Cushing’s patients have soft bones, even after remission: Study
Bone mineral density improves with remission, but hardness doesn’t
People with Cushing’s syndrome have soft bones, even after being in remission for a long time, a study reported.
Despite having comparable bone mineral density, a standard measure of bone health based on its mineral content, Cushing’s patients in remission scored significantly lower on the material strength index (BMSi), an assessment of bone hardness, than healthy individuals.
“These abnormalities, known to be associated with fractures in other populations, may play a role in the persistent bone fragility of steroid excess,” the researchers wrote
The study, “Bone Material Strength index is low in Patients with Cushing’s Syndrome even after long-term remission,” was published in the Journal of Clinical Endocrinology & Metabolism.
Cushing’s syndrome refers to a group of disorders characterized by excessive levels of cortisol, a steroid hormone that regulates several bodily processes, including metabolism and immune responses. Syndrome subtypes include Cushing’s disease, whereby tumors in the brain’s pituitary gland trigger the adrenal glands to produce too much cortisol. Sustainably high cortisol levels can lead to a wide range of symptoms, including bone loss and an increased risk of fractures.
Softer bones and fracture risk
A standard method to assess bone loss and fracture risk is to evaluate bone mineral density, or BMD, which measures the amount of calcium and other minerals in bones via a dual-energy X-ray absorptiometry scan. Studies suggest that up to 80% of people with Cushing’s have reduced BMD affecting the entire skeleton.
Although BMD improves upon disease remission, the rate of fractures among Cushing’s patients remains high, “suggesting that BMD may not adequately reflect fracture risk in this group,” the researchers wrote.
BMSi is a minimally invasive method of assessing bone hardness based on impact microindentation. Using a handheld device, the front surface of the lower leg bone (tibia) is indented with a probe that measures the resistance of bone tissue. With softer bone tissue, the probe more easily indents the bone, resulting in lower BMSi values.
A team of researchers at Leiden University Medical Center in the Netherlands tested the utility of BMSi to assess bone health in 60 people with Cushing’s who were in remission.
An equal number of healthy individuals, matched by age (median 56.5) and sex (48 women), were included as controls. The two groups were also matched by BMD at the lower spine and upper leg bone, and were comparable regarding the number of fragility (low-impact) fractures.
Patients had been in remission for a median of six years, with periods ranging from one to 41 years.
Despite comparable BMD measures, people with Cushing’s had markedly softer bones than controls, as indicated by a significantly lower mean BMSi value (76.2 vs. 80.5). Lower BMSi values significantly correlated with a higher body mass index, a measure of body fat content based on height and weight.
Still, BMSi values were not related to the presence of fractures, the use of hydrocortisone replacement therapy, other pituitary gland insufficiencies, or time since remission.
“Bone material properties remain altered in patients with [Cushing’s syndrome], even after long-term remission,” the research team wrote.
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