Better way seen to measure bone loss, damage with Cushing’s disease

Trabecular bone score may accurately assess fracture risk in treated patients

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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A technique called trabecular bone score, or TBS, may be better at assessing bone damage and loss than bone mineral density, the current gold standard, in successfully treated patients with Cushing’s disease, according to a recent study.

High cortisol levels characterize Cushing’s, and they are known to increase the risk of fractures due to bone loss, particularly in the lumbar spine, its researchers noted.

The study, “Trabecular bone score (TBS) in Cushing’s disease: TBS gain after hypercortisolism normalization,” was published in the journal Bone.

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Areal bone mineral density is standard way of assessing fracture risk

High resolution CT and MRI scans are standard imaging tests that can be used to assess bone health. However, they require specialized equipment that often is not available in routine clinical practice.

The standard measure used to assess bone loss and fracture risk associated with high cortisol levels is the areal bone mineral density (aBMD), which is estimated using dual-energy X-ray absorptiometry, or DXA. However, aBMD cannot fully capture bone quality, including the small abnormalities in bone structure brought on by excessive cortisol, the scientists noted.

TBS, a technique also based on DXA, reflects bone microarchitecture and has been shown to better predict the risk of bone fractures in high-risk populations, such as menopausal women.

A high score in both aBMD and TBS indicates that bones are stronger and less prone to fracture.

Researchers in France evaluated changes in bone health using TBS and aBMD in Cushing’s disease patients who had been referred to a Paris hospital for a bone loss consultation between 2004 and 2019.

A total of 31 people (median age of 37.7) whose disease either was controlled or had been cured through surgical and/or medical treatment were analyzed.

Seventeen patients were cured after undergoing transsphenoidal surgery (TSS), a minimally invasive surgery used to remove tumors from the brain’s pituitary gland that cause Cushing’s disease, the study reported.

One patient was cured after undergoing bilateral adrenalectomy — a surgical procedure used to remove both adrenal glands — and another after receiving medical treatment exclusively. In eight cases, patients were cured after having both TSS and bilateral adrenalectomy, and in three cases after undergoing TSS in combination with medical treatment, it reported.

Study findings “support that bone microarchitecture is reduced in patients with [Cushing’s disease] and that this alteration in bone quality may be promptly restored after treatment,” the researchers wrote.

TBS seen to capture changes in bone microarchitecture with treatment

Seven patients had a history of bone fractures prior to treatment, and one-third had low bone mass as measured by aBMD.

Both TBS and aBMD significantly increased following Cushing’s cure: aBMD rose by 3.9% and TBS by 8.2%. No correlations were found between TBS and aBMD values before or after treatment.

Statistical analysis showed that a low TBS value at the start of treatment was predictive of improvements in bone health, as reflected by an increase in TBS values after treatment.

No variable, however, was predictive of aBMD gains following the disease’s cure.

Overall, these findings show that TBS is reduced in Cushing’s disease patients, reflecting a lower bone density. With treatment and cure, TBS significantly increases and its increase is higher than aBMD.

“The more significant improvement of microarchitecture assessed by TBS than aBMD and the absence of correlation between TBS and aBMD suggest that TBS may be an adequate marker of bone restoration after cure of [Cushing’s disease],” the researchers wrote.

“To support this conclusion, future studies with larger sample sizes and longer follow-up periods should be carried out,” they added.