to be associated with low TBS, but not with low bone mineral density. TBS, but not bone mineral density, decreased with the intensity of hypercortisolism (excessive production of cortisol) in all patient subgroups. Results further revealed that TBS improved more markedly and rapidly than bone mineral density following remission.

“TBS may be a promising, non-invasive, widely available and inexpensive complementary tool for the routine assessment of the impact of CS,” the researchers wrote.

Regarding the improvements in TBS after remission of Cushing’s syndrome, the investigators said that “despite a limited number of patients and duration of follow up, our findings suggest that TBS is also much more sensitive to variations in endogenous glucocorticoids both in excess and after withdrawal.”